OptiStruct 2019 Tutorials [PDF]

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Altair OptiStruct 2019

Tutorials

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Contents Intellectual Property Rights Notice............................................................................. v Technical Support............................................................................................................ ix Accessing the Model Files............................................................................................ 11 Run OptiStruct from HyperMesh................................................................................. 12 Run OptiStruct at the Command Line....................................................................... 18 Basic Small Displacement Finite Element Analysis................................................ 19 OS-T: 1000 Linear Static Analysis of a Plate with a Hole...................................................... 20 OS-T: 1010 Thermal Stress Analysis of a Coffee Pot Lid.......................................................35 OS-T: 1020 Normal Modes Analysis of a Splash Shield.........................................................45 OS-T: 1030 3D Inertia Relief Analysis................................................................................55 OS-T: 1040 3D Buckling Analysis...................................................................................... 64 OS-T: 1050 Connection of Dissimilar Meshes using CWELD Elements..................................... 73 OS-T: 1060 Analysis of a Composite Aircraft Structure using PCOMPG.................................... 83 OS-T: 1070 Analysis of an Axi-symmetric Structure.............................................................95 OS-T: 1080 Coupled Linear Heat Transfer/Structure Analysis...............................................103 OS-T: 1085 Linear Steady-state Heat Convection Analysis.................................................. 116 OS-T: 1090: Linear Transient Heat Transfer Analysis of an Extended Surface Heat Transfer Fin........................................................................................................... 127 OS-T: 1100 Thermal Stress Analysis of a Printed Circuit Board with Anisotropic Material Properties......................................................................................................... 152 OS-T: 1110 Modal Analysis Setup....................................................................................159

Advanced Small Displacement Finite Element Analysis...................................... 165 OS-T: 1300 Direct Frequency Response Analysis of a Flat Plate........................................... 166 OS-T: 1305 Modal Frequency Response Analysis of a Flat Plate........................................... 177 OS-T: 1310 Direct Transient Dynamic Analysis of a Bracket................................................ 189 OS-T: 1315 Modal Transient Dynamic Analysis of a Bracket................................................ 197 OS-T: 1320 Nonlinear Gap Analysis of an Airplane Wing Rib............................................... 206 Exercise 1: Linear Gap Analysis...............................................................................206 Exercise 2: Nonlinear Gap Analysis.......................................................................... 213 Analysis Review..................................................................................................... 218 OS-T: 1325 Random Response Analysis of a Flat Plate....................................................... 219 OS-T: 1330 Acoustic Analysis of a Half Car Model............................................................. 226

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OS-T: 1340 Fatigue (Stress - Life) Method....................................................................... 239 Fatigue using S-N (Stress - Life) Method.................................................................. 239 Fatigue Process Manager (FPM) using S-N (Stress - Life) Method................................. 249 OS-T: 1350 Fatigue (Strain - Life) Method........................................................................263 Fatigue using E-N (Strain - Life) Method.................................................................. 263 Fatigue Process Manager (FPM) using E-N (Strain - Life) Method..................................273 OS-T: 1360 NLSTAT Analysis of Gasket Materials in Contact................................................289 OS-T: 1365 NLSTAT Analysis of Solid Blocks in Contact...................................................... 302 OS-T: 1370 Complex Eigenvalue Analysis of a Reduced Brake System.................................. 316 OS-T: 1371 Brake Squeal Analysis of Brake Assembly........................................................321 OS-T: 1372 Rotor Dynamics of a Hollow Cylindrical Rotor................................................... 327 OS-T: 1375 Response Spectrum Analysis of a Structure..................................................... 334 OS-T: 1380 Computation of Equivalent Radiated Power...................................................... 344 OS-T: 1385 Heat Transfer Analysis on Piston Rings with GAP Elements................................. 349 OS-T: 1390 Pretensioned Bolt Analysis of an IC Engine Cylinder Head, Gasket and Engine Block System............................................................................................... 357 OS-T: 1392 Node-to-Surface vs Surface-to-Surface Contact................................................ 379 OS-T: 1393 Basics of Contact Properties and Debugging.................................................... 390

Large Displacement Finite Element Analysis......................................................... 399 OS-T: 1500 Nonlinear Implicit Analysis of Bending of a Plate.............................................. 400 OS-T: 1510 Follower Loads, Nonlinear Adaptive Criteria, and Nonlinear Intermediate Results...................................................................................................... 413 OS-T: 1520 Finite Sliding of Rack and Pinion Gear Model....................................................428

Fluid-Structure Interaction Analysis........................................................................ 436 OS-T: 1600 Fluid-Structure Interaction Analysis of Piezoelectric Harvester Assembly............... 437 OS-T: 1610 Thermal Fluid-Structure Interaction Analysis on a Manifold.................................449

Multibody Dynamics Analysis.....................................................................................457 OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T:

1900 Dynamic Analysis of a Three-body Model........................................................ 458 1910 Dynamic Analysis of a Slider Crank with Flexible Connecting Rod........................ 469 1920 Large Displacement Analysis of a Cantilever Beam............................................485 1930 Generating Flexible Body for use in MotionSolve...............................................495 1940 MBD Rigid Contact....................................................................................... 501 1950 Curve to Curve Constraint............................................................................. 510 1960 Defining Point to Deformable Curve Joint........................................................ 519

Topology Optimization................................................................................................. 528 OS-T: 2000 Design Concept for a Structural C-Clip............................................................ 529 OS-T: 2005 Design Concept for a Structural C-Clip with Minimum Member Size Control........... 545 OS-T: 2010 Design Concept for an Automotive Control Arm................................................549

2

OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T:

2020 Increasing Natural Frequencies of an Automotive Splash Shield with Ribs............. 563 2030 Control Arm with Draw Direction Constraints................................................... 577 2040 Spot Weld Reduction using CWELD and 1D...................................................... 585 2050 Pattern Repetition.........................................................................................589 2060 Symmetry and Draw Direction Constraints Applied Simultaneously...................... 598 2070 Reduced Model using DMIG........................................................................... 605 2080 Hook with Stress Constraints......................................................................... 618 2090 Extrusion Constraints.................................................................................... 625 2095 Frequency Response Optimization of a Rectangular Plate................................... 631 2098 Excavator Arm............................................................................................. 651

Topography Optimization............................................................................................ 658 OS-T: OS-T: OS-T: OS-T:

3000 3010 3020 3030

Topography Optimization of a Plate Under Torsion.............................................659 Topography Optimization of an L-bracket.........................................................670 Automatic Recognization of Bead Results of an L-Bracket...................................678 Random Response Optimization..................................................................... 684

Combination Optimization...........................................................................................691 OS-T: 3100 Combined Topology and Topography Optimization of a Slider Suspension..............692 OS-T: 3200 Design of a Composite Aircraft Underbelly Fairing............................................. 700 Phase 1: Reference Design Synthesis (Free-Size Optimization).................................... 701 Phase 2: Design Fine Tuning (Size Optimization)....................................................... 714 Phase 3: Ply Stacking Sequence Optimization........................................................... 721 OS-T: 3300 Lattice Optimization Process.......................................................................... 726 Phase 1: Reference Level Design............................................................................. 727 Phase 2: Design Fine Tuning...................................................................................733 OS-T: 3400 Design an Open Hole Tension (OHT)............................................................... 741 Model Setup and Baseline Analysis.......................................................................... 742 Phase 1: Reference Design Synthesis (Free-size Optimization).....................................751 Phase 2: Design Fine Tuning (Size Optimization)....................................................... 764 Phase 3: Ply Stacking Sequence Optimization........................................................... 771 Performing a Final Post-Optimization Analysis............................................................774

Size Optimization.......................................................................................................... 778 OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T:

4000 4010 4020 4030 4040 4050 4070 4080 4090

3D Size Optimization of a Rail Joint................................................................779 Size Optimization of a Welded Bracket............................................................ 788 Composite Bike Frame Optimization................................................................796 Discrete Size Optimization of a Welded Bracket................................................ 806 Size Optimization of a Shredder.....................................................................814 Optimization of a Horizontal Tail Plane............................................................ 827 Free-sizing Nonlinear Gap Optimization on an Airplane Wing Rib......................... 856 Minimization of the Maximum Stress of a Rotating Bar...................................... 865 Manufacturing Constraints of a Composite Structure......................................... 872

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OS-T: 4095 Size Optimization using External Responses (DRESP3)...................................... 883

Shape Optimization.......................................................................................................890 OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T: OS-T:

5000 2D Shape Optimization of a Cantilever Beam................................................... 891 5010 Cantilever L-beam Shape Optimization............................................................ 902 5020 3D Bracket Model using the Free-shape Method............................................... 910 5030 Buckling Optimization of a Structural Rail........................................................ 923 5040 Rail Joint.....................................................................................................933 5050 4 Bar Linkage.............................................................................................. 953 5060 3D Model using the Free-shape Method with Manufacturing Constraints................964 5070 Fatigue Optimization of a Torque Control Arm.................................................. 972 5080 Global Search Optimization............................................................................983 5090 Thermal Optimization on Aluminum Fins......................................................... 989

Index.................................................................................................................................995

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Accessing the Model Files Accessing the Model Files

Required model files are available online. 1. To access model files, visit Altair Connect or the Altair Client Center. A user ID and password are required to access the model files. Follow the instructions at the website to obtain login credentials. 2. Select the required file package and download it onto your system. Note: The files may require unzipping before proceeding with the tutorials. When extracting zipped files, preserve any directory structure included in the file package.

1

Run OptiStruct from HyperMesh

2

Run OptiStruct from HyperMesh

This chapter covers the following: •

Launching HyperMesh and Setting the OptiStruct User Profile (p. 13)

•

Opening the Model (p. 14)

•

Submitting the Job (p. 15)

•

Post-processing the Results (p. 17)

This tutorial demonstrates how to launch an OptiStruct job from within HyperMesh. A HyperMesh database containing a fully defined OptiStruct finite element model is retrieved and an OptiStruct job is launched from the OptiStruct panel in HyperMesh.

OptiStruct Tutorials Run OptiStruct from HyperMesh

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the plate.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The plate.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 1: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter plate for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the plate.fem was written. The plate.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: plate.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. plate.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. plate.h3d HyperView binary results file.

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OptiStruct Tutorials Run OptiStruct from HyperMesh plate.res HyperMesh binary results file. plate.stat Summary, providing CPU information for each step during analysis process.

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OptiStruct Tutorials Run OptiStruct from HyperMesh

Post-processing the Results While still in HyperMesh, launch HyperView after the job has finished from the OptiStruct panel. Click HyperView. HyperView opens and automatically loads the H3D file from the OptiStruct job for post-processing.

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Run OptiStruct at the Command Line

3

Run OptiStruct at the Command Line

The tutorial Running OptiStruct from HyperMesh demonstrates how OptiStruct could be launched from within HyperMesh. OptiStruct also can be run at the command line (Unix or MSDOS). This tutorial assumes you already have the running file, plate.fem, in either your Unix or MSDOS directory. This tutorial also assumes you know the location of the solver script. In this tutorial, $HWSDIR describes the directory containing the OptiStruct executable. On Unix machines, the script is normally located in the HyperWorks installation directory under /scripts/. On Windows, it is normally located in the HyperWorks installation directory under /hwsolvers/scripts/. Running OptiStruct from the Command Line (Unix or MSDOS).

From the Command Prompt $HWSDIR/ plate.fem

Check Current Version at the Command Prompt $HWSDIR/ -version

Execute a Check Run to Validate Input Deck $HWSDIR/ plate.fem -check Information regarding memory requirements is written to the file plate.out. See Run OptiStruct in the User Guide for more detailed information.

Basic Small Displacement Finite Element Analysis Basic Small Displacement Finite Element Analysis

This chapter covers the following: •

OS-T: 1000 Linear Static Analysis of a Plate with a Hole (p. 20)

•

OS-T: 1010 Thermal Stress Analysis of a Coffee Pot Lid (p. 35)

•

OS-T: 1020 Normal Modes Analysis of a Splash Shield (p. 45)

•

OS-T: 1030 3D Inertia Relief Analysis (p. 55)

•

OS-T: 1040 3D Buckling Analysis (p. 64)

•

OS-T: 1050 Connection of Dissimilar Meshes using CWELD Elements (p. 73)

•

OS-T: 1060 Analysis of a Composite Aircraft Structure using PCOMPG (p. 83)

•

OS-T: 1070 Analysis of an Axi-symmetric Structure (p. 95)

•

OS-T: 1080 Coupled Linear Heat Transfer/Structure Analysis (p. 103)

•

OS-T: 1085 Linear Steady-state Heat Convection Analysis (p. 116)

•

OS-T: 1090: Linear Transient Heat Transfer Analysis of an Extended Surface Heat Transfer Fin (p. 127)

•

OS-T: 1100 Thermal Stress Analysis of a Printed Circuit Board with Anisotropic Material Properties (p. 152)

•

OS-T: 1110 Modal Analysis Setup (p. 159)

4

OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

p.20

OS-T: 1000 Linear Static Analysis of a Plate with a Hole This tutorial demonstrates the creation of finite elements on a given CAD geometry of a plate with a hole. Further, application of boundary conditions and a finite element analysis of the problem are explained. Post-processing tools are used in HyperView to determine deformation and stress characteristics of the loaded plate.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the plate_hole.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The plate_hole.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating the Material 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter steel.

3. Set Card Image to MAT1. 4. Enter the material values next to the corresponding fields. a) For E (Young's Modulus), enter 2.1E+05.

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b) For NU, (Poisson's Ratio), enter 0.3.

c) For RHO (Mass Density), leave it undefined since only a static analysis is performed.

Figure 2: Material Property Values for steel

A new material, steel, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Creating the Property 1. In the Model Browser, right-click and select Create > Property from the context menu. A default property displays in the Entity Editor. 2. For Name, enter plate_hole. 3. Set Card Image to PSHELL.

4. Enter the property values next to the corresponding fields. An empty Value field indicates that it is turned off. To edit these properties, click on the blank Value fields next to them and enter the required values. a) For Material, click Unspecified > Material. In the Select Material dialog, select steel and click OK. b) For T (thickness of the plate), enter 10.0.

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Figure 3: Property Values for plate_hole

A new property, plate_hole, has been created as a 2D PSHELL. Material information is also linked to this property.

Updating the plate_hole Component 1. In the Model Browser, click on the component plate_hole. The component fields are displayed in the Entity Editor below. 2. For Property, click Unspecified > Property. In the Select Property dialog, select plate_hole and click OK.

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Figure 4:

The component plate_hole has been updated with a property of the same name, and is now the current component. This component uses the plate_hole property definition with a thickness value of 10.0. The material steel is referenced by this component.

Applying Loads and Boundary Conditions In the following steps, the model is constrained so that two opposing edges of the four external edges cannot move. The other two edges remain unconstrained. A total load of 1000N is applied at the edge of the hole in the positive z-direction.

Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter spcs.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. A new load collector, spcs is created.

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Figure 5: Creating the spcs Load Collector

5. Create another load collector. a) For Name, enter forces.

b) For Card Image, select None.

Creating Constraints 1. In the Model Browser, Load Collectors folder, right-click on spcs and select Make Current to set spcs as the current load collector.

Figure 6: Setting spcs as the Current Load Collector

2. From the menu bar, click BCs > Create > Constraints to open the Constraints panel.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

Figure 7: Accessing the Constraints Panel

3. Make sure nodes is selected from the entity selection switch.

Figure 8: Menu after Clicking on the Entity Selection Switch

4. Hold Shift while clicking-and-dragging your mouse to select the nodes on the two ends of the plate.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

Figure 9: Nodes to Select for the Constraints

5. Constrain dof1, dof2, dof3, dof4, dof5, and dof6 and set all of them to a value of 0.0. • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom.

Figure 10: Constraining all Degrees of Freedom of the Selected Nodes

6. Click create. Constraints are applied to the selected nodes. 7. Click return to go back to the main menu.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

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Creating Forces on the Nodes around the Hole 1. In the Model Browser, set your current load collector to forces. 2. From the menu bar, click BCs > Create > Forces to open the Forces panel. 3. Press Shift while left-clicking, then release your mouse button to access selection options. Select Circle Interior.

Figure 11: Choosing a Circular (Inside of Circle) Selection Window

4. Hold Shift while clicking-and-dragging your mouse to select the nodes around the hole.

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Figure 12: Nodes Selected for the Application of Loads around the Hole

5. Define settings in the Forces panel. a) Set the coordinate system toggle to global system. b) Set the vector definition switch to constant vector. c) In the magnitude= field, enter 21.277 (that is 1000 divided by the number of nodes 47). d) Set the direction definition switch, below magnitude =, to z-axis.

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Figure 13: Assigning Direction and Magnitude to the Forces

6. Click create. Point forces, with the given magnitude in the z-direction, are applied to the selected nodes about the hole. 7. Click return to go back to the main menu.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter lateral forces.

3. Set Analysis type to Linear Static. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select spcs and click OK. 5. Define LOAD. a) For LOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select forces and click OK. An OptiStruct subcase has been created which references the constraints in the load collector spcs and the forces in the load collector forces.

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Figure 14: Creating the lateral forces Loadstep

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 15: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter plate_hole for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the plate_hole.fem was written. The plate_hole.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: plate_hole.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. plate_hole.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. plate_hole.h3d HyperView binary results file. plate_hole.res HyperMesh binary results file. plate_hole.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results Displacement and Stress results for linear static analyses are output from OptiStruct by default. The following steps describe how to view those results in HyperView. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data.

Viewing a Contour Plot of Stresses 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. On the Results toolbar, click

to open the Contour panel.

3. Define settings in the Contour panel.

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a) Under Result type set the first first pull-down menu to Element Stresses (2D & 3D) (t) and set the second pull-down menu to vonMises. b) Set the Averaging method to None.

Figure 16: The Contour panel

4. Click Apply. A contoured image representing von Mises stresses should be visible. Each element in the model is assigned a legend color, indicating the von Mises stress value for that element, resulting from the applied loads and boundary conditions. 5. In the View Controls toolbar, click the XY Top Plane View icon to change the view the model.

Figure 17: The vonMises Stress Plot for the Given Subcase

Try to answer the following questions to test your understanding of the current problem. • What is the maximum von Mises stress value? • At what location does the model have its maximum stress? • Does this make sense based on the boundary conditions applied to the model?

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Viewing a Contour Plot of Displacements 1. Under Result type set the first first pull-down menu to Displacement (v) and set the second pulldown menu to Mag. 2. Click Apply. The resulting contours represent the displacement field resulting from the applied loads and boundary conditions. Try to answer the following questions to test your understanding of the current problem. • What is the maximum Displacement value? • At what location does the model have its maximum displacement? • Does this make sense based on the boundary conditions applied to the model?

Viewing the Deformed Shape 1. In the View Controls toolbar, click the Isometric View icon to display the isometric view of the model. 2. Click the Deformed toolbar icon

.

3. Define settings in the Deformed panel. a) Set Result type to Displacement(v). b) Set Scale to Scale factor. c) Set Type to Uniform. d) For Value, enter 500.

This means that the displacement results of the analysis is multiplied by 500.

e) Under Undeformed shape, set Show to Wireframe. 4. Click Apply. A deformed plot of the model with the displacement contour should be visible, overlaid on the original undeformed mesh in isometric view.

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Figure 18: Isometric View of the Deformed Plot Overlaid on the Undeformed Mesh (Model Unit is Set to 500)

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OS-T: 1010 Thermal Stress Analysis of a Coffee Pot Lid In this tutorial, an existing finite element model of a plastic coffee pot lid demonstrates how to apply constraints and perform an OptiStruct finite element analysis. HyperView post-processing tools are used to determine deformation and stress characteristics of the lid.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the coffee_lid.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The coffee_lid.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating the Material The model has two component collectors with no materials. A material collector needs to be created and assigned to the component collectors. 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter plastic. 3. Set Card Image to MAT1.

4. Enter the material values next to the corresponding fields.

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a) For E (Young's Modulus), enter 1137.

b) For NU, (Poisson's Ratio), enter 0.26.

c) For A (coefficient of linear thermal expansion), enter 8.1e-005.

d) For RHO (Mass Density), leave it undefined since only a static analysis is performed.

Figure 19: Material Property Values for plastic

A new material, plastic, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Editing the PSHELL Property 1. In the Model Browser, Properties folder, click PSHELL. The PSHELL property entry is displayed in the Entity Editor. 2. Verify that the thickness value, T, is set to 2.5. 3. For Material, click Unspecified > Material. Notice: The Value field next to Material is set to . This indicates that no material properties are being referenced by this property.

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Figure 20: Selecting the Material plastic for the Property PSHELL

4. In the Select Material dialog, select plastic and click OK. The material plastic is now assigned to the property PSHELL.

Figure 21: The PSHELL Property Entry Fields in the Entity Editor

5. Assign the material plastic to the property PSHELL1. The property collectors and component collectors, PSHELL and PSHELL1, now reference the material plastic. The component collectors that reference the corresponding properties are automatically updated with the specified material. If you access the Entity Editor and edit either of these property or component collectors, notice that the Material fields are now all set to plastic.

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Applying Loads and Boundary Conditions Thermal loading has already been applied to the model. In the following steps, constraints will be applied to the model.

Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter constraints.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. A new load collector, constraints is created.

Figure 22: Creating the constraints Load Collector

Creating Constraints at the Corners of the Spout Cut-out 1. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 2. Set the entity selector to nodes, then select the two nodes at the corners of the spout cut-out.

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Figure 23: Selecting Nodes for Constraints at Corners of Spout Cut-Out

3. Constrain only DOF3. • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 4. Click create. Two constraints are created. Constraint symbols (triangles) appear in the graphics area at the selected nodes. The number 3 is written beside the constraint symbol, indicating the DOF constrained. 5. In the size field, enter 1.0. The size of the constraint symbols in the modeling window change. 6. Click return to go back to the main menu.

Creating Constraints Opposite the Spout Cut-Out 1. From the menu bar, click Geometry > Create > Nodes > XYZ to open the Nodes: XYZ panel. 2. In the XYZ panel, define coordinates for the node. a) In the x field, enter 0.0.

b) In the y field, enter -10.0. c) In the z field, enter 0.0.

3. Click create. A node is created with the coordinates (0, -10, 0). This indicates the centerline of the coffee lid. 4. Click return to go back to the main menu.

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5. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 6. Using the entity selector, select the nodes indicated in Figure 24.

Figure 24: Creating Constraints Opposite the Spout Cut-Out to Model Hinges

7. Constrain only dof1, dof2, and dof3. 8. Click create. Four constraints are created. Again, this is verified by the appearance of constraint symbols in the modeling window. 9. Click return to go back to the main menu. 10. From the Geom page, select the temp nodes panel. 11. Click clear all. The temporary node that was created at (0, -10, 0) is removed. 12. Click return.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter brew cycle.

3. Set Analysis type to Linear Static. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select constraints and click OK. 5. Define TEMP. a) For TEMP, click Unspecified > Loadcol.

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b) In the Select Loadcol dialog, select THERMAL_LOADING and click OK. An OptiStruct subcase has been created which references the constraints in the load collector constraints and the forces in the load collector THERMAL_LOADING.

Figure 25: Creating the brew cycle Loadstep

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 26: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter lid_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the lid_complete.fem was written. The lid_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: lid_complete.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. lid_complete.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. lid_complete.h3d HyperView binary results file. lid_complete.res HyperMesh binary results file. lid_complete.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results Displacement and Stress results are output from OptiStruct for Linear Static Analyses by default. The following steps describe how to view those results in HyperView.

Viewing the Deformed Shape 1. When the message ANALYSIS COMPLETED is received in the HyperWorks Solver View window, click Results. HyperView is launched and the results are loaded. 2. Click the Wireframe Elements icon 3. Set the Animation Mode to Linear

on the toolbar. .

4. Select the Deformed panel toolbar icon 5. Define settings in the Deformed panel.

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a) Set Result type to Displacement (v). b) Set Scale to Model units and enter a value of 2.

This means that the maximum displacement will be two model units and all other displacements will be proportional.

c) Set the toggle under Undeformed Shape to Wireframe. d) Select Color as the Component. 6. Click Apply. A deformed plot of the model should be visible, overlaid on the original undeformed mesh.

Figure 27: Isometric View of Deformed Plot Overlaid on Original Undeformed Mesh with Model Units Set to 2.

Try to answer the following questions to test your understanding of the current problem. • Does the deformed shape look correct for the boundary conditions applied to the mesh?

Viewing a Contour Plot of Stresses and Displacements 1. On the Results toolbar, click

to open the Contour panel.

2. Define settings in the Contour panel. a) Set Result type to Displacement (v). b) Set Data type Mag. Mag represents the magnitude of the displacements. 3. Click Apply. A contoured image of your model should be visible. The contours represent the displacement field resulting from the applied loads and boundary conditions. • What is the maximum displacement value? • At what location does the model have its maximum displacement? • Does this make sense based on the boundary conditions applied to the model? 4. Define settings in the Contour panel.

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a) Set Result type to Element Stresses (2D & 3D). b) Set Data type to vonMises. 5. Click Apply. Each element in the model is assigned a legend color, indicating the von Mises stress value for that element, resulting from the applied loads and boundary conditions. • What is the maximum von Mises stress value? • At what location does the model have its maximum stress? • Does this make sense based on the boundary conditions applied to the model? 6. Click File > Exit to leave HyperView. In this analysis, the region around the hinges may be a concern. There are relatively high stress values that must be resolved. For instance, if testing shows that the coffee pot lid wears out around the hinge area over time, these thermal stresses could possibly cause that fatigue.

Figure 28: Hinge Opposite of the Spout Cut-Out

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OS-T: 1020 Normal Modes Analysis of a Splash Shield In this tutorial, an existing finite element model of an automotive splash shield is used to demonstrate how to set up and perform a normal modes analysis. HyperView post-processing tools are used to determine mode shapes of the model. The sshield.fem file is needed to perform this tutorial.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the sshield.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Reviewing Properties of Rigid Elements There are two rigid "spiders" in the model that are placed at locations where the shield is bolted down. This is a simplified representation of the interaction between the bolts and the shield. It is assumed that the bolts are significantly more rigid in comparison to the shield.

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To be able to distinguish the spiders clearly in the model, you will use the Shaded Elements and Mesh Lines icon

.

The dependent nodes of the rigid elements have all six degrees of freedom constrained. Therefore, each "spider" connects nodes of the shell mesh together in such a way that they do not move with respect to one another. Revert to the Wireframe Elements Skin Only mode by clicking on the

icon.

1. From the menu bar, click Mesh > Edit > 1D Elements > Rigids to open the Rigids panel. 2. Click review. 3. Select one of the rigid elements. In the modeling window, HyperMesh displays the IDs of the rigid element and the two end nodes and indicates the independent node with an 'I' and the dependent node with a 'D'. HyperMesh also indicates the constrained degrees of freedom for the selected element, through the dof check boxes in the Rigids panel. All rigid elements in this model should have all DOFs constrained. 4. Click return to go back to the main menu.

Creating the Material The imported model has four component collectors with no materials. A material collector needs to be created and assigned to the shell component collectors. The rigid elements do not need to be assigned a material. 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter steel.

3. Set Card Image to MAT1. 4. Enter the material values next to the corresponding fields. a) For E (Young's Modulus), enter 2E+05. b) For NU, (Poisson's Ratio), enter 0.3.

c) For RHO (Mass Density), enter 7.85E-009

A material density is required for the normal modes solution sequence.

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Figure 29: Material Property Values for steel

A new material, steel, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Editing the Properties Shell thickness values also need to be corrected. 1. In the Model Browser, Properties folder, click design. The design property entry is displayed in the Entity Editor. 2. For T (thickness), enter 0.25.

3. Change the material assigned to the property from gn to steel. a) For Material, click (1) gn > Material. b) In the Select Material dialog, select steel and click OK. 4. Similarly, on the property nondesign, update T (thickness) to 0.25 and change the material from gn to steel.

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Figure 30: Updating the Thickness Value for Design and Nondesign Property Entries

Applying Loads and Boundary Conditions The model is to be constrained using SPCs at the bolt locations. The constraints are organized into the load collector 'constraints'. To perform a Normal Modes Analysis, a real eigenvalue extraction (EIGRL) card needs to be referenced in the subcase. The real eigenvalue extraction card is defined in HyperMesh as a load collector with an EIGRL card image. This load collector should not contain any other loads.

Creating EIGRL Card In the following steps, the model is constrained so that two opposing edges of the four external edges cannot move. The other two edges remain unconstrained. A total load of 1000N is applied at the edge of the hole in the positive z-direction. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter EIGRL.

3. For Card Image, select EIGRL.

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Figure 31: Selecting the Card Image

4. Click Color and select a color from the color palette. 5. For V2, enter 200.000. 6. For ND, enter 6.

Figure 32: A New Load Collector "EIGRL" is Created in the Model Browser

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

Creating Constraints 1. Create a load collector, named constraints. 2. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 3. With the nodes selector active, select the two nodes at the center of the rigid spiders.

Figure 33: Selecting Nodes for Constraining the Bolt Locations

4. Constrain all DOFs with a value of 0.0. 5. Set load types= to SPC.

6. Click create. Two constraints are created. Constraint symbols (triangles) appear in the modeling window at the selected nodes. The number 123456 is written beside the constraint symbol, if the label constraints is checked "ON", indicating that all DOFs are constrained. 7. Click return.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter bolted.

3. Set Analysis type to Normal modes. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select constraints and click OK. 5. Define METHOD(STRUCT). a) For METHOD(STRUCT), click Unspecified > Loadcol. b) In the Select Loadcol dialog, select EIGRL and click OK.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis An OptiStruct subcase has been created which references the constraints in the load collector constraints and the real eigenvalue extraction data in the load collector EIGRL.

Figure 34: Creating the bolted Loadstep

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 35: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter sshield_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the sshield_complete.fem was written. The sshield_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: sshield_complete.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. sshield_complete.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. sshield_complete.h3d HyperView binary results file. sshield_complete.res HyperMesh binary results file. sshield_complete.stat Summary, providing CPU information for each step during analysis process.

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Viewing the Results Eigenvector results are output by default, from OptiStruct for a Normal Modes Analysis. This section describes how to view the results in HyperView.

Loading the Model and Result Files In this step, you will load a file into the HyperView animation window. 1. When the message ANALYSIS COMPLETED is received in the HyperWorks Solver View window, click Results. HyperView is launched and the results are loaded. 2. Click Close to close the message window, if one appears.

Viewing the Deformed Shape It is helpful to view the deformed shape of a model to determine if the boundary conditions have been defined correctly and also to check if the model is deforming as expected. In this section, use the Deformed panel to review the deformed shape for last mode. 1. Click the animation selector switch in the lower toolbar Mode

and select Set Modal Animation

.

2. Select the Deformed toolbar icon

.

3. Leave Result type set to Eigen mode (v). 4. Set Scale to Model units. 5. Set Type to Uniform and enter in a scale factor of 10 for Value. • This means that the maximum displacement will be 10 modal units and all other displacements will be proportional. • Use a scale factor higher than 1.0 to amplify the deformations while a scale factor smaller than 1.0 would reduce them. In this case, displacements are accentuated in all directions.

Figure 36: Deformed Shape Panel

6. Click Apply. 7. Under Undeformed shape, set Show to Wireframe.

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A deformed plot of the model overlaid on the original undeformed mesh is displayed in the modeling window. 8. In the Results Browser pull-down menu, you can change the view between various subcases using the Load Case and Simulation Selection drop-down menus, as shown below:

Figure 37:

9. Select Mode 6 - F=1.496557E+02 from the list to view Mode 6. 10. To animate the mode shape, click Start/Pause Animation

in the Animation toolbar.

11. To control the animation speed, use the Animation Controls on the Animation toolbar, as shown below:

Figure 38:

12. Review the other mode shapes.

Summary In this analysis, it was assumed that the bolts were significantly stiffer than the shield. If the bolts needed to be made of aluminum and the shield was still made of steel, would the model need to be modified, and the analysis run again? It is necessary to push the natural frequencies of the splash shield above 50 Hz. With the current model, there should be one mode that violates this constraint: Mode 1. Design specifications allow the inner disjointed circular rib to be modified such that no significant mass is added to the part. Is there a configuration for this rib within the above stated constraints that will push the first mode above 50 Hz? See tutorial OS-T: 2020 Increasing Natural Frequencies of an Automotive Splash Shield with Ribs to optimize rib locations for this part.

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OS-T: 1030 3D Inertia Relief Analysis An existing finite element model is used in this tutorial to demonstrate how HyperMesh may be used to set-up an inertia relief analysis. The analysis is then performed using OptiStruct and post-processed in HyperView. The figure below illustrates the structural model used for this tutorial.

Figure 39: Structural Model with Static Loads and Support Constraints Applied

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the ie_carm.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open.

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The ie_carm.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Applying Loads and Boundary Conditions Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter static_loads.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. A new load collector, static_loads is created.

Figure 40: Creating the static_loads Load Collector

5. Create another load collector. a) For Name, enter SPCs.

b) For Card Image, select None.

Creating SUPORT1 Constraint 1. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 2. Create constraint 1. a) Set the entity selector to nodes, then select the node that sits in the middle of the multi-node rigid on the foremost attachment point of the control arm to the chassis. This can be seen in Figure 41 as 1st constraint.

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Figure 41: Nodes to Select for Constraint Boundary Conditions

b) Deselect the degrees of freedom dof4 through dof6 by right-clicking to uncheck each box. c) Set load types = to SUPORT1. The load type is modified to perform inertia relief analysis. d) Click create. 3. Create constraint 2. a) Using the entity selector, select the node and the rearward attachment point of the control arm of the chassis. This can be seen in Figure 41 as 2nd constraint. b) Deselect dof1. c) Click create. 4. Create constraint 3. a) Using the entity selector, select the top node in the rigid which would fasten the bottom of the shock assembly to the control arm. Tip: Switch to the Wireframe Elements Skin Only mode by clicking on the icon to view the rigid.

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b) Deselect dof2. c) Click create.

Figure 42: Final Constraint Applied to Control Arm Model

5. Click return to exit the panel.

Creating Static Forces 1. In the Model Browser, Load Collectors folder, right-click on static_loads and select Make Current to set it as the current load collector. 2. From the menu bar, click BCs > Create > Forces to open the Forces panel. 3. Create force 1. a) Set the entity selector to nodes, then select the node on the top of the rigid at the end of the control arm. This can be seen in Figure 43. b) In the magnitude= field, enter -1e+05. c) Set the direction selector to x-axis. d) Click create. 4. Create force 2. a) Set the entity selector to nodes, then select the node on the top of the rigid at the end of the control arm. This can be seen in Figure 43. b) In the magnitude= field, enter 3e+05.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis c) Set the direction selector to z-axis. d) Click create. 5. Click return and to exit the panel.

Figure 43: Application of Static Forces

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter linear.

3. Set Analysis type to Linear Static. 4. Define LOAD. a) For LOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select static_loads and click OK. 5. Define SUPORT1. a) For SUPORT1, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SPCs and click OK.

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An OptiStruct subcase has been created which references the forces in the load collector static_loads and the inertia relief support points in the load collector SPCs.

Figure 44: Creating the linear Loadstep

Creating Control Cards for Inertia Relief Analysis 1. From the menu bar, click Setup > Create > Control Cards to open the Control Cards panel. 2. Click TITLE and enter a title for this inertia relief analysis, then click return. Tip: Use Next and Prev to browse through the different control card pages. 3. Click PARAM, and enable INREL. 4. Under INREL_V1, toggle the selection to be -1. This requests that an inertia relief analysis be performed. 5. Click return twice to go to the main menu.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 45: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter ie_carm for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the ie_carm.fem was written. The ie_carm.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: ie_carm.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. ie_carm.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. ie_carm.h3d HyperView binary results file. ie_carm.res HyperMesh binary results file.

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ie_carm.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results OptiStruct provides contour information for all of the loadsteps that were run. The following steps describe the process for viewing those results in HyperView.

Viewing the Deformed Shape 1. When the message ANALYSIS COMPLETED is received in the HyperWorks Solver View window, click Results. HyperView is launched and the results are loaded. 2. Verify that the Animate Mode is set to Linear Animation Mode 3. Click the Deformed panel toolbar icon

.

.

4. Set Result Type to Displacement(v). 5. Set Scale to Model units and enter a value of 10.

This means that the maximum displacement will be 10 model units and all other displacements will be proportional.

6. Click Apply. 7. Set the toggle under Undeformed shape to Wireframe and select Color as the Component. A deformed plot of the model should be visible, overlaid on the original undeformed mesh.

Viewing Deformed Animation of Loading Displacement 1. Verify that the Animate Mode is set to Linear Animation Mode 2. Click the Start/Pause Animation icon

.

to start the animation.

Note: Both the play speed and starting point of the animation can be controlled using the Animation Controls. 3. With the animation running, use the lower slider bar in the Animation Controls panel to adjust the speed of the animation.

Figure 46:

4. Click the Start/Pause Animation icon, again, to stop the animation.

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Viewing a von Mises Stress Contour 1. On the Results toolbar, click

to open the Contour panel.

2. Select Element Stresses (2D & 3D) as the Result type. 3. Verify that the stress type is set to vonMises. 4. Click Apply. Notice the graphical display of stresses 5. Once you are finished viewing, select File > Exit to exit HyperView. Note: Beginning with 8.0, there is a parameter PARAM, INREL, -2 that can activate inertia relief analysis without the need for a SUPORT/SUPORT1 entry. You can activate that parameter by clicking on the PARAM field on the Control Cards panel. In this tutorial, our intention was to show the steps in creating SUPORT1 cards; therefore the parameter was not used. As an additional exercise, you could run this tutorial using the above mentioned parameter. In that case, you would not create SUPORT1 cards or choose that load collector in the subcase.

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OS-T: 1040 3D Buckling Analysis In this tutorial the steps required to perform a buckling analysis using OptiStruct are covered. The figure below illustrates the structural model used for this tutorial.

Figure 47: Structural Model with Static Loads and Constraints Applied

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the buckling.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The buckling.fem database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Applying Loads and Boundary Conditions Creating Load Collectors Create three load collectors (SPC, Static load and Buckling load). 1. Create the SPC load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter SPC.

c) Click Color and select a color from the color palette.

Figure 48: SPC Load Collector

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2. Create another load collector named Static load. 3. Create another load collector named Buckling load. a) For Card Image, select EIGRL. b) For V1, enter 0.0. c) For ND, enter 2.

This tells OptiStruct that you would like to extract the first two buckling modes.

Creating Loads and Boundary Conditions 1. In the Model Browser, Load Collector folder, right-click on SPC and select Make Current from the context menu.

Figure 49:

2. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 3. Select all of the nodes on the bottom face of the beam. a) Click nodes > on plane. b) Verify that the N1 selector is active, then click any three nodes on the plane. c) Click select entities. All of the nodes on the plane are selected.

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Figure 50:

4. Deselect the degrees of freedom dof4 through dof6. 5. Click create to create the necessary boundary constraints. 6. Click return. 7. In the Model Browser, Load Collector folder, right-click on Static load and select Make Current from the context menu. 8. From the menu bar, clickBCs > Create > Forces to open the Forces panel. 9. Select all of the nodes on the top face of the beam.

Figure 51: Nodes Selected for Application of Static Forces

10. In the magnitude= field, enter -10000. 11. Set the direction selector to z-axis.

12. Click create. The forces display in the modeling window. 13. Click return.

Creating a Load Step The last step in establishing boundary conditions is the creation of a subcase.

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1. Create the Linear load step. a) In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. b) For Name, enter Linear.

c) Set Analysis type to Linear Static. d) For SPC, click Unspecified > Loadcol. e) In the Select Loadcol dialog, select SPC and click OK. f) For LOAD, click Unspecified > Loadcol. g) In the Select Loadcol dialog, select Static load and click OK.

Figure 52:

2. Create the Buckling load step. a) In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. b) For Name, enter Buckling.

c) Set Analysis type to Linear buckling. d) For METHOD(STRUCT), click Unspecified > Loadcol. e) In the Select Loadcol dialog, select Buckling load and click OK.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis f) For STATSUB(BUCKLING), click Unspecified > Loadcol. A STATSUB card allows for the selection of a linear static subcase for buckling analysis. g) In the Select Loadcol dialog, select Linear and click OK.

Figure 53:

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 54: Accessing the OptiStruct Panel

2. Click save as.

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3. In the Save As dialog, specify location to write the OptiStruct model file and enter buckling for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the buckling.fem was written. The buckling.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: buckling.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. buckling.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. buckling.h3d HyperView binary results file. buckling.res HyperMesh binary results file. buckling.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results OptiStruct gives you contour information for all of the loadsteps that were run. This section describes the process for viewing those results in HyperView.

Viewing Linear Load Step Results 1. From the OptiStruct panel, click the HyperView icon. HyperView launches with the buckling.fem file which contains the model and the results.

2. Use the drop-down Subcase selector to change the analysis that you are reviewing in the current window.

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Figure 55:

3. In the Results Browser, select Subcase 1 - Linear. 4. On the Results toolbar, click

to open the Contour panel.

5. Select Element Stresses (2D and 3D) as the Result type and set the sub type to von Mises. 6. Click Apply. This should show the contour of von Mises stress.

Viewing Buckling Load Step Results 1. Click Clear Contour from the Result display control panel. 2. In the Results Browser, click Subcase 2 - Buckling and make sure the simulation is for Mode 1. 3. Click the Deformed panel toolbar

.

4. Under Deformed shape, enter a value of 10.

5. Under Undeformed shape, for Show, select Wireframe from the drop-down list.

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Figure 56:

6. Click the Start/Pause Animation icon

to view the animation.

7. Similarly, check the results for the 2nd mode.

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OS-T: 1050 Connection of Dissimilar Meshes using CWELD Elements In this tutorial, an existing finite element model of a simple cantilever beam is used to demonstrate how to connect dissimilar meshes using CWELD elements.

Figure 57: Cantilever Beam with Dissimilar Meshes

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh.

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The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the dissimilar.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The dissimilar.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Properties The database contains two unconnected components: solid_fine and solid_coarse. These unconnected components are to be connected by CWELD elements using the grid to element option. In order to achieve this, membrane elements need to be created on the matching faces of the solid_coarse and solid_fine components. 1. In the Model Browser, right-click and select Create > Property. A default PSHELL property template displays in the Entity Editor. 2. For Name, enter membrane_coarse.

3. For Card Image, select PSHELL from the drop-down menu. 4. For Material, click Unspecified > Material. 5. In the Select Material dialog, select steel and click OK. 6. Check the box next to MID2_opts. An option list appears beneath MID2_opts. 7. Click the switch next to USER and select BLANK from the pop-up menu. Notice the MID2 field disappears from the card image.

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Figure 58:

8. Check the box next to MID3_opts. An option list appears beneath MID3_opts. 9. Click the switch next to USER and select BLANK from the pop-up menu. 10. Notice the MID3 field disappears from the card image. 11. For T (thickness), enter 1E-6.

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Figure 59:

12. In the Model Browser, right-click and select Create > Property. A default PSHELL property template displays in the Entity Editor. 13. For Name, enter membrane_fine.

14. Input the corresponding values for membrane_fine exactly the same as for membrane_coarse. 15. In the Model Browser, right-click and select Create > Component. 16. For Name, enter membrane_coarse.

17. For Property, click Unspecified > Property. 18. In the Select Property dialog, select membrane_coarse and click OK.

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Figure 60:

19. From the Tool page, click faces. 20. Click comps, select the solid_coarse component, click select > find faces. Membrane elements are created on the faces of solid_coarse component and they appear on the modeling window. 21. In the Model Browser, right-click the component ^faces and click Isolate. This displays only ^faces component. 22. From the Tool page, click organize. 23. Select only the elements that lie on the matching face. (Rotate the model so you can see the matching face, then, after making sure elems is selected, click on any one of the elements on the matching face. Then, click elems >> by face. This selects all the elements on the matching face).

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Figure 61: Selecting Elements on Matching Face for solid_coarse Component

24. Click dest component = and select membrane_coarse from the list of components. 25. Click move. The elements are now part of the membrane_coarse component. 26. Click return. 27. On the Tool page, select faces. 28. Click delete faces. 29. Click return to exit the panel. 30. In the Model Browser, right-click and select Create > Component. 31. For Name, enter membrane_fine.

32. For Property, click Unspecified > Property. 33. In the Select Property dialog, select membrane_fine and click OK. 34. On the Tool page, select faces. 35. Click comps, select the solid_fine component, and click select > find faces. Membrane elements are created on the faces of solid_fine component and they appear on the modeling window. 36. Click return. 37. Right-click ^faces component and click Isolate. This displays only ^faces component in the modeling window. 38. From the Tool page, select the organize panel. 39. Select only the elements that lie on the matching face as shown below. (Use a method similar to the one mentioned in Step 23).

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Figure 62: Selecting Elements on Matching Face for Solid Fine Component

40. Click dest component= and select membrane_fine from the list of components. 41. Click move. The elements are now part of the membrane_fine component. 42. Click return. 43. From the Tool page, select the faces panel. 44. Click delete faces and click return to return to the main menu. 45. In the Model Browser, right-click and select Components > Hide. 46. Click the icon highlighted in red below to keep only the membrane elements in display.

Figure 63: Displaying Only Membrane Elements

Creating CWELD Elements A PWELD property must be created for the CWELD elements. 1. In the Model Browser, right-click and select Create > Property. A default PSHELL property template displays in the Entity Editor. 2. For Name, enter welds.

3. For Card Image, select PWELD from the drop-down menu and click Yes to confirm.

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4. For Material, click Unspecified > Material. 5. In the Select Material dialog, select steel and click OK. 6. For D (weld diameter), enter 0.1. This creates a new property definition named welds. 7. In the Model Browser, right-click and select Create > Component. 8. For Name, enter welds. 9. Click Color and select a color. This creates the new component named welds. 10. From the 1D page, click spotweld. 11. Make sure the using elems subpanel is selected. 12. Click elems >> displayed. 13. Click the switch under element config and select rod from the pop-up menu. 14. Click property = and select welds from the list of properties. 15. Click search tolerance = and enter 0.1.

16. Click nodes >> by collector and select the membrane_fine collector. 17. Click create. A weld element is created at each node on the fine-mesh matching face. A number of plot elements are created too, these are helpful to find the elements attached when looking for the welds. 18. Click return to go back to the main menu.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 64: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter dissimilar for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the dissimilar.fem was written. The dissimilar.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: dissimilar.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. dissimilar.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. dissimilar.h3d HyperView binary results file. dissimilar.res HyperMesh binary results file. dissimilar.stat Summary, providing CPU information for each step during analysis process.

Post-processing the Results Viewing Displacement Contour 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Set the animation type to Linear 3. On the Results toolbar, click

.

to open the Contour panel.

4. Select the first pull-down menu below Result type: and select Displacement (v). 5. Click Apply. The resulting colors represent the displacement field resulting from the applied loads and boundary conditions.

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on the toolbar.

7. Choose the second layout in the first row of the pop-up window. This changes the modeling window in two separate windows. The left window will have the previously loaded model and the right window will be blank. 8. Load the control example in the right side window to compare the results. 9. Click the right-hand pane in the display area. A blue line appears around the window to show that it is selected. 10. Click the Load Result icon 11. Click Load Model

in the toolbar.

and select the file control.h3d you saved to your working directory from

the optistruct.zip file as both the model and results file.

12. Click Apply.

13. Right-click on the left pane and activate menu over Apply Style To > Current Page > All Selected. This option applies results from the current window to the new window. You can now visually compare the displacement results from the dissimilar mesh model with a uniform mesh model.

Viewing the Results 1. Select the left-hand panel in the display area. 2. On the Results toolbar, click

to open the Contour panel.

3. Under Result type, select Element Stresses (2D & 3D)(t) and vonMises. 4. In the field below Averaging method, select None. 5. Click Apply. 6. Right-click on the left pane and activate menu over Apply Style To > Current Page > All Selected. You can now visually compare the von Mises stress results from the dissimilar model with a uniform mesh model.

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OS-T: 1060 Analysis of a Composite Aircraft Structure using PCOMPG This tutorial takes you through the process of developing a ply lay-up definition for a composite structure using a PCOMPG card, and shows the advantages of post-processing the results with global ply numbers. The traditional definition method, using PCOMP, is introduced first here to ultimately show the practical advantages of using PCOMPG for the given scenario. The model for this tutorial is shown below. Since the structure, loads, and boundary conditions are symmetrical about the x-axis, only one half of the structure is modeled with suitable boundary conditions applied to enforce half symmetry.

Figure 65: Torsion Frame

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the frame.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The frame.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Reviewing the Model Setup The structural model has been already set up and can be solved without any further modifications. Review the model setup before submitting the job. The model is set up for Linear Static Analysis. As mentioned earlier, only half of the structure is modeled; and to impose the half symmetry boundary conditions, all the nodes on the symmetry plane are constrained in DOF1, DOF5, and DOF6. All of the components are modeled with the PCOMP property which lists the plies (stacking sequence) from the bottom surface upwards, with respect to the element's normal direction, as shown in Figure 66.

Figure 66: Ply Stacking Sequence with Respect to Element Normal

Components in this model that have names starting with the word "Flange" represent junctions in which different components are connected together. While reviewing, closely watch the flange area formed by the Skin and Rib components (highlighted in the following figure). Review the ply lay-up of the Skin_inner, Rib, Flange1_Rib_Skin, and Flange2_Rib_Skin components (laminate layout is shown in the bottom portion of the following figure). Note: Few plies are common for the Skin_inner, Flange1_Rib_Skin, Flange2_Rib_Skin, and Skin_outer components, but appear in different stacking sequence in each component. For example, the 4th ply in Skin_inner is the 3rd ply in Flange2_Rib_Skin and the 2nd ply in the Skin_outer components.

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Figure 67: Ply stacking for the Skin_inner, Rib, Skin_outer, Flange1_Rib_Skin, and Flange2_Rib_Skin Components

1. From the 2D page, click HyperLaminate. This opens the HyperLaminate GUI, in which the ply lay-up information can be defined, reviewed and edited. Material properties and design variables can also be created and edited here. 2. Expand the Laminates portion of the tree structure on the left-hand side of the screen. 3. Select the Skin_inner PCOMP. Details of the laminate appear in the GUI. 4. Verify that the lay-up definition for Skin_inner matches the first 5 entries of the table below, which is the lay-up information of Flange1_Rib_Skin component. 5. Select the Rib PCOMP and verify that the 3rd and 4th lay-up definition for Rib matches the 6th and 7th entries in the following table. 6. Select the Flange1_Rib_Skin PCOMP to view the ply lay-up definitions. Verify that the lay-up definition for Flange1_Rib_Skin matches the following table. Notice that the first 5 layers are the same as Skin_inner lay-ups and that the last two lay-ups are the same as the 3rd and 4th lay-up of Rib, as shown in the last figure. You can verify how other flanges are modeled. Table 1: Laminate properties of Flange1_Rib_Skin

Ply Number

Material

Thickness T

Orientation

SOUT

1

carbon_fiber

1.2

45

YES

2

matrix

0.2

90

YES

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Ply Number

Material

Thickness T

Orientation

SOUT

3

carbon_fiber

1.2

-45

YES

4

matrix

0.2

-90

YES

5

carbon_fiber

1.2

90

YES

6

matrix

0.2

-45

YES

7

carbon_fiber

1.2

45

YES

7. You can also review the other components. Once the review is completed, select File > Exit to exit the HyperLaminate GUI and return to HyperMesh.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 68: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter frame_PCOMP for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job.

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If the job is successful, new results files should be in the directory where the frame_PCOMP.fem was written. The frame_PCOMP.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: frame_PCOMP.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. frame_PCOMP.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. frame_PCOMP.h3d HyperView binary results file. frame_PCOMP.res HyperMesh binary results file. frame_PCOMP.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results/Post-processing 1. Click HyperView from the OptiStruct panel. HyperView launches and the model results are automatically loaded. 2. Click Close to close the message window. 3. Click the Contour toolbar

.

4. Select the first switch below Result type and select Composite Stresses(s). 5. Select the second switch and select the P1 (major) Stress. 6. Select 3 for the Layers option. 7. In the field below Averaging method, select None.

Figure 69:

8. Click Apply.

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This contours the maximum principle stress for the 3rd ply of all the components in the model. 9. Click the Isometric View icon

in the Standard Views toolbar to see the model, as shown in

the following figure.

Figure 70: Stress Distribution on the Top Face of the Frame

The stress value does not vary gradually in the top face region, but suddenly decreases to a lower value across the Flange2_Rib_Skin component. Looking at the table of laminate properties of Flange1_Rib_Skin again, observe that the 3rd ply property of the Flange2_Rib_Skin component is of a matrix material and the third plies in the components adjacent to it (Flange1_Rib_Skin and Skin_outer) are of a carbon fiber material. The sudden changes in the stress values occur because we are looking at stress on two different materials. This example shows that, for the results to be meaningful during post-processing of the PCOMP results, you have to correlate the ply results to their corresponding ply property. This highlights that, during the post-processing of PCOMP components, plotting results based on just the ply number is not sufficient. You have to keep track of ply properties (material, thickness, orientation, failure index, etc.) on your own during post-processing with this method. In cases that use large and complex models, it becomes tedious to track the individual ply properties during postprocessing. This drawback to using PCOMP can be avoided with the use of the PCOMPG card for property definition. Using the PCOMPG card, you can assign a global ply number for each ply and post-process the results based on global ply number. The following steps explain the procedure to redefine the model with PCOMPG property.

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Redefining the Model Setup 1. Close the HyperView window and return to HyperMesh. Tip: Click

to return to the previous page where HyperMesh is open, if you are

using HyperMesh Desktop. 2. From the 2D page, select the HyperLaminate panel. This opens the HyperLaminate GUI in which the ply lay-up information can be defined, reviewed and edited. 3. Click Tools > Laminate Options. This opens a new window in which the default ply lay-up options can be set. 4. Click the Convention switch and select Total. 5. Click OK to close the window. This sets up Total as the default option whenever a new component is created.

Figure 71: Laminate Information with Global Ply Number

Now you create new PCOMPG components with global ply numbers defined as shown in Figure 71. As discussed earlier, the 4th ply in Skin_inner is the 3rd ply in Flange2_Rib_Skin and the 2nd ply in Skin_outer components. Therefore, all of these plies will be defined with the same global ply ID 4. Similarly, all other plies are to be defined, as shown in Figure 71. 6. Expand the laminates portion of the tree structure on the left-hand side of the screen. 7. Right-click PCOMPG. A menu appears. 8. Click New. This creates new component, which is named NewLaminate1 by default, and the tree structure is expanded. 9. Rename the component to Skin_inner_GPLY by right-clicking and select Rename in the text field and overwrite the default component name. 10. In the Add/Update plies section, under the field GPLYID, enter 1.

11. Select the pull-down menu below Material and select carbon_fiber. 12. Below the Thickness T1 field, enter 1.2. 13. Below the Orientation field, enter 45.

14. Select the pull-down menu below SOUT and select YES.

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15. Click Add New Ply to add the ply information. 16. Repeat this procedure to add 4 more plies with the properties shown in the table: GPLYID

Material

Thickness T

Orientation

SOUT

2

matrix

0.2

90

YES

3

carbon_fiber

1.2

-45

YES

4

matrix

0.2

-90

YES

5

carbon_fiber

1.2

90

YES

17. Click Update Laminate at the bottom of the window to update the lay-up information. The graphical display of lay-up information now appears in the field below the Review tab, on the right side of the GUI. 18. Create a new PCOMPG component with name Rib_GPLY and the ply lay-up, as shown in the following table: GPLYID

Material

Thickness T

Orientation

SOUT

11

carbon_fiber

1.2

0

YES

12

matrix

0.2

45

YES

13

matrix

0.2

-45

YES

14

carbon_fiber

1.2

45

YES

Refer to Figure 71 to create the Flange1_Rib_Skin_GPLY component. 19. Right-click Skin_inner_GPLY and select Duplicate from the menu to create an identical component. 20. Rename the component as Flange1_Rib_Skin_GPLY by right-clicking and selecting rename.

21. Add 2 more plies with the properties shown in the following table using the Add New Ply feature. GPLYID

Material

Thickness T

Orientation

SOUT

13

matrix

0.2

-45

YES

14

carbon_fiber

1.2

45

YES

The new component Flange1_Rib_Skin_GPLY was created. Its first 5 plies are the same as Skin_inner_GPLY and its last 2 plies are the 3rd and 4th plies of the Rib component.

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To reduce the number of steps in this tutorial, the ply lay-up information of other components is already defined with PCOMPG property and appropriate laminate information in the updated_PCOMPG_properties.fem file you saved to your working directory from the optistruct.zip file. This file is imported into HyperMeshto update (overwrite) the properties instead of manually updating them. The updated_PCOMPG_properties.fem file is saved in OptiStruct input file format. Open this in any text editor to review how the components are defined with PCOMPG properties. A section of the file is shown below.

Figure 72: Components defined with PCOMPG

22. Click File > Exit to exit the HyperLaminate GUI and return to HyperMesh. 23. Click File > Import > Solver Deck. 24. Click the toggle to expand the Import options and check the box next to FE overwrite. This option overwrites the old PCOMP properties with PCOMPG properties defined in the updated_PCOMPG_properties.fem file. 25. Click on the folder icon Import.

next to File, select the updated_PCOMPG_properties.fem file and click

26. Click Close.

Reviewing the Imported Properties in HyperLaminate 1. From the 2D page, go to the HyperLaminate panel. 2. Expand the laminates portion of the tree structure on the left-hand side of the screen. All of the components now appear under PCOMPG. The components created earlier (Skin_inner_GPLY, Rib_GPLY, and Flange1_Rib_Skin_GPLY) are still present. There is no element associated with these components. Review the PCOMPG components to view the laminate definitions. 3. Click File > Exit.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 73: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter frame_PCOMPG for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the frame_PCOMPG.fem was written. The frame_PCOMPG.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: frame_PCOMPG.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. frame_PCOMPG.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. frame_PCOMPG.h3d HyperView binary results file. frame_PCOMPG.res HyperMesh binary results file.

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frame_PCOMPG.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results/Post-processing 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. On the Results toolbar, click

to open the Contour panel.

4. Select the first switch below Result type and select Composite Stresses (s). 5. Select the second switch and select P1 (major) Stress. 6. For the Layers field, select PLY 3. 7. For Averaging method, select None. 8. Click Apply. This plots the maximum principle stress for global ply 3. The results are not plotted in the regions where global ply 3 is not present. 9. Click the Isometric View icon

in the Standard Views toolbar.

Figure 74:

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Post-processing the results based on global ply number eliminates the need to track the ply number and corresponding ply properties on the components. The results are displayed based on the global ply number, irrespective of the ply order, so you can chose any one global ply number and view results across the whole component. If a particular ply is not present in any given region, no result is displayed.

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OS-T: 1070 Analysis of an Axi-symmetric Structure In this tutorial the method of modeling an axi-symmetry problem in OptiStruct is covered. The figure below shows the model that is used for this tutorial.

Figure 75: Full Model; Elements, Material, Props and BCs

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the axi-symmetry_full_geometry.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The axi-symmetry_full_geometry.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Exercise 1: Analysis with the Full Model You will find that the structural model has already been set up with the necessary elements, boundary conditions, property, and material data so that it is ready to solve. Pressure load is applied on the top face of the geometry and constraints are defined at the bottom face. Note that the model is symmetrical about the z-axis and that loads and boundary conditions are symmetrical about the same axis as well. These represent the conditions necessary for modeling axi-symmetry problems. First, obtain the result for the full model and then you model a small part of the model with boundary conditions suitable to enforce the axi-symmetric behavior. Finally, you compare the results of the axisymmetric model with the full model results.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 76: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter axisymmetry_full_geometry for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job.

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If the job is successful, new results files should be in the directory where the axisymmetry_full_geometry.fem was written. The axi-symmetry_full_geometry.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. Displacement and stress results are output for each subcase to the axi-symmetry_full_geometry.h3d file from OptiStruct. This section describes how to view those results in HyperView.

Viewing the Displacements of the Structure It is helpful to view the deformations of the model first, to determine if the boundary conditions have been defined correctly and also to see if the model is deforming as expected. 1. Set the Animation mode to Linear. 2. On the Results toolbar, click

to open the Contour panel.

3. Select the first pull-down menu below Result Type and select Displacement [v]. 4. Select the second pull-down menu below Result Type and select Mag.

Figure 77:

5. Click Apply to display the displacement contour. Tip: To view the displacement variation across the thickness, one half of the structure can be masked. 6. Expand the Components folder in the Results Browser. 7. Click the elements icon in front of the component bottom_half to mask the component from display.

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Figure 78:

8. Click XZ Left Plane View

to display the Left view.

The following figure shows the displacements through the thickness.

Figure 79:

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Exercise 2: Analysis with a Small Portion of the Full Model with Axi-symmetry Boundary Conditions Setting up the New Analysis Return to HyperMesh to delete the all the elements, except for a small portion and to set up the axisymmetry boundary conditions. Before proceeding to the next section, look at the criteria for modeling an axi-symmetry problem. Even if the geometry is symmetrical about an axis, if any of the loads or boundary conditions are not symmetrical about the same axis, then it cannot be modeled as an axi-symmetry model. Therefore, the models shown below are examples that cannot be modeled as axi-symmetry models.

Figure 80: Left: Non Axi-symmetric Loads; Right: Non Axi-symmetric Boundary Conditions

Setting up the Axi-symmetry Model 1. Click

to enter the Delete panel, or click F2.

2. Make sure the entity selection switch is set to elems. 3. Click the yellow button elems to open the extended entity selection window and select by sets. 4. Click in the check box in front of SetA. A check mark appears before SetA to indicate that it is selected. 5. Click select. The selected elements are highlighted. 6. Click delete entity to delete the selected elements.

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7. Click return to exit the Delete panel. Use the retained portion to model the axi-symmetric model with suitable boundary conditions.

Applying the Additional Boundary Conditions The axi-symmetry conditions are applied by constraining all of the nodes from moving in the tangential direction. This is done by first assigning all of the nodes to a cylindrical coordinate system and then constraining all of them in tangential degrees of freedom. 1. From the Analysis page, enter the Systems panel. 2. Select the assign radio button. 3. Make sure the entity selection switch in front of set: is set to nodes. 4. Click the yellow button nodes to open the extended entity selection window and select all. 5. Click the yellow button system to activate it and select the red colored system from the modeling window. 6. Click set displacement. The message on the footer bar The analysis system has been assigned appears. 7. Click return.

All of the nodes in the model are assigned to a cylindrical coordinate system. The z-axis of the cylindrical coordinate system coincides with the axis about which the model is symmetrical. Now, constraining the nodes that are assigned to the cylindrical coordinate system in tangential degrees of freedom enforces the axi-symmetry boundary condition.

Creating Constraints 1. Expand the Load Collectors folder in the Model Browser. 2. Right-click on SPCs and click Make Current to make SPCs the current component, if not already done. 3. Click BCs > Create > Constraints to open the Constraints panel. 4. Make sure the entity selection switch is set to nodes. 5. Click the yellow button nodes to open the extended entity selection window and select all. 6. Constrain dof2. • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 7. Click create. This applies these constraints to the selected nodes. 8. Click return to go back to the main menu. Next you will submit the job, as was complete in Exercise 1. 9. From the Analysis page, enter the OptiStruct panel.

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10. Solve the job with file name as axi-symmetry_model.fem by following the same steps as explained in the earlier section. If the job is successful, new results files can be seen in the directory where the OptiStruct model file was written. The axi-symmetry_model.out file is a good place to look for error messages that will help to debug the input deck if any errors are present.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 81: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter axisymmetry_model for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the axi-symmetry_model.fem was written. The axi-symmetry_model.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Displacement and Stress results are output for each subcase to axi-symmetry_model.h3d file from OptiStruct. Results from the axi-symmetry model should match with the results of the full model. Use load the result file in the previously opened HyperViewsession to compare the results. 1. Click HyperView to view the results.

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. .

4. Activate the new window by clicking in the modeling window of the new window. 5. Click

to open the Load Model and Results panel.

6. Click the Load model icon

on the toolbar and load the axi-symmetry_model.h3d.

This loads the complete path of the selected .h3d file in the field. Also, note that the same file path is loaded next to the field Load results. 7. Click Apply. 8. Click XZ Left Plane View 9. Click the Contour icon

to display the Left view. on the toolbar and contour the displacements.

10. Compare the displacement results of the axi-symmetry model with the result from the full model. The results should match, as shown in the below picture. Similarly, stress and other results will also match.

Figure 82: Comparison of Displacement Results

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OS-T: 1080 Coupled Linear Heat Transfer/Structure Analysis A coupled heat transfer/structure analysis on a steel pipe is performed in this tutorial. As shown in the figure below, the pipe is fixed on the ground at one end and the heat flux is applied on the other end. A linear steady-state heat conduction solution is defined first. Then it is referred by a structure solution by TEMP to perform the coupled thermal/structural analysis. The problem is defined in HyperMesh and solved with OptiStruct implicit solver. The heat transfer and structure results are post processed in HyperView.

Figure 83: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon

.

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A Select OptiStruct file browser opens. 4. Select the pipe.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating Coupled Thermal/Structural Material and Property Create the material and property collectors before creating the component collectors. 1. In the Model Browser, right-click and select Create > Material. A default MAT1 material displays in the Entity Editor. 2. For Name, enter steel.

3. Click the box next to MAT4. The MAT4 card image appears below MAT1 in the material information area. The MAT1 card defines the isotropic structural material. MAT4 card is for the constant thermal material. MAT4 uses the same material ID as MAT1. If a quantity in brackets does not have a value below it, it is turned OFF. 4. To add a value, click the quantity in brackets. An entry field appears below it. 5. Click the entry field and enter a value. 6. Enter the following values for the material, steel, in the Entity Editor. 11

[E] Young's modulus

2.1 x 10

[NU] Poisson's ratio

0.3

[RHO] Material density

7.9 x 10 Kg/m

[A] Thermal expansion coefficient

1 x 10 / °C

[K] Thermal conductivity

73W / (m * °C)

Pa

3

3

-5

A new coupled thermal/structural material, steel, is created.

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Figure 84: The Material Entity Editor

7. In the Model Browser, right-click and select Create > Property. A default PSHELL property displays in the Entity Editor. 8. For Name, enter solid.

9. For Material, click Unspecified > Material. 10. In the Select Material dialog, select steel and click OK.

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Figure 85: Assigning the Material steel to the Property solid

11. For Card Image, select PSOLID from the drop-down menu and click Yes to confirm. The property of the solid steel pipe has been created as 3D PSOLID. Material information is linked to this property.

Linking Material and Property to Existing Structure Once the material and property are defined, they need to be linked to the structure. 1. In the Model Browser, click on the pipe component. The component template displays in the Entity Editor. 2. For Property, click Unspecified > Property. 3. In the Select Property dialog, select solid and click OK.

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Figure 86: Assigning the Property solid to the Component pipe

Applying Thermal Loads and Boundary Conditions to the Model A structural constraint spc_struct is applied on the RBE2 element to fix the pipe on the ground. Two empty load collectors, spc_heat and heat_flux have been pre-created. In this section, the thermal boundary conditions and heat flux are applied on the model and saved in spc_heat and heat_flux, respectively.

Creating Thermal Constraints 1. Click the Set Current Load Collector panel located at the right corner of the footer bar, as shown below. A list of load collectors appears.

Figure 87: Setting the Current Load Collector

2. Select spc_heat as the current load collector. 3. From the Analysis page, click constraints. 4. Go to the create subpanel.

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5. Click the entity selection switch and select nodes from the pop-up menu. 6. Click nodes >> by sets. 7. Select the predefined entity set heat and click select. The selected nodes on the fixed end should be highlighted. 8. Uncheck the boxes in front of dof1, dof2, dof3, dof4, dof5, and dof6 and enter 0.0 in the entry fields. 9. Click load types = and select SPC from the pop-up list. 10. Click create. This applies these thermal constraints to the selected nodal set. 11. Click return to go to the Analysis page.

Creating CHBDYE Surface Elements The heat flux will be applied on the surface of the free end of the pipe. Therefore, the surface elements CHBDYE for defining heat transfer boundaries must be created first. 1. Click BCs > Create > Interfaces. 2. For Name, enter heat_surf.

3. For Card Image, select CONDUCTION from the drop-down menu. 4. Select an appropriate color from the palette. 5. For Slave Entity IDs, click Elements. The Slave Entity IDs panel is now displayed below the Graphics browser. 6. Click the switch button for elems and select faces from the pop-up list. 7. Click the highlighted solid elems and select by sets from the pop-up selection menu. 8. Select element set solid elems and click select. 9. Click nodes in the face nodes field. 10. Select four nodes on one face of a solid element where the heat flux is applied, as shown in Figure 88.

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Figure 88: Nodes on the Surface Element

11. Click add. This adds the CHBDYE surface elements on all the solid elements following the same side convention, as shown in Figure 89.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis

Figure 89: CHBDYE Surface Elements

12. Click return to return to the Entity Editor. 13. Click Close.

Creating Heat Flux on Surface Elements In this step, the uniform heat flux into CHBDYE elements is defined with QBDY1 entries. 1. Set your current load collector to heat_flux. 2. From the Analysis page, click flux to enter the Flux panel. 3. Go to the create subpanel. 4. Click elems >> by group. 5. Select heat_surf and click select. The surface elements are highlighted. 6. Click load types= and select QBDY1. 7. In the value= field, enter 1.0.

8. Click create. The uniform heat flux in the surface elements is defined. 9. Click return to go back to Analysis page.

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Creating Heat Transfer Load Step An OptiStruct steady state heat conduction loadstep is created, which references the thermal boundary conditions in the load collector spc_heat and the heat flux in the load collector heat_flux. The gradient, flux, and temperature output for the heat transfer analysis are also requested in the load step. 1. In the Model Browser, right-click and select Create > Load Step. A default load step displays in the Entity Editor. 2. For Name, enter heat_transfer.

3. Click the drop-down menu in the Value field next to Analysis type in the Entity Editor and select Heat transfer (steady state). 4. For SPC, click Unspecified > Loadcol. 5. In the Select Loadcol dialog, select spc_heat and click OK.

Figure 90: Selecting the Constraints

6. For LOAD, click Unspecified > Loadcol. 7. In the Select Loadcol dialog, select heat_flux and click OK. 8. Verify that the Analysis type is set to HEAT. 9. Check the box next to OUTPUT. 10. Activate the options of FLUX and THERMAL on the sub-list. 11. Under each result selection, click the space next to FORMAT and select H3D format from the dropdown menu. For THERMAL, click the Table icon

and select H3D from the drop-down menu in

the table that opens. 12. Click the button under OPTION and select ALL, as shown in Figure 91. Flux and Thermal output can also be requested in the Control Cards panel on the Analysis page.

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Figure 91: Setting up the Heat Transfer Loadstep

Creating a Structure Load Step To perform a coupled thermal/structural analysis, the heat transfer SUBCASE needs to be referenced by a structural SUBCASE through TEMP card. Since this is not directly supported in HyperMesh, a linear static structural subcase is created and temperature is added using SUBCASE_UNSUPPORTED or by editing the .fem file after the model export. 1. In the Model Browser, right-click and select Create > Load Step. A default load step displays in the Entity Editor. 2. For Name, enter structure_temp.

3. Click on the drop-down menu in the Value field next to Analysis type in the Entity Editor and select Linear Static. 4. For SPC, click Unspecified > Loadcol. 5. In the Select Loadcol dialog, select spc_struct and click OK. 6. Check the box next to SUBCASE_UNSUPPORTED. 7. Click the Table icon

to the right of Data: Comments and enter the following text in the first

row of the pop-out table. TEMP=1 Note the TEMP ID used above could be different from your model. Make sure the ID of the heat transfer subcase is selected for TEMP. 8. Click Close.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 92: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter pipe_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the pipe_complete.fem was written. The pipe_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Gradient temperatures and flux contour results for the steady state heat conduction analysis and the stress and displacement results for the structural analysis are computed from OptiStruct. HyperView is used to post-process the results.

Viewing Heat Transfer Analysis Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears.

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to open the Contour panel.

4. Select Subcase 1 - heat transfer as the current load case in the Results tab, as shown below.

Figure 93: Results tab in HyperView

5. In the Contour panel, select the first pull-down menu below Result type and select Element Fluxes (V). 6. Click Apply. A contoured image representing thermal fluxes should be visible. 7. Select the first pull-down menu below Result type and select Grid Temperatures (s). 8. Click Apply. Both flux and temperature results are shown below.

Figure 94: Results of Heat Transfer Analysis

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Viewing the Results for the Coupled Thermal/Structure Analysis 1. Select the structure analysis subcase as the current load case in the Load Case and Simulation Selection window. 2. Select the first pull-down menu below Result type and select Element Stresses [2D & 3D] (t). 3. Select the second pull-down menu below Result type and select vonMises. 4. Click Apply. A contoured image representing von Mises stresses should be visible. Each element in the model is assigned a legend color, indicating the von Mises stress value for that element, resulting from the applied loads and boundary conditions. 5. Select the first pull-down menu below Result type and select Displacement (v). 6. Select the second pull-down menu below Result type and select Mag. 7. Click Apply. Both stress and displacement contours are shown below.

Figure 95: Results of the structural analysis

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OS-T: 1085 Linear Steady-state Heat Convection Analysis This tutorial performs a heat transfer analysis on a steel pipe. The temperature on the inside surface of the pipe is 60°C. The outside surface is exposed to the surrounding air, which is at 20°C. The temperature distribution within the pipe can be determined by solving the linear steady state heat conduction and convection solution.

Figure 96: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

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4. Select the thermal.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating Thermal Material and Properties Create the material and property collectors before creating the component collectors. 1. In the Model Browser, right-click and select Create > Material. A default MAT1 material displays in the Entity Editor. 2. For Name, enter steel.

3. Check the box in front of MAT4. MAT4 card image appears below MAT1 in the Entity Editor. The MAT1 card defines the isotropic structural material. MAT4 card is for the constant thermal material. MAT4 uses the same material ID as MAT1. 4. Enter the following values for the material, steel, in the Entity Editor. 11

[E] Young's modulus

2.1 x 10

[NU] Poisson's ratio

0.3

[RHO] Material density

7.9 x 10 Kg/m

[A] Thermal expansion coefficient

1.0 x 10

[K] Thermal conductivity

73W / m °C

[H] Heat transfer coefficient

40W / m °C

Pa

3

-5

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3

/ °C

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Figure 97: Material Entity Editor

A new material, steel, is created with both structural and thermal properties. 5. In the Model Browser, right-click and select Create > Property. A default PSHELL property displays in the Entity Editor. 6. For Name, enter solid.

7. For Card Image, select PSOLID and click Yes to confirm. 8. For Material, click Unspecified > Material. 9. In the Select Material dialog, select steel and click OK. The property of the solid steel pipe has been created as 3D PSOLID. Material information is linked to this property.

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Linking Material and Property to Existing Structure Once the material and property are defined, they need to be linked to the structure. 1. In the Model Browser, click the component pipe. The Entity Editor opens. 2. For Property, click Unspecified > Property. 3. In the Select Property dialog, select solid and click OK. The material steel now is automatically linked to the component pipe.

Applying Thermal Loads and Boundary Conditions In this exercise the thermal boundary conditions are applied on the model and saved in a predefined load collector spc_temp. A predefined node 4679 specifies the ambient temperature. A predefined node set node_temp contains the nodes on the inside surface of the pipe.

Creating Temperature on the Inner Surface of the Pipe 1. From the Analysis page, click constraints. 2. Go to the create subpanel. 3. Make sure the current selection field is set to nodes. 4. Click nodes >> by sets. 5. Select node_temp and click select. 6. Uncheck the box in front of dof1, dof2, dof3, dof4, dof5, and dof6 and verify that the entry fields are set to 0.0. 7. Set load types = to SPC. 8. Click create. This applies the temperature 0.0 on the inside nodes. In the next step, the temperature value is updated to 60. 9. Click the Card edit icon

.

10. Click loads >> by collector. 11. Check the box in front of spc_temp and click select. 12. Click config= and select const. 13. Click type= and select SPC. 14. Click edit. 15. In the field of D, enter 60.0.

16. Click return three times to go back to the Analysis page.

Creating Ambient Temperature

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1. Make sure spc_temp is the current load collector. 2. From the Analysis page, select the Constraints panel. 3. Go to the create subpanel. 4. Click nodes >>by id. 5. Input the ID of the predefined node 4679. Node 4679 should be highlighted. 6. Uncheck the box in front of dof1, dof2, dof3, dof4, dof5, and dof6 and verify that the entry fields are set to 0.0. 7. Click create.

8. Click the Card edit icon

.

9. Select loads entry. 10. Select the ambient spc just created on the screen. 11. Click config= and select const. 12. Click type= and select SPC. 13. Click edit. 14. In the field of D, enter 20.0. The temperature boundary conditions are created, as shown in the following figure.

Figure 98: Thermal Boundary Conditions

15. Click return three times to go back to the Analysis page.

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Creating CHBDYE Surface Elements Surface elements are to be created to simulate the heat exchange between the solid pipe and the surrounding air. A predefined element set elem_convec, which contains the solid elements on the outer surface of the pipe, is used to define the surface elements. 1. Click BCs > Create > Interfaces. 2. For Name, enter convection.

3. For Card Image, select CONVECTION from the drop-down menu. 4. Click Color and select a color from the palette. 5. Click MID to activate it. 6. For Material, click Unspecified > Material. 7. In the Select Material dialog, select steel and click OK. An element group convection and a free convection property PCONV are created. 8. For Slave Entity IDs, select Elements. A panel appears under the modeling window. 9. Click on the switch button beside elems and select faces from the list. 10. Click the highlighted solid elems and select by sets from the selection menu. 11. Select element set elem_convec and click select. 12. Click nodes in face nodes field. 13. Select 4 nodes on the surface face of a solid element, as shown in the following figure.

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Figure 99: Selected Surface Nodes on the Solid Element Outside the Pipe

14. In the break angle = field, enter 89.0.

15. Click add. This adds the CHBDYE surface elements to the solid elements on the outer surface following the same side convention, as shown in the following figure.

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Figure 100: Surface Elements on the Outer Layer of the Pipe

16. Click return to go back to the Create group window.

Defining Convection Boundary Condition to Surface Elements 1. Click the Card Edit icon

.

2. Select elems. 3. Click elems > by group. 4. Check the box in front of CONVECTION and click select. 5. Click config= and select slave4. 6. Click type= and select CHBDYE4. 7. Click edit and go to the CHBDYE Card Image panel. 8. Check the box in front of CONV. 9. Click TA1 and input the ambient node ID 4679, as shown below.

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Figure 101: Defining the Convection Boundary Condition

10. Click return three times to go back to the Analysis page.

Creating Heat Transfer Load Step An OptiStruct steady state heat convection loadstep is created, which references the thermal boundary conditions in the load collector spc_temp. The gradient, flux, and temperature output for the heat transfer analysis is also requested in the Loadsteps panel. 1. In the Model Browser, right-click and select Create > Load Step. 2. A default loadstep displays in the Entity Editor. 3. For Name, enter heat_transfer.

4. Click on the Analysis type field and select Heat transfer (steady state) from the drop-down menu. 5. For SPC, click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select spc_temp and click OK. 7. Check the box next to Output. 8. Activate the options of FLUX and THERMAL on the sub-list. 9. Activate the FORMAT fields for both outputs and select H3D format. 10. Activate the OPTION fields for both outputs and select ALL. The FORMAT and OUTPUT fields for THERMAL output may open up a new window. Click on the first field in the window to select the corresponding values. FLUX and THERMAL output can also be requested in the Control cards panel on the Analysis page.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 102: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter thermal_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the thermal_complete.fem was written. The thermal_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Gradient temperatures and flux contour results for the steady state heat conduction analysis and the stress and displacement results for the structural analysis are computed from OptiStruct. HyperView will be used to post process the results. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. On the Results toolbar, click

to open the Contour panel.

4. Select the first pull-down menu below Result type and select Grid Temperatures(s). 5. Click Apply. You may have to use Edit Legend in the Contour panel to get the contour, as shown in Figure 103. A contour plot of grid temperatures is created.

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6. Select the first pull-down menu below Result type and select Element Fluxes (V). 7. Click Apply. You may have to use Edit Legend in the Contour panel to get the contour. Both temperature and flux contour plots are shown in Figure 103.

Figure 103: Results of Heat Transfer Analysis

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OS-T: 1090: Linear Transient Heat Transfer Analysis of an Extended Surface Heat Transfer Fin This tutorial outlines the procedure to perform a linear transient heat transfer analysis on a steel extended-surface heat transfer fin attached to the outer surface of a system generating heat flux (Example: IC engine). The extended surface heat transfer fin analyzed in this tutorial is one of many from an array of such fins connected to the system. The fins draw heat away from the outer surface of the system and dissipate it to the surrounding air. The process of heat transfer out of the fin depends upon the flow of air around the fin (Free or forced convection). In the current tutorial, the focus is on transient heat transfer through heat flux loading and free convection dissipation. An extended surface heat transfer fin made of steel is illustrated in Figure 104. To meet certain structural design requirements, the fin is bent at 90° at approximately a quarter of its length. Tip: A free convection analysis is conducted in this tutorial; however, if forced fluid flow (forced convection) is allowed over the outer surface of the system, then offsetting the fins from each other periodically, interrupts the growth of a thermal boundary layer and a reduction in flow velocity occurs due to form drag, resulting in a higher heat transfer rate.

Figure 104: Extended Surface Heat Transfer Fin for Convective and Conductive Transient Heat Transfer

The extended surface heat transfer fin shown in Figure 104 is meshed with CHEXA elements in HyperMesh and a transient heat transfer analysis is performed in HyperMesh using the Altair OptiStruct 2 solver. A typical heat flux load of 100 KW/m is applied to the face connected to the outer surface of the system. An ambient temperature of 25°C is assumed and all material properties are assumed to remain

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constant with temperature and time. Free (Natural) convection is assumed over the entire surface of the material, wherein heat transfer between the surface of the fin and the surrounding air occurs due to a complex mechanism of density differences as a result of temperature gradients. Tip: In its simplest form, natural convection can be explained as the transfer of heat from the hot surface to a layer of cold air just above it, leading to an increase of temperature within that layer causing a drop in air density. The hot air (less dense) then rises vacating space for a layer of cold air (more dense) that takes its place and so on in a continuous pattern until (if) steady-state is reached. In reality, however, the process of natural convection is highly complex due to the complexities in fluid flow and extensive experimental correlation is required for accurate analysis.

Prerequisites 1. The latest version of HyperMesh, HyperView and OptiStruct software installations. Transient heat transfer analysis is available only in HyperMesh version-12.0.110, HyperView version-12.0.110 and OptiStruct version-12.0.202 and later. 2. The heat_transfer_fin.fem solver deck is available from the optistruct.zip file. Refer to Accessing the Model Files.

Figure 105: Heat Exchanger Fin Model for Transient Heat Transfer Analysis

Linear Transient Heat Transfer Analysis Overview Linear transient heat transfer analysis can be used to calculate the temperature distribution in a system with respect to time. The applied thermal loads can either be time-dependent or time-invariant; transient thermal analysis is used to capture the thermal behavior of a system over a specific period in time. The basic finite element equation for transient heat transfer analysis is given by: (1) Where,

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Heat capacity matrix Conductivity matrix Boundary convection matrix due to free convection Temperature derivative with respect to time Unknown nodal temperature Thermal loading vector The differential equation (Equation 1) is solved to find nodal temperature

at the specified time steps.

The difference between Equation 1 and the steady-state heat transfer equation is the term, captures the transient nature of the analysis.

that

Checkpoint Steady-state heat transfer analysis, generally, is sufficient for a wide variety of applications. However, in situations where the system properties vary significantly over time the transient nature of heat transfer must be considered. Some examples are the relatively slow heating up of airplane gas turbine compressor disks compared to the turbine casing leading to aerodynamic issues during takeoff or the analysis of the time taken for the onset of frostbite in fingers or toes.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the heat_transfer_fin.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating Thermal Material and Property The imported model only contains the component and predefined element sets for boundary condition creation. Now create a thermal material that can be assigned to this component. 1. In the Model Browser, right-click and select Create > Material. A default MAT1 material displays in the Entity Editor. 2. For Name, enter steel.

3. For Card Image, select MAT4 and click Yes to confirm. 4. Enter the following material property values for the MAT4 Data Entry. [K] Thermal Conductivity

7.3 x 10-2W/mm °C

[CP] Heat Capacity at constant pressure

508J/Kg °C

[RHO] Density of the material 7.9 x 10-6Kg/mm [H] Coefficient of heat transfer

2

3

4 x 10-5W/mm °C

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Figure 106:

Since you are conducting a purely heat transfer analysis, structural isotropic properties (for example, MAT1 card) are not required. Also, it is assumed that the thermal material properties (MAT4) are temperature independent. A new material, steel, is created with thermal properties necessary for a transient heat transfer analysis. Now, create the solid property for this model referencing the PSOLID entry and connect the material, steel, to this property; the property can then be assigned to the existing component. 5. In the Model Browser, right-click and select Create > Property. A default PSHELL property displays in the Entity Editor. 6. For Name, enter solid.

7. For Card Image, select PSOLID and click Yes to confirm. 8. For Material, click Unspecified > Material. 9. In the Select Material dialog, select steel and click OK.

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Figure 107:

Linking Thermal Material and Property to the Structure Once the material and property are defined, they need to be linked to the structure. 1. In the Model Browser, click the component auto1. The Entity Editor opens. 2. For Property, click Unspecified > Property. 3. In the Select Property dialog, select solid and click OK. The material steel now is automatically linked to the component auto1.

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Figure 108:

Creating Transient Heat Transfer Analysis Time Steps A transient analysis captures the behavior of the system over a specific period of time. Therefore, a time period of interest for your system is defined. A time period of 500 seconds (8 minutes, 20 seconds) is defined with results output every 10 seconds. A load collector is created for this purpose and the TSTEP entry is referenced, as shown below. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter Time Steps.

3. For Card Image, select TSTEP. 4. For TSTEP_NUM, enter a value of 1. 5. Click

and enter the number of time steps (N) = 50 and set each time increment (DT) to 10.

This encompasses a total time period of 500 seconds in which to capture the behavior of the system.

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Figure 109:

6. Click Close.

Creating Transient Heat Transfer Analysis Initial Conditions Since the temperature profile of the system varies over time, the initial grid point temperature profile must be set to specify the starting point for the analysis. You assume that the temperature of the entire system is equal to 25°C at T=0 seconds, the TEMPD Bulk Data Entry sets the initial temperatures. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter Initial Conditions. 3. For Card Image, select TEMPD. 4. For T1, enter a value of 25.

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Figure 110:

Applying Ambient Temperature Boundary Conditions Ambient temperature thermal boundary conditions is applied on the model by creating specific load collectors for each. The ambient temperature is controlled using an SPCD entry, as this will allow an ambient temperature variation over time to help mimic such physical requirements (if any).

Creating a Time-variant Ambient Temperature A time variable ambient temperature can be created by referencing an SPCD entry via a TLOAD1 Data Entry. The time variable nature of the ambient temperature can be captured using a TABLED1 entry also referenced by the TLOAD1 data. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter Ambient SPCD TLOAD1.

3. For Card Image, select TLOAD1. The TLOAD1 fields will be updated after the creation of the corresponding SPCD and TABLED1 Data Entries. 4. Create another load collector named Ambient SPCD, and for Card Image, select None. The newly created Ambient SPCD load collector is the current load collector (look at the right bottom corner of the screen to verify that Ambient SPCD is displayed). 5. If the Ambient SPCD load collector is not specified, right-click Ambient SPCD in the Model Browser and click Make Current.

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Figure 111: Displaying the Current Load Collector - Ambient SPCD

6. Next, create the amplitude (constant part) of the time variant ambient temperature using an SPCD Data Entry. Click BCs > Create > Constraints. 7. The ambient temperature is set by using the SPCD Data Entry to control an existing node outside the actual structure. In the Constraints panel, click nodes > by id, enter 5672 in the id= field and press Enter. The ambient node is highlighted in the Entity Editor above the structure. 8. Enter 5.0 in the size= field and uncheck the boxes beside all the degrees of freedom (dof1 through dof6) and enter 0.0 in all the fields next to the dof#. 9. For load types =, select SPCD.

Figure 112: Creating an SPCD Entry to Control the Ambient Temperature

10. Click create/edit and enter 25.0 in the D field on the SPCD Data Entry. This creates an SPCD referencing the ambient node specifying a temperature of 25°C. 11. Click return twice to go back to the Analysis page.

12. Next, create another load collector to define the time variant nature of the ambient temperature. This is done by specifying a TABLED1 entry referenced by the previously created TLOAD1 entry.

13. Create a new load collector named Ambient SPCD Table, and set the Card Image as TABLED1. 14. For TABLED1_NUM, enter 2 and press Enter.

15. In the table, enter x(1) = 0.0, y(1) = 1.0, x(2) = 500.0, and y(2) = 1.0. 16. Click Close.

Tip: In this tutorial, a constant ambient temperature (the values of y(1) and y(2) are the same leading to a constant temperature distribution over the first 500 seconds) is defined; however, this demonstrates the procedure to use a TABLED1 entry to specify a time variant ambient temperature as well. To do this, specify different values for the y# fields and depending on the type of variation required, select from LINEAR or LOG options. Checkpoint The SPCD and its corresponding table are linked to the previously created TLOAD1 entry.

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Figure 113: Process to specify a time-variant SPCD

17. In the Model Browser, click the Ambient SPCD TLOAD1 load collector. It is displayed in the Entity Editor. 18. For EXCITEID, select the Ambient SPCD load collector from the menu. 19. For TYPE, select DISP, then click TID and select the Ambient SPCD Table load collector menu. All entities referenced by SPCD entries should also be constrained by SPC data entries. The value of the corresponding SPC referencing an ambient point controlled via an SPCD by TLOAD1/2 entries should be equal to zero (0.0). 20. Create a new load collector named Ambient SPC and for Card Image, select None.

21. Make sure that the newly created load collector Ambient SPC is current and click BCs > Create > Constraints and click nodes in the Constraints panel. 22. Select by id from the extended menu, enter 5672 and press Enter. The ambient node is highlighted in the modeling window above the structure. 23. Enter 5.0 in the size= field and uncheck the boxes beside all the degrees of freedom (dof1 through dof6) and enter 0.0 in all the fields next to the dof#. 24. For load types =, select SPC.

Figure 114: Creating the SPC Boundary Condition

25. Click create/edit and enter 0.0 in the D field on the SPC Data Entry. This creates an SPC referencing the same ambient node that is controlled by the SPCD Data Entry. 26. Click return twice to go back to the Analysis page.

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Applying Heat Flux Load Ambient temperature thermal boundary conditions have been assigned to the model and heat flux load from the outer surface of the engine (to which the fin is attached) is applied on the model. A time2 varying heat flux load of 0 to 0.1 W/mm from 0 to 500 seconds is used for the analysis of this fin. This load is applied on the model by creating specific load collectors for the corresponding TLOAD1, QBDY1 and TABLED1 entries similar to the procedure used for the ambient temperature SPCD definition.

Creating a Time-variant Linearly Increasing Heat Flux Load A time variable ambient temperature can be created by referencing an SPCD entry via a TLOAD1 Data Entry. The time variable nature of the ambient temperature can be captured using a TABLED1 entry also referenced by the TLOAD1 data. 1. Create a new load collector named Heat Flux TLOAD1 and select TLOAD1 as the Card Image. The TLOAD1 fields will be updated after the creation of the corresponding QBDY1 and TABLED1 Data Entries. 2. Create another load collector named Heat Flux QBDY1 and select None as the Card Image. The newly created Heat Flux QBDY1 load collector is the current load collector (look at the right bottom corner of the screen to verify if Heat Flux QBDY1 is displayed). 3. If the Heat Flux QBDY1 load collector is not specified, right-click Heat Flux QBDY1 in the Entity Editor and click Make Current.

Figure 115: Displaying the Current Load Collector - Heat Flux QBDY1

4. An interface is now created between the heat flux source and the solid elements on the surface of the fin. This is done by clicking BCs > Create > Interfaces and specifying conduction_interface in the Name field of the Create group dialog.

5. For Card Image, select CONDUCTION from the drop-down menu and click Yes to confirm. 6. For Slave Entity IDs, click on the yellow Elements panel. A panel appears under the modeling window. 7. Click on the switch button beside elems and select faces from the list. 8. Click the highlighted solid elems and select by sets from the selection menu. 9. Check the box next to Element_set_Flux and click select. The predefined element set is now highlighted in white on the model.

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Figure 116: Highlighted Element Set is Displayed in White

Tip: The break angle helps find adjacent solid faces for the same element set, however, since this surface element set generation requires only one face, the value of the break angle is not germane in this situation. 10. Click nodes and select the nodes in the Figure 117.

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Figure 117: Selecting the Nodes on the Highlighted Surface for Conduction Surface Element Creation

11. Click add and return to go back to the Create group dialog. 12. Click Close. A conduction interface is created because QBDY1 data can only reference surface elements and the conduction interface helps us create a set of surface elements at the surface where heat flux is input.

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Figure 118: Newly Generated Surface Elements are Displayed in Blue

13. Next, create the amplitude (constant part) of the time variant heat flux using a QBDY1 Data Entry. Do this by clicking on BCs > Create > Flux.

Figure 119: Accessing the Flux Creation Panel

14. Click elems, select by group and select conduction_interface. The newly created surface elements are highlighted in white on the model. 15. Enter 0.1 in the value= field and select QBDY1 in the load types = field. Specify any low value in the magnitude% =field to assign a value to the size of the display label for the flux load.

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Figure 120: Heat Flux Load Panel

16. Click create and return to go back to the Analysis page. 17. Next, create another load collector to define the linear time variant nature of the heat flux. This is done by specifying a TABLED1 entry referenced by the previously created TLOAD1 entry. 18. Create a new load collector named Heat Flux Table and select TABLED1 as the Card Image. 19. For TABLED1_NUM, enter 2 and press Enter. 20. Click

= 1.0.

next to Data. In the pop-out window, enter x(1) = 0.0,y(1) = 0.0, x(2) = 500.0 and y(2) Tip: In this tutorial, a linearly incremental heat flux load (the values of y(1) and y(2) are 0 and 1 leading to a linearly increasing heat flux distribution over the first 500 seconds) is defined.

Checkpoint The QBDY1 flux load and its corresponding table are linked to the previously created TLOAD1 entry.

Figure 121: Process to Specify a Time-Variant SPCD

21. In the Model Browser, click the Heat Flux TLOAD1 load collector. The entry is displayed in the Entity Editor below. 22. For Card Image, select TLOAD1. 23. For EXCITEID, select the Heat Flux QBDY1 load collector from the pop-out table and click OK. 24. For TYPE, select LOAD, then click TID and select the Heat Flux Table from the pop-out table and click OK.

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Adding Free Convection Free convection is assigned in a similar manner to the procedure used for the creation of the conduction interface. Free convection is, however, automatically assigned to all heat transfer subcases and the PCONV and CONV entries should refer to the material, steel, and the ambient temperature. The ambient temperature calculates the amount of heat transferred through free convection.

Creating Surface Elements for Free Convection Surface elements are to be created to simulate the heat exchange between the fin surface and the surrounding air. A predefined element set Element_set_convection, which contains the solid elements on the outer surface of the fin defines the surface elements at the interface. 1. An interface is now created between the surrounding air and the solid elements on the surface of the fin. This is done by clicking BCs > Create > Interfaces and specifying convection_interface in the Name field of the Create group pop-up table.

2. For Card Image, select CONVECTION from the drop-down menu and click Yes to confirm. 3. For Slave Entity IDs, click on the yellow Elements panel. A panel appears under the modeling window. 4. Click on the switch button beside elems and select faces from the list. 5. Click the highlighted solid elems and select by sets from the selection menu. 6. Select element set Element_set_Convection and click select. The predefined element set is now highlighted in white on the model.

Figure 122: The Highlighted Element Set is Displayed in White

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7. Click nodes next to face nodes, this highlights the same element set in black. Click any four nodes on all highlighted faces of the model as shown in Figure 123 and Figure 124 and specify a break angle of 89°. Tip: The break angle helps find adjacent solid faces for the same element set, all adjacent faces with the angle between surface normals less than the specified break angle are selected for surface element creation. 8. Click add and return to go back to the Analysis page. 9. Click the MID field and select steel from the menu.

Figure 123: Selecting the Nodes on Four of the Seven Highlighted Surfaces for Convection Surface Element Creation

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Figure 124: Selecting Nodes on the Three Remaining Highlighted Surfaces for the Creation of a Convection Interface

The newly created CHBDYE surface elements are displayed in yellow, as shown in Figure 125 below.

Figure 125: Newly generated CHBBDYE Surface Elements are Displayed in Yellow on the Model

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10. Click Close. 11. Next, the convection boundary condition is defined by referencing the ambient temperature in the CONV Data Entry. This is done by clicking on the Card Edit icon

and selecting the elems entry.

12. Click elems >> by group and select convection_interface from the menu. 13. Click config= and select slave4. 14. Click type= and select CHBDYE4. 15. Click edit and go to the CHBDYE Card Image panel. 16. Check the box beside CONV. Click TA1 and input the ambient node ID 5672. 17. Click return twice to go back to the Analysis page.

Combining TLOAD1 Entries into a DLOAD Entry Two different TLOAD1 entries have been defined and since they are to be referenced in the same subcase they should be combined using a DLOAD Data Entry. 1. Create a new load collector named Combined Flux and Convection and select DLOAD as the card image. 2. For S, enter 1.0.

3. As only a simple linear addition of the two TLOAD1 entries are required, for DLOAD_NUM, enter 2 and press Enter. 4. Click

next to Data below the DLOAD_NUM field. In the DLOAD_NUM pop-up window, enter

S(1) = 1.0 and S(2) = 1.0.

5. For L(1), select Ambient SPCD TLOAD1 from the menu and for L(2), select Heat Flux TLOAD1 from the menu. 6. Click Close. Checkpoint The DLOAD entry is created as a linear combination of two TLOAD1 entries - Heat Flux TLOAD1 and Ambient SPCD TLOAD1.

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Figure 126: Process to Specify a Time-variant SPCD

Creating a Transient Heat Transfer Load Step An OptiStruct transient heat transfer loadstep is created which references the time steps in the load collector Time Steps, the initial conditions in the load collector Initial Conditions, the heat flux and free convection setup in the load collector Combined Flux and Convection, and the SPC boundary condition in the load collector Ambient SPC. The gradient, flux, and temperature output for the heat transfer analysis is also requested in the Loadsteps panel. 1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter transient heat transfer.

3. Click the Analysis type field and select Heat transfer (transient) from the drop-down menu. 4. For SPC, click Unspecified > Loadcol. 5. In the Select Loadcol dialog, select Ambient SPC from the list of load collectors and click OK to complete the SPC selection. 6. For IC, select Initial Conditions. 7. For TSTEP, select Time Steps. 8. For DLOAD, select Combined Flux and Convection. 9. Check the box next to Output. 10. Activate the options of FLUX and THERMAL on the sub-list. 11. Activate the FORMAT fields for both outputs and select H3D format. 12. Activate the OPTION fields for both outputs and select ALL. The FORMAT and OUTPUT fields for THERMAL output may open up a new window. Click on the first field in the window to select the corresponding values. Note: FLUX and THERMAL output can also be requested in control cards panel on Analysis page.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 127: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter heat_transfer_fin_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the heat_transfer_fin_complete.fem was written. The heat_transfer_fin_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing Results Grid temperatures, element temperature gradients and flux contour results are computed for the transient heat transfer analysis and HyperView are used to post-process the results. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. On the Results toolbar, click

to open the Contour panel.

4. Select the first pull-down menu below Result type and select Grid Temperatures(s).

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Figure 128: Contour Plot Panel in HyperView

5. Click Apply, select Time = 5.0000000E+02 from the Results Browser. A contour plot of grid temperatures at the final time step is created as shown in Figure 129.

Figure 129: Grid Temperature Contour for the Final Time Step (500 seconds) - WITH FREE CONVECTION

Checkpoint In Figure 129, this is the grid point temperature plot after 500 seconds. The system is input a linearly 2 increasing heat flux from 0 to 0.1 W/mm from 0 to 500 seconds respectively. Therefore, a physical correlation can be the effect of starting an IC engine to full capacity wherein the flux transmitted to the outer surface linearly increases with time. Note that the flux patterns in actuality may be different and may fluctuate based on the duration of the power cycles. The maximum temperature of 81.3°C predictably occurs at the elements closest to the heat flux loading site and the minimum temperature of 29.5°C occurs at elements farthest from the heat source. 6. Click Apply, select Time = 2.0000000E+01 from the Results Browser. A contour plot of grid temperatures is created, as shown in Figure 130.

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Figure 130: Grid Temperature Contour Plot after 20 Seconds - WITH FREE CONVECTION

7. Select the first pull-down menu below Result type and select Element Fluxes (V). 8. Click Apply, select Time = 5.0000000E+02 from the Results Browser to view the element flux results after 500 seconds in Figure 132. In a practical setting, you can also see the effect of free convection in the reduction of temperature at the outer surface of the system. Convection (due to the extended surface area) allows a larger amount of heat to be drawn out of the system when compared to the absence of an extended surface fin. This is evident in the temperature of the outer surface of the system after 500 seconds in the absence of convection heat loss.

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Figure 131: Grid Temperature Contour Plot after 500 Seconds - WITHOUT FREE CONVECTION

The maximum temperature at the outer surface of the heat source system is 125.3°C which is an increase of 44°C in 500 seconds. Therefore using an extended surface fin is a very effective way to reduce the temperature of a system.

Figure 132: Contour Plot of Element Fluxes after 500 Seconds

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OS-T: 1100 Thermal Stress Analysis of a Printed Circuit Board with Anisotropic Material Properties Printed Circuit Boards (PCB's) are used in electronic components to both mechanically support and provide electrical connections between components. Construction involves etching a thin copper layer that has been deposited onto a non-conductive, glass-fiber/epoxy composite substrate. Electrical components are then mounted to the board and connected to the copper traces with electrical solder. The concentrated, intense heating that occurs during the soldering process creates stresses in the substrate material. In this exercise, you will simulate this process and determine if the stresses and strains resulting from this process are acceptable or not. The model makes use of solid hexahedral (CHEXA8) elements with a thin skin of shell elements (CQUAD4) on the outside faces. The consistent unit system used in this simulation are: kg, mm, GPa, kN and °C

Figure 133:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the circuit_board.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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3. Click Open. The circuit_board.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating MAT9 Material for Solid Elements The MAT9 material type defines the properties for linear, temperature independent, anisotropic materials. This material model is well suited to this tutorial, due to the composite structure of the substrate. The X, Y and Z orientations of the laminated material have different elastic moduli and thermal expansion coefficients. The MAT9 material applied to solid elements allows a simplification of the model over using a shell model of the composite, with the individual ply layer properties and orientations defined. 1. In the Model Browser, right-click and select Create > Material. 2. For Name, enter PCB_solids.

3. For Card Image,select MAT9 and click Yes to confirm. 4. Enter the following values for the oriented elastic and shear modulus of the composite: G11

17.0

G22

16.2

G33

7.00

G44

4.93

G55

4.70

G66

2.03

5. Enter the following values for the thermal expansion rates and reference temperature: A1

1.6e-5

A2

1.9e-5

A3

8.0e-5

TREF

10.0

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Figure 134:

Creating MAT2 Material for Shell Elements You should still be in the materials/create panel from the previous step. 1. In the Model Browser, right-click and select Create > Material. 2. For Name, enter PCB_shells.

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OptiStruct Tutorials Basic Small Displacement Finite Element Analysis 3. For Card Image, select MAT2 and click Yes to confirm. 4. Enter the following values for the shell element material properties: G11

17.0

G22

16.2

G33

4.90

A1

1.6e-5

A2

1.9e-5

TREF

10.0

Creating Properties with a Material Reference 1. In the Model Browser, right-click and select Create > Property. 2. For Name, enter shell.

3. For Card Image, select PSHELL. 4. For Material, click Create > Material. 5. In the Select Material dialog, select PCB_shells from the list of materials and click OK to complete the material selection. 6. Enter the thickness for the shell component by clicking T, and enter 0.001.

Figure 135:

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7. Repeat steps 1 to 6 to create another property with name Solids, with Card Image set as PSOLID and Material as PCB_solids. 8. In the Model Browser, click the pcb_solids component. The component entry is displayed in the Entity Editor below. 9. For Property, click Unspecified > Property. 10. In the Select Property dialog, select Solids and click OK to complete the property selection. 11. Repeat steps 8 to 10 for both solder_pads and shell_faces selecting shell for the property name.

Creating Displacement Constraints at the Mounting Holes 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter constraints.

3. Leave Card Image set to None. 4. Select a suitable color.

Figure 136:

5. Click BCs > Create > Constraints to open the Constraints panel. 6. Click nodes > by sets. 7. Select the constrain_nodes entity set and click select. 8. Leave all 6 degrees of freedom selected and click create. 9. Click return to go back to the main menu.

Creating Applied Temperature Loads at the Solder Pads 1. Create a new load collector named temperature_loads. 2. Leave Card Image set to None.

3. Click BCs > Create > Interfaces to open the Temperatures panel. 4. Click nodes > by collector. 5. Check the box next to the solder_pads component.

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6. Click select. 7. Verify that constant value (the field label specifies value=) is selected and enter 345.0. 8. Verify the load types= is set to TEMP.

9. Click create to create the temperature_loads. 10. Click return to go back to the main menu.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step. A default load step template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter thermal_loading.

3. For Analysis type, select Linear Static from the drop-down menu. 4. For SPC, select Unspecified > Loadcol. 5. In the Select Loadcol dialog, select constraints and click OK. 6. For TEMP, click Unspecified > TEMP. 7. In the Select Loadcol dialog, select temperature_loads and click OK. An OptiStruct loadstep has been created, which references the inertia relief support points in the load collector SPCs and the forces in the load collector static_loads.

Adding Control Cards to the Analysis 1. Click Setup > Create > Control Cards to open the Control Cards panel. 2. Click next to advance until OUTPUT is available, click OUTPUT to add card requesting output results format. 3. For the number_of_outputs field on the lower part of the panel, enter 2.

4. Set one of the KEYWORD to OP2 to request the OP2 format results file, and set the second output as H3D format. The frequency (FREQ) of the output can be set as ALL. 5. Click return to go back to the Control Cards panel. 6. Click next to advance to the second page of control cards, then once more to go to the third page. 7. Activate the SCREEN card with the OUT option. 8. Return to the Control Card panel. 9. Select GLOBAL_OUTPUT_REQUEST on the first page to access the output settings. 10. Activate the STRAIN option to request strain results output. Leave the default settings for this card. 11. Click return twice to get back to the main menu.

Submitting the Job

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1. From the Analysis page, click the OptiStruct panel.

Figure 137: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter circuit_board for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the circuit_board.fem was written. The circuit_board.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

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OS-T: 1110 Modal Analysis Setup In this tutorial, you continue to gain an understanding of the basic concepts for creating a OptiStruct input file. More specifically, learn how to set up a model for modal analysis, specify solver specific controls and also submit an input file to the solver from HyperMesh. The channel_brkt_modal.hm file is used for this tutorial. It contains the bracket and channel assembly pictured below. To complete the setup of the model for a modal analysis with OptiStruct, you need to define a normal modes SUBCASE, containing METHOD and SPC statements.

Figure 138:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the channel_brkt_modal.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The channel_brkt_modal.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Reviewing and Editing the Materials This step can be done from the Model Browser. 1. In the Model Browser, expand the Material folder to show the two materials in the model. 2. Click aluminum. The material entry is displayed in the Entity Editor. 3. For RHO, enter 2.7e-9.

4. Repeat steps 1 to 3 to input an RHO value of 7.9e-9 for the steel entry.

Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter modal.

3. Click Color and select a color from the color palette. 4. Set Card Image to EIGRL. 5. For ND, enter 10.

ND specifies the number of modes to extract.

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Figure 139:

6. Create another load collector. a) For Name, enter constraints. b) For Card Image, select None.

Applying Constraints (OptiStruct SPC) on the Channel 1. Expand the Component folder in the Model Browser. 2. Click the geometry icon

next to the channel component to turn the geometry display on.

3. Click the Isometric View icon

in the toolbar.

You are going to create the SPC constraints on the nodes along the lines on the perimeter of the channel's bottom surface, as shown in the image below.

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Figure 140: Apply Constraints on the Channel

4. Click BCs > Create > Constraints to open the Constraints panel. 5. Switch the entity selector to lines. 6. Select the six lines on the perimeter of the channel's bottom surface. To view the selected lines clearly, switch to Transparent Elements mode, as shown below:

Figure 141:

7. Activate degrees of freedom (DOF) 1 through 6. • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 8. For size =, enter 10. The display size of the constraints is reduced. 9. Click create > return to exit the panel.

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Mapping the Constraints Use the Load on Geom panel in this step. 1. From the Analysis page, click load on geom. 2. Click loadcols, and select constraints. 3. Click select to complete the selection of load collectors. 4. Click map loads. A constraint is at each node associated to the geometry lines. 5. Click return to exit the panel.

Defining the Load Step Use the Load Step Entity Editor in this step. Define the loadstep to contain the load collectors constraints and modal. 1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter normal_modes.

3. For Analysis type, select Normal modes. 4. For METHOD(STRUCT), select modal. 5. For SPC, select the load collector constraints.

Defining the Formats of Result Files In the Control Cards panel, use the OUTPUT card to add two output requests for the Altair H3D and HyperMesh .res formats. 1. Click Setup > Create > Control Cards to open the Control Cards panel. 2. Click next to go to the next panel menu of control cards. 3. Select the control card OUTPUT. Notice in the card image the one OUTPUT line is set to a default value. This specifies OptiStruct to output the results to a HyperMesh command file. 4. Click the default value and select H3D from the pop-up menu. 5. For number_of_outputs =, enter 2. A second OUTPUT line appears in the card image. 6. Click the default value again and select HM for the second output type. This specifies OptiStruct to output results to a H3D file and a . res file, which can be viewed in HyperView Player. Also, an HTML report file is output and the H3D file is embedded in it. 7. Click return to return to the Control Cards panel. Notice: The OUTPUT button is green. This indicates the card is exported to the OptiStruct input file. 8. Click return to exit the panel.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 142: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter modal_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the modal_analysis.fem was written. The modal_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

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Advanced Small Displacement Finite Element Analysis Advanced Small Displacement Finite Element Analysis

This chapter covers the following: •

OS-T: 1300 Direct Frequency Response Analysis of a Flat Plate (p. 166)

•

OS-T: 1305 Modal Frequency Response Analysis of a Flat Plate (p. 177)

•

OS-T: 1310 Direct Transient Dynamic Analysis of a Bracket (p. 189)

•

OS-T: 1315 Modal Transient Dynamic Analysis of a Bracket (p. 197)

•

OS-T: 1320 Nonlinear Gap Analysis of an Airplane Wing Rib (p. 206)

•

OS-T: 1325 Random Response Analysis of a Flat Plate (p. 219)

•

OS-T: 1330 Acoustic Analysis of a Half Car Model (p. 226)

•

OS-T: 1340 Fatigue (Stress - Life) Method (p. 239)

•

OS-T: 1350 Fatigue (Strain - Life) Method (p. 263)

•

OS-T: 1360 NLSTAT Analysis of Gasket Materials in Contact (p. 289)

•

OS-T: 1365 NLSTAT Analysis of Solid Blocks in Contact (p. 302)

•

OS-T: 1370 Complex Eigenvalue Analysis of a Reduced Brake System (p. 316)

•

OS-T: 1371 Brake Squeal Analysis of Brake Assembly (p. 321)

•

OS-T: 1372 Rotor Dynamics of a Hollow Cylindrical Rotor (p. 327)

•

OS-T: 1375 Response Spectrum Analysis of a Structure (p. 334)

•

OS-T: 1380 Computation of Equivalent Radiated Power (p. 344)

•

OS-T: 1385 Heat Transfer Analysis on Piston Rings with GAP Elements (p. 349)

•

OS-T: 1390 Pretensioned Bolt Analysis of an IC Engine Cylinder Head, Gasket and Engine Block System (p. 357)

•

OS-T: 1392 Node-to-Surface vs Surface-to-Surface Contact (p. 379)

•

OS-T: 1393 Basics of Contact Properties and Debugging (p. 390)

5

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OS-T: 1300 Direct Frequency Response Analysis of a Flat Plate This tutorial demonstrates how to import an existing FE model, apply boundary conditions, and perform a finite element analysis on a flat plate. The flat plate is subjected to a frequency-varying unit load excitation using the direct method. Postprocessing is done in HyperView and HyperGraph to visualize deformations, mode shape response, and frequency-phase output characteristics.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the direct_response_flat_plate_input.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Model Applying Loads and Boundary Conditions In the following steps, the model is constrained at one edge. A unit vertical load is applied acting upwards in the positive z-direction at a point on a free edge corner of the plate.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 1. Click the Model tab. 2. In the Model Browser, right-click and select Create > Load Collector. 3. For Name, enter spcs.

4. Click Color and select a color from the color palette. 5. Set the Card Image to None. A new load collector, spcs is created. 6. In the Model Browser, right-click and select Create > Load Collector. 7. For Name, enter unit-load.

8. Click Color and select a different color from the color palette. A new load collector, unit-load is created.

Creating Constraints 1. In the Model Browser, expand Load Collector, right-click spcs > Make Current.

Figure 143:

2. Click the Display Numbers icon

.

3. Click nodes >> displayed. 4. Select on (green button). All of the node numbers on the flat plate should now be displayed. 5. Click return to go back to the main menu. 6. Click BCs > Create > Constraints to open the Constraints menu. 7. Click the entity selection switch and select nodes from the pop-up menu. 8. Click nodes and select nodes 5, 29, 30, 31 and 32 (see figure).

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Figure 144: Illustration of which nodes to select for applying single point constraints

9. Constrain dof1, dof2, dof3, dof4 and dof5 (you only need to uncheck dof6). • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 10. Click create. The selected nodes will be free to rotate about the z-axis since dof6 was not checked. 11. Click return to go back to the main menu.

Creating a Unit Load at a Point on the Flat Plate 1. In the Model Browser, right-click on the load collector unit-load and select Make Current. 2. From the Analysis page, click load types. 3. Select constraint = and select DAREA from the extended entity selection menu. 4. Click return to exit the Load Types panel. 5. Click BCs > Create > Constraints to open the Constraints menu. 6. Select node number 19 on the plate by clicking on it (see figure).

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Figure 145: Node Selected for Creating Unit Vertical Load

7. Uncheck all the dof's except dof3, and click the = to the right of dof3 and enter a value of 20.

8. Click load types= and verify that DAREA is selected from the extended entity selection menu. 9. Click create, and then click return. The unit load is applied to the selected node.

Creating a Frequency Range Table 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLED1 from the drop-down menu. 5. For TABLED1_NUM, input a value of 2 and press Enter. 6. Click the Table icon

below TABLED1_NUM and enter x(1) = 0.0, y(1) = 1.0, x(2) = 1000.0

and y(2) = 1.0 in the pop-out window.

7. Click Close. This provides a frequency range of 0.0 to 1000.0 with a constant 1.0 over this range.

Creating a Frequency Dependent Dynamic Load 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter rload2.

3. Click Color and select a color from the color palette.

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4. For Card Image, and select RLOAD2 from the drop-down list. 5. For EXCITEID, click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select unit-load from the list of load collectors and click OK to complete the selection. 7. Similarly select the tabled1 load collector for the TB field. The type of excitation can be an applied load (force or moment), an enforced displacement, velocity or acceleration. The field Type in the RLOAD2 card image defines the type of load. The type is set to applied load by default.

Creating a Set of Frequencies 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter freq1.

3. Click Color and select a color from the color palette. 4. For Card Image, select FREQi from the drop-down menu. 5. Check the FREQ1 option and enter 1 in the NUMBER_OF_FREQ1 field. 6. Click

and enter information in the pop-out window.

a) For F1, enter 20.0. b) For DF, enter 20.0. c) For NDF, enter 49.

7. Click Close. This provides a set of frequencies beginning with 20.0, incremented by 20.0 and 49 frequencies increments.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step. A default load step template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter subcase1.

3. For Analysis type, select Freq.resp (direct) from the drop-down menu. 4. For SPC, select SPC from the Select Loadcol pop-out window. 5. For DLOAD, select rload2 from the Select Loadcol pop-out window. 6. For FREQ, select freq1 from the Select Loadcol pop-out window. An OptiStruct subcase has been created which references the constraints in the load collector spc and the unit load in the load collector rload2 with a set of frequencies defined in load collector freq1.

Creating a Set of Nodes 1. In the Model Browser, right-click and select Create > Set.

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2. For Name, enter SETA.

3. For Card Image, select None. 4. Leave the Set Type switch set to non-ordered type. 5. For Entity IDs, select Nodes from the selection switch. 6. Click Nodes and select nodes with IDs 15, 17 and 19. 7. Click proceed.

Creating a Set of Outputs and Mass Factors 1. Click Setup > Create > Control Cards to open the Control Cards panel. 2. Select GLOBAL_OUTPUT_REQUEST and check the box next to DISPLACEMENT. 3. Under FORM(1), select PHASE from the pop-up menu. 4. Under OPTION(1), select SID from the pop-up menu. A new field appears in yellow. 5. Double-click the SID(1) box and select SETA. A value of 1 now appears below the SID field box. This sets the output for only the nodes in set 1.

Figure 146:

6. Click return to exit the GLOBAL_OUTPUT_REQUESTS menu. 7. From the Control Cards panel, select FORMAT. A new window appears in the work area screen. 8. Click number_of_formats = and input a value of 2.

9. On the extended menu in the work area, click on the first FORMAT_V1 field box and select OPTI from the pop-up menu. Using OPTI generates OptiStruct ASCII result files like .disp, .strs, etc. as the output once the run is complete. These files are used during post-processing. 10. Make sure the second field box is set to H3D. 11. Click return to exit the Format menu and return to the Control Cards menu. 12. Click next and select the PARAM subpanel. 13. Scroll down the list using the arrow in the left corner and check the box next to COUPMASS. A new PARAM card appears in the work area screen. 14. Click NO below COUPM_V1 and select YES from the pop-up menu selection.

Selecting YES uses the coupled mass matrix approach for eigenvalue analysis.

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15. Scroll down the list using the arrow in the left corner and check the box next to G. A new PARAM card appears in the work area screen. 16. Click below G_V1 and input a value of 0.06 into the field box.

This value specifies a uniform structural damping coefficient and is obtained by multiplying the critical damping [] ratio by 2.0.

17. Scroll down using the arrow in the left corner and check the box next to WTMASS. A new window appears in the work area screen. 18. Click below WTM_V1 and input a value of 0.00259 into the field box. Three PARAM statements now appear in the pop-up menu on the work screen. This factor is used to input all mass entries in weight units. Using this PARAM multiplies all terms in the mass matrix by this factor.

Figure 147:

19. Click return to exit the PARAM menu. 20. Select the OUTPUT subpanel. 21. Verify that KEYWORD is set to HGFREQ. Using HGFREQ results in a frequency output presentation for HyperGraph. 22. Click on the box beneath FREQ and select ALL from the pop-up selection to choose all outputs results for all frequencies. 23. Leave number_of_outputs set equal to 1. 24. Click return to exit OUTPUT. 25. Click return to exit the Control Cards panel.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 148: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter flat_plate_direct_response for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the flat_plate_direct_response.fem was written. The flat_plate_direct_response.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: flat_plate_direct_response.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. flat_plate_direct_response.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. flat_plate_direct_response.h3d HyperView binary results file. flat_plate_direct_response.res HyperMesh binary results file. flat_plate_direct_response.stat Summary, providing CPU information for each step during analysis process.

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Viewing the Results This step describes how to view displacement results (.mvw file) in HyperGraph and also explains the displacement output (.disp file) from this run. The HyperView results (.h3d file) contains only the displacement results for the three nodes specified in the node set output. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. In the HyperView window, click File > Open > Session. The Open Session File window is displayed. 4. Select the directory where the job was run and select the file flat_plate_direct_response_freq.mvw.

5. Click Open. A warning appears asking whether to discard the existing contents. 6. Click Yes. Two graphs per page and a total of three pages are displayed. The graph title shows Subcase 1 Displacement of grid 15 on page 1. There are two sets of results on this page. The top graph shows Phase Angle verses Frequency (log). The bottom graph shows Magnitude versus Frequency (log) (see Figure 149) for Displacement of grid 15.

Figure 149: Frequency Response of Node 15

7. Click the Next Page icon

.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis This displayed page 2, which shows Subcase 1 (subcase1) - Displacement of grid 17 (see Figure 150).

Figure 150: Frequency Response of Node 17

8. Select the Next Page icon

again to display page 3 containing Subcase 1 (subcase1) -

Displacement of grid 19 (see figure).

Figure 151: Frequency Response of Node 19

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This concludes the HyperGraph results processing. 9. Open the displacement file (.disp) using a text editor. The first field on the second line shows the iteration number, the second field shows the number of data points, and the third field shows the iteration frequency. Line 3, first field shows node number, then x, y, and z displacement magnitudes and x, y and z rotation magnitudes. Line 4, first field shows node number, then x, y, and z displacement phase angles and x, y and z rotation angles.

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OS-T: 1305 Modal Frequency Response Analysis of a Flat Plate This tutorial demonstrates how to import an existing FE model, apply boundary conditions, and perform a modal frequency response analysis on a flat plate. The flat plate is subjected to a frequency varying unit load excitation using the modal method. Postprocessing tools will be used in HyperView and HyperGraph to visualize deformations, mode shape response, and frequency-phase output characteristics.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the modal_response_flat_plate_input.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Model

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Applying Loads and Boundary Conditions In the following steps, the model is constrained at one edge. A unit vertical load is applied acting upwards in the positive z-direction at a point on a free edge corner of the plate. First, the two load collectors (spcs and unit-load) are created. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter spcs.

3. Click Color and select a color from the color palette. 4. For Card Image, set to None. A new load collector, spcs is created.

Figure 152:

5. In the Model Browser, right-click and select Create > Load Collector. 6. For Name, enter unit-load.

7. Click Color and select a color from the color palette. A new load collector, unit-load is created. 8. Click the Display Numbers icon

to open the Numbers panel.

9. Click nodes > displayed. 10. Check the box next to display. 11. Select the green on button. All of the node numbers on the flat plate should now be displayed.

Creating Constraints 1. In the Model Browser, right-click the load collector spcs and select Make Current. 2. Click BCs > Create > Constraints to open the Constraints panel. 3. Click the entity selection switch and select nodes from the pop-up menu. 4. Click nodes and select nodes 5, 29, 30, 31 and 32 (see Figure 153).

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Figure 153: Illustration of Nodes to Select for Applying Single Point Constraints

5. Constrain dof1, dof2, dof3, dof4, and dof5. • DOFs with a check will be constrained while DOFs without a check will be free. • DOFs 1, 2, and 3 are x, y, and z translation degrees of freedom. • DOFs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 6. Click create. The selected nodes will be free to rotate about the z-axis since dof6 was not checked. 7. Click return to go back to the main menu.

Creating a Unit Load at a Point on the Flat Plate 1. In the Model Browser, right-click on the load collector unit-load and select Make Current. 2. Click BCs > Create > Constraints to open the Constraints menu. 3. Select node number 19 on the plate by clicking on it (see figure).

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Figure 154: Node Selected for Creating Unit Vertical Load

4. Uncheck all the dof's except dof3, and click the = to the right of dof3 and enter a value of 1.

5. Click load types= and verify that DAREA is selected from the extended entity selection menu. 6. Click create, and then click return. The unit load is applied to the selected node.

Creating a Frequency Range Table 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLED1 from the drop-down menu. 5. For TABLED1_NUM, input a value of 2 and press Enter. 6. Click the Table icon

below TABLED1_NUM and enter x(1) = 0.0, y(1) = 1.0, x(2) = 1000.0

and y(2) = 1.0 in the pop-out window.

7. Click Close. This provides a frequency range of 0.0 to 1000.0 with a constant 1.0 over this range.

Creating a Frequency Dependent Dynamic Load 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter rload2.

3. Click Color and select a color from the color palette.

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4. For Card Image, and select RLOAD2 from the drop-down list. 5. For EXCITEID, click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select unit-load from the list of load collectors and click OK to complete the selection. 7. Similarly select the tabled1 load collector for the TB field. The type of excitation can be an applied load (force or moment), an enforced displacement, velocity or acceleration. The field Type in the RLOAD2 card image defines the type of load. The type is set to applied load by default.

Creating a Set of Frequencies 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter freq1.

3. Click Color and select a color from the color palette. 4. For Card Image, select FREQi from the drop-down menu. 5. Check the FREQ1 option and enter 1 in the NUMBER_OF_FREQ1 field. 6. Click

and enter information in the pop-out window.

a) For F1, enter 20.0. b) For DF, enter 20.0. c) For NDF, enter 49.

7. Click Close. This provides a set of frequencies beginning with 20.0, incremented by 20.0 and 49 frequencies increments.

Creating the Modal Method for Eigenvalue Analysis 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter eigrl.

3. Click Color and select a color from the color palette. 4. For Card Image, select EIGRL. 5. Click V1 and enter a value 0.0, then click V2 and enter a value of 1000.0.

This specifies a range of frequency between 0 Hz and 1000 Hz for eigenvalue extraction using the Lanczos method.

6. In the Model browser, right-click and select Create > Set. 7. For Name, enter SETA.

8. For Card Image, select None from the drop-down menu. 9. Leave the Set Type switch set to non-ordered type. 10. For Entity IDs, select Nodes from the selection switch. 11. Click on the yellow Nodes button and select nodes with IDs 15, 17 and 19.

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12. Click proceed.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step. A default load step template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter subcase1transient.

3. For Analysis type, select Freq.resp (modal) from the drop-down menu. 4. For METHOD(STRUCT), select Unspecified > Loadcol. 5. From the Select Loadcol dialog, select eigrl. 6. For SPC, select Unspecified > Loadcol. 7. For SPC, select SPC from the Select Loadcol pop-out window. 8. In the Select Loadcol dialog, select spcs and click OK. 9. For DLOAD, select rload2 from the Select Loadcol pop-out window. 10. For FREQ, select freq1 from the Select Loadcol pop-out window. An OptiStruct subcase has been created which references the constraints in the load collector spc and the unit load in the load collector rload2 with a set of frequencies defined in load collector freq1.

Creating a Set of Nodes 1. In the Model Browser, right-click and select Create > Set. 2. For Name, enter SETA.

3. For Card Image, select None. 4. Leave the Set Type switch set to non-ordered type. 5. For Entity IDs, select Nodes from the selection switch. 6. Click Nodes and select nodes with IDs 15, 17 and 19. 7. Click proceed.

Creating a Set of Outputs and Mass Factors 1. Click Setup > Create > Control Cards to open the Control Cards panel. 2. Select GLOBAL_OUTPUT_REQUEST and check the box next to DISPLACEMENT. 3. Click the field box FORM(1) and select PHASE from the pop-up menu. 4. Click the field box OPTION(1) and select SID from the pop-up menu. A new field appears in yellow. 5. Double-click the yellow SID box and select SETA from the pop-up selection on the bottom left corner. A value of 1 now appears below the SID field box. This sets the output for only the nodes in set 1. 6. Click return to exit the GLOBAL_OUTPUT_REQUEST menu.

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7. Click next and select the PARAM subpanel. 8. Scroll down the list using the arrow in the left corner and check the box next to COUPMASS. A new PARAM card appears in the work area screen. 9. Below COUPM_V1 click NO and select YES from the pop-up menu selection. Selecting YES uses the coupled mass matrix approach for eigenvalue analysis. 10. Check the box next to G. A new window appears in the work area screen. 11. Click below G_V1, and input a value of 0.06 into the field box. This value specifies a uniform structural damping coefficient and is obtained by multiplying the critical damping [C/C0] ratio by 2.0. 12. Scroll down using the arrow to the left corner and check the box next to WTMASS. A new window appears in the work area screen. 13. Click below WTM_V1, and input a value of 0.00259 into the field box. Three PARAM statements now appear in the pop-up menu on the work screen. 14. Click return to exit the PARAM menu. 15. Select the OUTPUT card. A new window appears in the work area. 16. Enter 3 in the number_of_outputs field.

17. Set the first KEYWORD to HGFREQ. Using HGFREQ results in a frequency output presentation for HyperGraph. 18. Set the second KEYWORD to OPTI. 19. Set the third KEYWORD to H3D. 20. Double-click on the box beneath FREQ and select ALL from the pop-up selection for all keywords. Selecting ALL will output all optimization iterations. 21. Click return to exit OUTPUT. 22. Click return to exit the Control Cards menu.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 155: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter flat_plate_modal_response for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the flat_plate_modal_response.fem was written. The flat_plate_modal_response.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: flat_plate_modal_response.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. flat_plate_modal_response.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. flat_plate_modal_response.h3d HyperView binary results file. flat_plate_modal_response.res HyperMesh binary results file. flat_plate_modal_response.stat Summary, providing CPU information for each step during analysis process.

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Reviewing the Results This step describes how to view displacement results (.mvw file) in HyperGraph and also how to understand the displacement output (.disp file) from this run. The HyperView results file (.h3d) contains only the displacement results for the three nodes specified in the node set output. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. In the HyperView window, click File > Open > Session. An Open Session File window opens. 4. Select the directory where the job was run and select file flat_plate_modal_response_freq.mvw. 5. Click Open. A discard warning appears.

6. Click Yes. Two graphs per page and a total of three pages are displayed in HyperGraph. The graph title shows Subcase 1 (subcase 1) - Displacement of grid 15 on page 1. 7. Click the Axis toolbar icon

. Select Logarithmic option and use the parameters shown below

to make logarithmic plots of the results.

Figure 156:

There are two sets of results on this page. The top graph shows Phase Angle verses Frequency (log). The bottom graph shows Magnitude verses Frequency (log) (see figure) for Displacement of grid 15.

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Figure 157: Frequency response of node 15

8. Directly underneath the blue graph border, click the Next Page icon

.

Page 2 displays, which shows Subcase 1 (subcase1) - Displacement of grid 17.

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Figure 158: Frequency Response of Node 17

9. Click the Next Page icon

again to display page 3 containing Subcase 1 (subcase1) -

Displacement of grid 19.

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Figure 159: Frequency Response of Node 19

This concludes the HyperGraph results processing. 10. Open the displacement file (.disp) using a text editor. The first field on the second line shows the iteration number, the second field shows number of data points, and the third field shows iteration frequency. Line 3, first field shows node number, then x, y and z displacement magnitudes and x, y and z rotation magnitudes. Line 4, first field shows node number, then x, y and z displacement phase angles and x, y and z rotation phase angles.

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OS-T: 1310 Direct Transient Dynamic Analysis of a Bracket In this tutorial, an existing finite element model of a bracket is used to demonstrate how to perform direct transient dynamic analysis using OptiStruct. HyperGraph is used to post-process the deformation characteristics of the bracket under the transient dynamic loads.

Figure 160: Finite Element Model of the Bracket

The bracket is constrained at the bottom of the two legs. Transient dynamic loads are to be applied at the grid points of the top, flat surface of the bracket around the hole in the negative z direction. The time history of the loading is shown in Figure 161. The direct transient analysis is run for a total time of 4 seconds with the time being divided into 800 increments (that is time step is 0.005). Structural damping has been considered for the model. A concentrated mass element is defined at the center of the spider and z displacements are monitored at the concentrated mass at the center of this hole.

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Figure 161: Time History of Applied Loading

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the bracket_transient.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

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Setting Up the Model Creating a TABLED1 Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLED1 from the drop-down menu. 5. For TABLED1_NUM, enter a value of 4 and press Enter. 6. Click the Table icon

below TABLED1_NUM and enter the values in the pop-out window, as

shown in the figure below.

Figure 162:

7. Click Close. The load collector TABLED1 that defines the time history of the loading has been created.

Creating a TSTEP Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tstep.

3. Click Color and select a color from the color palette. 4. For Card Image, select TSTEP from the drop-down menu. 5. For TSTEP_NUM, enter 1 and press Enter.

6. For N, enter the number of time steps as 800.

7. For DT, enter the time increment of 0.005. The total time applied to the load is: 800 x 0.005 = 4 seconds. This is the time step at which output is requested. NO has a default value of 1.0.

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8. Click Close.

Creating a DAREA Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter darea.

3. Click Color and select a color from the color palette. 4. For Card Image, select NONE. 5. Click BCs > Create > Constraints to open the Constraints panel. 6. Click nodes > by sets. Two sets are displayed. 7. Select force and click select. The nodes that belong to the set force get selected. 8. Uncheck all degrees of freedom (dof), except dof3 by clicking the box next to each, indicating that dof3 is the only active degree of freedom. 9. For dof3, enter a value of -1500. 10. For load types=, select DAREA.

11. Click create. This creates a force of 1500 units applied to the selected nodes in the negative z direction. 12. Click return to go back to the main menu.

Creating a TLOAD1 Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tload1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TLOAD1 from the drop-down list. 5. For EXCITEID , click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select darea from the list of load collectors (created in the last section to define the forces on the top surface of the bracket). 7. Click OK to complete the selection. 8. Similarly select the tabled1 load collector for the TID field (to define the time history of the loading). The type of excitation can be an applied load (force or moment), an enforced displacement, velocity, or acceleration. The field [TYPE] in the TLOAD1 card image defines the type of load. The type is set to applied load by default.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step.

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A default load step template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter transient.

3. For Analysis type, select Transient(direct) from the drop-down menu. 4. For SPC, select SPC from the Select Loadcol pop-out window. 5. For DLOAD, select tload1 from the Select Loadcol pop-out window. 6. Activate TSTEP(TIME) and select the load collector tstep created previously. A subcase is created that specifies the loads and boundary conditions for direct transient dynamic analysis.

Creating Damping Parameters 1. Click Setup > Create > Control Cards to enter the Control Cards panel. 2. Click next to see more cards. 3. Click PARAM to define parameter cards. 4. Scroll down to activate G, click on G_V1, and enter 0.2.

This parameter specifies the uniform structural damping coefficient for the direct transient dynamic analysis.

5. Scroll down to activate W3, click on W3_V1, enter 300.

This parameter is used in transient analysis to convert structural damping to equivalent viscous damping.

6. Click return.

Creating Output Requests 1. Click GLOBAL_OUTPUT_REQUESTS and select DISPLACEMENT and leave the space beneath FORMAT blank. 2. For FORM(1), select BOTH. 3. For OPTION(1), select SID. A yellow button labeled SID appears. 4. Double-click on SID and select center. 5. Select the option for center. This set represents the node at the center of the spider attached to the mass element that is node 395. 6. Click return > next. 7. Click OUTPUT. 8. Under number_of_outputs =, enter 2.

9. For KEYWORD, select H3D and HGTRANS. 10. For FREQ, select ALL for both. 11. Click return twice to exit from the Control Cards panel.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 163: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter bracket_transient_direct for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the bracket_transient_direct.fem was written. The bracket_transient_direct.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: bracket_transient_direct.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. bracket_transient_direct.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. bracket_transient_direct.h3d HyperView binary results file. bracket_transient_direct.res HyperMesh binary results file.

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bracket_transient_direct.stat Summary, providing CPU information for each step during analysis process.

Post-processing Displacement Results 1. From the OptiStruct panel, click HyperView to launch HyperView. 2. Click File > Open > Session. 3. Select the HyperView session file bracket_transient_direct.mvw from the directory in which the input file was run. The following prompt appears:

Figure 164:

4. Click Yes to close the message window. Since the loading is applied only in the z-direction, you are interested in the z-displacement time history of node 395. This file automatically creates plots for the displacement results contained in the file. 5. Click on the Curve Attributes toolbar icon

and turn off the curves X Trans and Y Trans. This

can be done by selecting the individual curves (X Trans and Y Trans) and then by clicking the line attributes Off, as shown below:

Figure 165:

6. Click

to fit the y-axis (that is Z displacement) of node 395 in the GUI.

7. You can change the color and/or line attributes of the curve if you wish to.

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Figure 166: Z-displacement Time History of the Concentrated Mass at Center of Spider for Direct Transient Dynamic Analysis

As can be observed from the above image, the displacements of node 395 are in the negative zdirection as the loading is in the -z direction too. The displacements eventually damp out due to the structural damping present in the model.

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OS-T: 1315 Modal Transient Dynamic Analysis of a Bracket In this tutorial, an existing finite element model of a bracket is used to demonstrate how to perform modal transient dynamic analysis using OptiStruct. HyperGraph is used to post-process the deformation characteristics of the bracket under the transient dynamic loads.

Figure 167: Finite Element Model of the Bracket

The bracket is constrained at the bottom of the two legs. Transient dynamic loads are to be applied at the grid points of the top, flat surface of the bracket around the hole in the negative z-direction. The time history of the loading is shown in Figure 168. The modal transient analysis is run for a total time of 4 seconds with the time being divided into 800 increments (that is time step is 0.005). Modal damping has been defined as 2% critical damping for all the modes. Modes up to 1000 Hz have been considered. A concentrated mass element is defined at the center of the spider and z-displacements are monitored at the concentrated mass at the center of this hole.

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Figure 168: Time History of Applied Loading

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the bracket_transient.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The bracket_transient.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model

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Creating a TABLED1 Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. For Card Image , select TABLED1 from the drop-down menu. 5. For TABLED1_NUM, enter a value of 4 and press Enter. 6. Click the Table icon

below TABLED1_NUM and enter the values in the pop-out window, as

shown in Figure 169.

Figure 169:

7. Click Close. The load collector TABLED1 that defines the time history of the loading has been created.

Creating a TSTEP Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tstep.

3. Click Color and select a color from the color palette. 4. For Card Image, select TSTEP from the drop-down menu. 5. For TSTEP_NUM, enter 1 and press Enter.

6. For N, enter the number of time steps as 800.

7. For DT, enter the time increment of 0.005. The total time applied to the load is: 800 x 0.005 = 4 seconds. This is the time step at which output is requested. NO has a default value of 1.0. 8. Click Close.

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Creating a DAREA Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter darea.

3. Click Color and select a color from the color palette. 4. For Card Image, select NONE. 5. Click BCs > Create > Constraints to open the Constraints panel. 6. Click nodes > by sets. Two sets are displayed. 7. Select force and click select. The nodes that belong to the set force get selected.

Figure 170:

8. Uncheck all degrees of freedom (dof), except dof3 by clicking the box next to each, indicating that dof3 is the only active degree of freedom. 9. For dof3, enter a value of -1500. 10. For load types=, select DAREA.

11. Click create. This creates a force of 1500 units applied to the selected nodes in the negative z direction. 12. Click return to go back to the main menu.

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Creating a TABDMP1 Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabdmp1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABDMP1 from the drop-down list. 5. For TABDMP1_NUM, enter a value of 2 and press Enter. 6. Click

below TABDMP1_NUM and enter the values in the pop-out window, as shown in

Figure 171. 7. Populate the frequency and damping values for frequencies 0 and 1000 Hz and damping to be 0.02, as shown below. This provides a table of damping values for the frequency range of interest.

Figure 171:

8. Click Close to return to the Entity Editor. 9. For TYPE, switch to CRIT to specify critical damping.

Creating a EIGRL Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter eigrl.

3. Click Color and select a color from the color palette. 4. For Card Image, select EIGRL from the drop-down menu. 5. For V1, enter 0.0.

6. For V2, enter 1000.

7. Leave the ND field blank to extract modes up to 1000 Hz.

Creating a TLOAD1 Load Collector 1. In the Model Browser, right-click and select Create > Load Collector.

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2. For Name, enter tload1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TLOAD1 from the drop-down list. 5. For EXCITEID, click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select darea from the list of load collectors (created in the last section to define the forces on the top surface of the bracket). 7. Click OK to complete the selection. 8. Similarly select the tabled1 load collector for the TID field (to define the time history of the loading). The type of excitation can be an applied load (force or moment), an enforced displacement, velocity, or acceleration. The field [TYPE] in the TLOAD1 card image defines the type of load. The type is set to applied load by default.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter transient.

3. Set Analysis type type to Transient (modal). 4. For SPC, select spc. 5. For DLOAD, select tload1. 6. For TSTEP(TIME), select tstep. 7. For METHOD (STRUCT), select the load collector eigrl. 8. For SDAMPING (STRUCT, select the load collector tabdmp1. A subcase is created that specifies the loads, boundary conditions, and damping for modal transient dynamic analysis.

Creating Output Requests 1. From the Analysis page, click control cards. 2. In the Card Image dialog, click GLOBAL_OUTPUT_REQUEST. 3. Define the DISPLACEMENT card. a) Select DISPLACEMENT. b) Leave the field for FORMAT(1) blank. c) For FORM(1), select BOTH. d) For OPTION(1), select SID. e) Double-click the SID selector and select center. f) Click return. The center set represents the node at the center of the spider attached to the mass element, which is node 395.

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4. Define the OUTPUT card. a) Select OUTPUT. b) In the number_of_outputs= field, enter 2.

c) For KEYWORD, select H3D and HGTRANS. d) For FREQ, select ALL for both. e) For H3D KEYWORD, set the other field to blank. f) Click return. 5. Click return to exit from the dialog.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 172: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter bracket_transient_modal for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the bracket_transient_modal.fem was written. The bracket_transient_modal.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are:

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bracket_transient_modal.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. bracket_transient_modal.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. bracket_transient_modal.h3d HyperView binary results file. bracket_transient_modal.res HyperMesh binary results file. bracket_transient_modal.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results 1. From the OptiStruct panel, click HyperView to launch HyperView. 2. From the menu bar, click File > Open > Session. 3. In the Open Session File dialog, open bracket_transient_modal_tran.mvw from the directory in which the input file was run. Since the loading is applied only in the z-direction, you are interested in the z-displacement time history of node 395. Plots for the displacement results contained in the file are created. 4. On the Visualization toolbar, click

to open the Curves Attributes panel.

5. Under Curves, individually select the X Trans and Y Trans curves and click Off.

Figure 173:

The X Trans and Y Trans curves are turned off. 6. Click

to fit the y-axis (that is Z displacement) of node 395.

7. You can change the color and/or line attributes of the curve, if you wish.

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Z-displacement time history of the concentrated mass at center of spider for direct transient dynamic analysis. As can be observed from the above image, the displacements of node 395 are in the negative zdirection as the loading is in the -z direction too. The displacements eventually damp out due to the structural damping present in the model.

Figure 174:

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OS-T: 1320 Nonlinear Gap Analysis of an Airplane Wing Rib

Figure 175: Wing Rib Model

There are four shell components in the model: the mounting flange, the web, the top and bottom flanges, and the lug. Gap elements have already been defined in the model and they connect the web to the lug. Coupling forces are applied to the lug and pressure loading has been defined on the top and bottom flanges of the rib joint. The mounting flange is constrained in all degrees of freedom at the four mounting hole locations and the lug is constrained for the z-displacements and rotations to prevent rigid body motion.

Exercise 1: Linear Gap Analysis Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the rib.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The rib.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Creating a Cylindrical Coordinate System For gap elements with coincident nodes as is the case here, the gap coordinate system MUST be specified. For detailed information, refer to the Help section on CGAP. 1. In the Model Browser, right-click and select Create > System Collector. 2. For Name, enter cylindrical.

3. Click Color and select a color from the color palette. 4. In the Model Browser, hide all load collectors by right-clicking on Load Collector > Hide. 5. In the Model Browser, click the Isolate Shown icon

.

6. Expand the Component list and select the Lug component. This isolates the display of only the Lug component. 7. Click the XY Top Plane View icon

to set the model view.

8. Click Geometry > Create > Systems > Axis Direction to open the Systems panel. 9. The cyan halo around the yellow nodes button indicates that it is the current option. Select the center node on the upper lug. 10. Click origin and select the center node again. 11. Click x-axisand select any node on the circumference. 12. For xy plane, select any node on the plane of the lug, as shown in Figure 176:

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Figure 176: Nodes to Select for Creating Cylindrical Coordinate System

13. Click the switch beside rectangular and select cylindrical. 14. Click create. For cylindrical systems, the x-axis defines the radial direction (q= 0) and the xy plane defines the r-q plane. 15. Repeat this process for the bottom lug (steps 9 through 12 of this sequence). 16. Click return. 17. Click on the Model Browser. 18. Select only the gap component. With Isolate Shown still active this displays only the gap component. 19. Click the Card Editor icon

.

20. Click the entity selection switch on the top left of the panel and select elems. 21. Click elems >> by window from the pop-up menu. 22. Select the gap elements that are connected to the top lug, as shown in Figure 177.

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Figure 177: Gap Elements Connected to Top Lug

23. Click select entities. 24. Click config= and select gap from the pop-up menu. 25. Click edit. 26. Click CID, and select the system that was created at the center of the top lug, as shown below.

Figure 178:

27. Click return twice to go back to the main menu. 28. Repeat this process for the gap elements that are connected to the bottom lug. The gap elements have now been assigned with a cylindrical coordinate system.

Defining a Property and Assigning it to the Gap Elements

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1. In the Model Browser, right-click and select Create > Property. 2. For Name, enter gap_prop.

3. Click Color and select a color from the color palette. 4. For Card Image, select PGAP and click Yes to confirm. 5. Make sure the check box next to U0_opts is checked. This way the initial gap opening is calculated automatically. 6. Make sure the check box next to KA_opts is checked. This determines the value of KA for each gap element using the stiffness of surrounding elements automatically.

Figure 179:

7. Click Mesh > Create > 1D Elements > Gaps to open the Gaps panel. 8. Select the update subpanel. 9. Click elems >> by collector. 10. Select gap by checking the box beside it. 11. Click the green select button. 12. Click property= and click on gap_prop. 13. Click update.

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14. Check beside property. 15. Click update. The gap elements have now been updated to the new property collector. 16. Click return.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 180: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rib_linear for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the rib_linear.fem was written. The rib_linear.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: rib_linear.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. rib_linear.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run,

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information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. rib_linear.h3d HyperView binary results file. rib_linear.res HyperMesh binary results file. rib_linear.stat Summary, providing CPU information for each step during analysis process.

Post-processing the Results 1. From the OptiStruct panel, click HyperView. This will launch HyperView and load the rib_linear.mvw file, reading the model and results. 2. Click the Curves Attributes icon

and hide all components except the Web component.

a) Activate the Auto apply mode check box b) Click on the components to turn off in the modeling window

Figure 181:

3. Go to the Contour panel

.

4. Select the first pull-down menu below Result type and select Element Stresses (2D & 3D). 5. Select the second pull-down menu below Result type and select vonMises. 6. Above the Results Browser in the left hand panel are the Load Case and Simulation Selection drop-down menus. Select Subcase 1 (Coup_Vert) from the Load Case drop-down menu.

Figure 182:

7. Click the XY Top Plane View icon

to display a top view of the Web.

8. Click Apply. This should show the contour of stresses on the Web component under the coupled loading.

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Figure 183: Stress Results on the Web From Linear Gap Analysis

9. Click Delete Page

to end the HyperView session.

Exercise 2: Nonlinear Gap Analysis Creating a Load Collector Defining Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter nonlinear.

3. Click Color and select a color from the color palette. 4. For Card Image, select NLPARM from the menu. 5. Click NINC and enter 10.

NINC denotes the number of load sub-increments. If NINC is blank, then the entire loading is applied at once. An NINC of 10 signifies that the load will be sub-divided into 10 equal increments.

6. Click MAXITER and leave the default value of 25. 7. The error tolerances EPSU, EPSP, and EPSW can be left at their default values. For details on these tolerances, read the section Nonlinear Quasi-static Gap and Contact Analysis in the online help.

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Figure 184:

Updating the Load Steps 1. Open the Load Step folder in the Model Browser. 2. Click the Coup_Vert load step to open the Entity Editor. 3. For NLPARM, click Unspecified > Loadcol. 4. In the Select Loadcol dialog, select the nonlinear load collector and click OK.

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Figure 185:

5. Repeat this process for the Pressure load step.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 186: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rib_nonlinear for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save.

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The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the rib_nonlinear.fem was written. The rib_nonlinear.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: rib_nonlinear.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. rib_nonlinear.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. rib_nonlinear.h3d HyperView binary results file. rib_nonlinear.res HyperMesh binary results file. rib_nonlinear.stat Summary, providing CPU information for each step during analysis process.

Post-processing the Results 1. From the OptiStruct panel, click HyperView. This will launch HyperView and load the rib_nonlinear.h3d file, reading the model and results. 2. Click the Curves Attributes icon

and hide all components except the Web component.

a) Activate the Auto apply mode check box b) Click on the components to turn off in the modeling window

Figure 187:

3. Go to the Contour panel

.

4. Select the first pull-down menu below Result type and select Element Stresses (2D & 3D). 5. Select the second pull-down menu below Result type and select vonMises.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 6. Above the Results Browser in the left hand panel are the Load Case and Simulation Selection drop-down menus. Select Subcase 1 (Coup_Vert) from the Load Case drop-down menu.

Figure 188:

7. Click the XY Top Plane View icon

to display a top view of the Web.

8. Click Apply. This should show the contour of stresses on the Web component under the coupled loading.

Figure 189: Stress Results on the Web From Nonlinear Gap Analysis

9. Click Delete Page

to end the HyperView session.

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Analysis Review Even though the deformation patterns are similar for both linear and nonlinear analyses, the stress patterns differ. Though the horizontal loads are in opposing directions in the lug, the stress distribution in the web for the linear run are the same around both the lug holes which is not correct. This happens as all the gaps are in a closed condition for the linear analysis. Nonlinear gap analysis gives more accurate representation. The gap status, open or closed, depending on loading condition can also be observed from the .out file: ITERATION 0 NONLINEAR

ITERATION

SUMMARY

Subcase

1

LOAD FACTOR: 0.1000 -------------------------------------------------------------Nonlinear Error Measures Gap Elem Status ITER EUI EPI EWI Open Closed -------------------------------------------------------------1 9.9000E+01 1.1659E+00 1.1659E+00 23 25 2 2.9097E-02 2.5218E+02 1.1274E+01 23 25 3 8.4208E-05 1.9063E+01 1.9427E-02 22 26 4 1.4632E-06 0.0000E+00 0.0000E+00 22 26

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OS-T: 1325 Random Response Analysis of a Flat Plate This tutorial demonstrates how to set up the random response analysis for the existing frequency response analysis model. The setup for frequency response analysis is that the flat plate has two loading conditions that will be subjected to a frequency-varying load excitation using the direct method. The PSD (power spectral density) for displacement at node 19 is output in the .rand file, and the peak values of PSD and RMS (root mean square) results are output to a .peak file. PSD and RMS stress results are output to a .op2 file and post-processed in HyperView.

Figure 190:

The frequency analysis setup is already made for this model where the one end of plate is clamped and the loading is applied on the other end (two different sources of the loading, thus two subcases). The loading frequency is defined by the FREQ1 card; from 20 to 1000 Hz with an interval of 20. The same loading frequency is applied on both the subcases.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the direct_psd.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The direct_psd.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Load Collectors In this step, two PSDF of individual subcases and one coupled PSDF (meaning that those two subcases are correlated) are defined through RANDPS Bulk Data Entry. RANDPS points to the table entity, TABRNDi. 1. Create the tabrnd1 load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter tabrnd1.

c) Click Color and select a color from the color palette. d) For Card Image, select TABRND1. e) For TABRND1_NUM, enter 4. f) For data x:, click

.

g) In the TABRND1_NUM= dialog, input the parameters as shown in Figure 191 and click Close.

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Figure 191:

2. Create the randps load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter randps.

c) Click Color and select a color from the color palette. d) For Card Image, select RANDPS. e) For NUMBER_OF_RANDPS=, enter 3 to define three RANDPS entires. f) For Data: SID, click

.

g) In the NUMBER_OF_RANDPS= dialog, input the parameters as shown in Figure 192 and click Close. The TABRND1 load collector is selected for the TID(i) column entries.

Figure 192:

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Adding Control Cards and Output Requests The RANDOM Subcase Information Entry needs to be added to the frequency analysis model and the output commands for RMS and PSD results will be added as well. 1. From the Analysis page, click control cards. 2. Go to the GLOBAL_CASE_CONTROL panel. 3. Check the box in front of RANDOM, double-click the highlighted ID button and select randps. 4. Return to Control Cards and click GLOBAL_OUTPUT_REQUEST. 5. Check the box for STRESS to activate the card edit panel. 6. Select OUTPUT2 as the FORMAT, PSDF under RANDOM, and YES under OPTION. RMS and PSDF stress are output to a .op2 file. 7. Click return to go back to the Control Cards panel.

8. Select CASE_UNSUPPORTED_CARDS and add the following cards: XYPLOT,DISP,PSDF/ 19(T3) OptiStruct will output the PSDF for the translational displacement in z direction at node 19. 9. Click OK, and then click return.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 193: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter direct_psd for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the direct_psd.fem was written. The direct_psd.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: direct_psd.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. direct_psd.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. direct_psd.h3d HyperView binary results file. direct_psd.res HyperMesh binary results file. direct_psd.stat Summary, providing CPU information for each step during analysis process. Also, the following files will be output and which are specific to the random response analysis. direct_psd.peak ASCII result file, containing RMS and peak values of PSD. direct_psd.rand ASCII result file, containing PSD results. direct_psd.mvw HyperView script file. This file will automatically create the plot of PSD over the frequency for the results contained in .rand file. direct_psd.op2 Binary file containing RMS and PSD results.

Viewing the Results This step describes how to post-process the RMS and PSD results in HyperView. The PSD for displacement at node 19 is output to direct_psd.rand file and the plot of PSD vs. frequency can be viewed by loading the direct_psd_rand.mvw file. The RMS and PSD stress results are available in .op2 file. The RMS and the peak values of PSD for displacement at node 19 are output to .peak file, which can be reviewed with any text editor. 1. Open a HyperView session.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 2. Load the Direct_psd.op2 file. 3. Go to Contour panel.

4. In the Load Case and Simulation Selection window, select the random subcase and the frequency = 20.0 Hz as the Simulation. 5. Select result type PSD STRESS (t), vonMises, and click Apply. The PSD vonMises stress contour at frequency 20.0 Hz are displayed as below:

Figure 194:

6. Change the Simulation to Simulation 1. 7. Select the result type RMS stress, vonMises, and click Apply. The RMS stress contour is displayed. 8. In the HyperView window, click File > Open > Sessions. The Open Session File window opens. 9. Select the directory where the job was run and select the file direct_psd_rand.mvw. 10. Click Open.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

Figure 195:

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OS-T: 1330 Acoustic Analysis of a Half Car Model The purpose of this tutorial is to evaluate the vibration characteristics of a half car model subjected to Fluid - Structure interaction. The fluid that is being referred to is air. Essentially, the noise level or the sound level is evaluated inside the car at a location near the ear of the driver which is the main response location inside the fluid.

Figure 196: Half Car Model

The half car model is excited at the bottom of the car, as shown by a red constraint symbol (triangle) in Figure 196. The excitation provided is with the application of a unit load along the direction of the height of the car (Z-axis).

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the Half_Car.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Half_Car.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Materials and Properties and Assigning to Structural and Fluid Elements 1. In the Model Browser, right-click and select Create > Material. 2. For Name, enter MAT1_shells.

3. For Card Image, select MAT1 from the drop-down menu. 4. Fill in the fields for E, Nu and Rho respectively as 2.1e04, 0.33 and 8.0e-10.

Figure 197:

5. In the Model Browser, right-click and select Create > Material. 6. For Name, enter MAT10_Solids.

7. For Card Image, select MAT10 from the drop-down list.

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8. Fill in the fields for Rho and C respectively as 1.2e-13 and 3.4e5. 9. In the Model Browser, right-click and select Create > Property. 10. For Name, enter Shells.

11. For Card Image, select PSHELL from the drop-down menu. 12. For Material, click Unspecified > Material. 13. In the Select Material dialog, select MAT1_shells from the list of materials and click OK to complete the selection. 14. Enter the thickness for the shell component by clicking T, and entering 2.0. 15. In the Model Browser, right-click and select Create > Property. 16. For Name, enter Solids.

17. For Card Image, select PSOLID from the drop-down menu. 18. For Material, click Unspecified > Material. 19. In the Select Material dialog, select MAT10_Solids. 20. For FCTN, select PFLUID. 21. Click on the fluid component. The component entry is displayed in the Entity Editor. 22. For Property, click Unspecified > Property. 23. In the Select Property dialog, select the property solids. 24. Click on the structure component. The component entry is displayed in the Entity Editor. 25. For Property, click Unspecified > Property. 26. In the Select Property dialog, select the property shells.

Creating Load Collectors In this step the model is unconstrained and a unit vertical load is applied acting upwards in the positive z-direction at a point on the base of the car (shown in page 1). The model can be unconstrained as the solver applies PARAM, INREL -2 by default to avoid the model from experiencing a rigid body motion. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter unit-load.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. 5. Verify unit_load is the current load collector. If it is not the current load collector, right-click on unit_load in the Model Browser and select Make Current from the context menu. Tip: In the Model Browser, Load Collectors folder, the current load collector is bold.

Creating a Unit Load at a Point

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 1. From the Analysis page, click constraints. 2. Select the create subpanel using the radio buttons on the left-hand side of the panel. 3. Select node number 19072 on the car model by clicking nodes >> by id. 4. Uncheck all dofs, except dof3. 5. Click the = to the right of dof3 and enter a value of 1.

6. For Load Types =, select DAREA from the extended entity selection menu. 7. Click create. This applies a unit load to the selected node.

Figure 198:

8. Click return.

Creating a Frequency Range Table 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLED1 from the drop-down menu. 5. For TABLED1_NUM, input a value of 2 and press Enter. 6. Click the Table icon

below TABLED1_NUM and enter x(1) = 0.0, y(1) = 1.0, x(2) =

1000.0200.0 and y(2) = 1.0 in the pop-out window.

7. Click Close. This provides a frequency range of 0.0 to 1000.0200 with a constant 1.0 over this range.

Creating a Frequency Dependent Dynamic Load 1. In the Model Browser, right-click and select Create > Load Collector.

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2. For Name, enter rload1.

3. Click Color and select a color from the color palette. 4. For Card Image, select RLOAD1 from the drop-down menu. 5. For EXCITEID, click Unspecified > Loadcol. 6. In the Select Loadcol dialog, select unit-load from the list of load collectors and click OK to complete the selection. 7. Similarly select the load collector tabled1 for the TC field. The type of excitation can be an applied load (force or moment), an enforced displacement, velocity, or acceleration. The field TYPE in the RLOAD1 card image defines the type of load. The type is set to applied load by default. A typical RLOAD1 card appears, as shown below.

Figure 199:

8. In the Model Browser, right-click and select Create > Load Collector. 9. For Name, enter freq1.

10. Click Color and select a color from the color palette. 11. For Card Image, select FREQi from the drop-down menu. 12. Check the box next to FREQ1. 13. For NUMBER_OF_FREQ1, enter a value of 1, press ENTER. 14. Click

next to the Data field and enter, F1= 0.0, DF= 1.0, and NDF= 200.

This provides a set of frequencies beginning with 0.0, incremented by 1.0 and 200 frequencies increments and the card appears as shown below on the GUI.

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Figure 200:

15. In the Model Browser, right-click and select Create > Load Collector. 16. For Name, enter eigrl1.

17. Click Color and select a color from the color palette. 18. For Card Image, select EIGRL from the drop-down menu. 19. For V2, enter a value of 600.0. 20. For ND, enter a value of 50.

This specifies a range of frequency between an initial frequency and 600 Hz for eigenvalue extraction using the Lanczos method. 21. Similarly, follow steps 8.1 to 8.6 to create another load collector named eigrl2.

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Figure 201:

22. In the Model Browser, right-click and select Create > Load Step. 23. For Name, enter subcase1.

24. Click Color and select a color from the color palette. 25. For Analysis type, select Freq.resp (modal) from the drop-down menu. 26. For METHOD(STRUCT), select eigrl1 from the list of load collectors. 27. For METHOD(FLUID), select eigrl2 from the list of load collectors. 28. For DLOAD, select rload1 from the list of load collectors. 29. For FREQ, select freq1 from the list of load collectors. An OptiStruct subcase has been created which references the constraints, the unit load in the load collector rload1 with a set of frequencies defined in load collector freq1 and modal method defined in the load collector eigrl. 30. In the Model Browser, right-click and select Create > Set. 31. For Name, enter SETA.

32. For Card Image, select None from the drop-down menu. 33. Leave the Set Type switch set to non-ordered type. 34. For Entity IDs, click the yellow Nodes panel and select nodes with ID 18881. 35. Click proceed.

Creating a Set of Frequencies

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1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter freq1.

3. Click Color and select a color from the color palette. 4. For Card Image, select FREQi from the drop-down menu. 5. Check the FREQ1 option and enter 1 in the NUMBER_OF_FREQ1 field. 6. Click

and enter information in the pop-out window.

a) For F1, enter 0.0. b) For DF, enter 1.0.

c) For NDF, enter 200.

7. Click Close. This provides a set of frequencies beginning with 0.0, incremented by 1.0 and 200 frequencies increments and the card appears as shown below on the GUI.

Creating the Modal Method for Eigenvalue Analysis 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter eigrl1.

3. Click Color and select a color from the color palette. 4. For Card Image, select EIGRL from the drop-down menu. 5. For V2, enter a value of 600.0. 6. For ND, enter a value of 50.

This specifies a range of frequency between an initial frequency and 600 Hz for eigenvalue extraction using the Lanczos method. 7. Similarly, create another load collector named eigrl2.

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Figure 202:

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step. A default load step template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter subcase1.

3. For Analysis type, select Freq.resp (modal) from the drop-down menu. 4. For METHOD(STRUCT), select eigrl1. 5. For METHOD(FLUID), select eigrl2 from the list of load collectors.

Creating a Set of Nodes 1. In the Model Browser, right-click and select Create > Set. 2. For Name, enter SETA.

3. For Card Image, select None. 4. Leave the Set Type switch set to non-ordered type. 5. For Entity IDs, select Nodes from the selection switch. 6. Click Nodes and select nodes 18881. 7. Click proceed.

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Creating a Set of Outputs 1. From the Analysis page, click control cards. 2. Click on ACMODL. This defines the model parameters for fluid-structure interface. 3. Click [INTER] and select DIFF. 4. Click [INFOR] and select ALL. 5. Click return to exit this menu. 6. Select GLOBAL_OUTPUT_REQUEST. Then check the box to the left of DISPLACEMENT. A new window appears in the work area screen. 7. Click the field box FORM and select PHASE from the pop-up menu. 8. Click the field box OPTION and select SID from the pop-up menu. A new field appears in yellow. 9. Double-click the yellow SID box and select SETA from the pop-up selection on the bottom left corner. A value of 1 now appears below the SID field box. This sets the output for only the nodes in set 1. 10. Click return to exit this menu. 11. Select GLOBAL_CASE_CONTROL. 12. Check the box next to FREQ. 13. Click FREQ and select the load collector freq1. 14. Click return to exit this menu and click next. 15. Select the OUTPUT subpanel. A new window appears in the work area. 16. Specify number of outputs = 4.

17. Verify KEYWORD is set to HGFREQ. Using HGFREQ results in a frequency output presentation for HyperGraph. 18. Double-click on the box beneath FREQ and select ALL from the pop-up selection. Choosing ALL outputs results for all frequencies. 19. Verify KEYWORD is set to OPTI. 20. Double-click on the box beneath FREQ and select ALL from the pop-up selection. 21. Similarly under KEYWORD select PUNCH and H3D. 22. Click return to exit this menu. 23. Select PARAM. 24. Click AUTOSPC. 25. Scroll down and check the box next to G. A new window appears in the work area screen. 26. Click below G_V1, and input a value of 0.06 into the field box.

This value specifies a uniform structural damping coefficient and is obtained by multiplying the critical damping [C/C0] ratio by 2.0.

27. Check the box next to GFL.

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28. Click below [VALUE] and enter 0.12.

29. Click return to exit the PARAM menu. 30. Click return to exit the control cards menu.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 203: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Half_car for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the Half_car.fem was written. The Half_car.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: Half_car.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. Half_car.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run,

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information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. Half_car.h3d HyperView binary results file. Half_car.res HyperMesh binary results file. Half_car.stat Summary, providing CPU information for each step during analysis process.

Reviewing the Results This step describes how to view displacement results (.mvw file) in HyperGraph. The HyperView results file (.h3d) contains only the displacement results for the node specified in the node set output. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. In the HyperView window, click File > Open > Session. An Open Session File window opens. 4. Select the directory where the job was run and select the file Half_car.mvw. 5. Click Open. A discard warning appears.

6. Click Yes. Two graphs per page and a total of one page are displayed in HyperGraph. The graph title shows Subcase 1 (subcase 1) pressure at grid 18881. 7. Click the Axis toolbar icon

.

8. Make sure the Axis is set to Primary and Horizontal. 9. Click the Scale and Tics tab. 10. Make sure the toggle is set to Linear.

Figure 204:

11. In the Axis, toggle from Horizontal to Vertical.

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12. Click on the Scale and Tics (Magnitude) tab. 13. Make sure the toggle is set to dB10.

Figure 205:

There are two sets of results on this page. The top graph shows Phase Angle verses Frequency (log). The bottom graph shows Magnitude verses Frequency (log) (see figure below) for Pressure at grid 18881.

Figure 206:

This concludes the HyperGraph results processing.

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OS-T: 1340 Fatigue (Stress - Life) Method Fatigue using S-N (Stress - Life) Method OptiStruct uses the S-N approach for calculating the fatigue life. The S-N approach is suitable for high cycle fatigue, where the material is subject to cyclical stresses that are predominantly within the elastic range. Structures under such stress ranges should typically survive more than 1000 cycles. The S-N approach is based on elastic cyclic loading, inferring that the S-N curve should be confined to numbers greater than 1000 cycles. This ensures that no significant plasticity is occurring. This is commonly referred to as high-cycle fatigue.

Figure 207: Low Cycle and High Cycle regions on the S-N curve

Since S-N theory deals with uniaxial stress, the stress components need to be resolved into one combined value for each calculation point, at each time step, and then used as equivalent nominal stress applied on the S-N curve. In OptiStruct, various stress combination types are available with the default being "Absolute maximum principle stress". In general "Absolute maximum principle stress" is recommended for brittle materials, while "Signed von Mises stress" is recommended for ductile material. The sign on the signed parameters is taken from the sign of the Maximum Absolute Principal value.

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Figure 208: Fatigue Analysis Flowchart

The three aspects to the fatigue definition are the fatigue material properties, the fatigue parameters and the loading sequence and event definitions.

Fatigue Material Properties (S-N Curve)

Figure 209: Two Segment S-N Curve

FATDEF

Defines the elements and associated fatigue properties that will be used for the fatigue analysis.

PFAT

Defines the finish, treatment, layer and the fatigue strength reduction factors for the elements.

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Defines the material properties for the fatigue analysis. These properties should be obtained from the material's S-N curve (Figure 209). The S-N curve, typically, is obtained from completely reversed bending on mirror polished specimen. S-N curves can be one segment or two segments.

Fatigue Parameters

Figure 210: Mean Stress Correction

FATPARM

Defines the parameters for the fatigue analysis. These include stress combination method, mean stress correction method (Figure 210), Rainflow parameters, Stress Units.

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Fatigue Sequence and Event Definition

Figure 211: Load Time History

FATSEQ

Defines the loading sequence for the fatigue analysis. This card can refer to another FATSEQ card or a FATEVNT card.

FATEVNT

Defines loading events for the fatigue analysis.

FATLOAD

Defines fatigue loading parameters.

The following files found in the optistruct.zip file are needed to perform this tutorial. Refer to Accessing the Model Files. ctrlarm.fem, load1.csv and load2.csv

Exercise In this tutorial, a control arm loaded by brake force and vertical force is used, as shown in Figure 212. Two load time histories acquired for 2545 seconds with 1 HZ, shown in Figure 213, are adopted. The SN curve of the material used in the control arm is shown in Figure 215. Because a crack always initiates from the surface, a skin meshed with shell elements is designed to cover the solid elements, which can improve the accuracy of calculation as well.

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Figure 212: Model of the Control Arm for Fatigue Analysis

Figure 213: Load Time History for Vertical Force

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Figure 214: Load Time History for Braking Force

Figure 215: SN Curve

The model being used for this exercise is that of a control arm, as shown in Figure 212. Loads and boundary conditions and two static loadcases have already been defined on this model.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the ctrlarm.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Defining TABFAT Load Collector The first step in defining the loading sequence is to define the TABFAT cards. This card represents the loading history. 1. Make sure the Utility menu is selected in the View menu. Click View > Browsers > HyperMesh > Utility. 2. Click on the Utility menu beside the Model tab in the browser. In the Tools section, click on TABLE Create. 3. Set Options to Import table. 4. Set Tables to TABFAT. 5. Click Next. 6. Browse for the loading file. 7. In the Open the XY Data File dialog box, set the Files of type filter to CSV (*.csv). 8. Open the load1.csv file you saved to your working directory from the optistruct.zip file. 9. Create New Table with Name table1.

10. Click Apply to save the table. The load collector table1 with TABFAT card image is created. 11. Browse for a second loading file load2.csv. 12. Create New Table with Name table2.

13. Click Apply to save the table. The load collector table2 with TABFAT card image is created. 14. Exit from the Import TABFAT window. Tables appear under Load Collector in the Model Browser.

Note: A file in DAC format can very easily be imported in HyperGraph and converted to CSV format to be read in HyperMesh.

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Defining TABLOAD Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATLOAD1.

3. Click Color and select a color from the color palette. 4. For Card Image, select FATLOAD from the drop-down menu. 5. For TID (table ID), select table1 from the list of load collectors. 6. For LCID (load case ID), select SUBCASE1 from the list of load steps. 7. Set LDM (load magnitude) to 1. 8. Set Scale to 3.0.

9. Repeat the process to create another load collector named FATLOAD2 with FATLOAD as card image and pointing to table2 and SUBCASE2. 10. Set LDM to 1 and Scale to 3.0.

Defining TABEVNT Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATEVENT.

3. For Card Image, select FATEVNT. 4. Set FATEVNT_NUM_FLOAD to 2. 5. Click on the Table icon

next to the Data field and select FATLOAD1 for FLOAD(1) and

FATLOAD2 for FLOAD(2) in the pop-out window.

Defining TABSEQ Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATSEQ.

3. For Card Image, select FATSEQ. 4. For FID (Fatigue Event Definition), select FATEVENT from the list of load collectors. Defining the sequence of events for the fatigue analysis is completed. The Fatigue parameters are defined next.

Defining Fatigue Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter fatparam.

3. For Card Image, select FATPARM. 4. Make sure TYPE is set to SN. 5. Set STRESS COMBINE to SGVON (Signed von Mises). 6. Set STRESS CORRECTION to GERBER. 7. Set STRESSU to MPA (Stress Units).

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8. Set RAINFLOW RTYPE to LOAD. 9. Set CERTNTY SURVCERT to 0.5.

Defining Fatigue Material Properties The material curve for the fatigue analysis can be defined on the MAT1 card. 1. In the Model Browser, click on the Aluminum material. The Entity Editor opens. 2. In the Entity Editor, set SN to MATFAT. 3. Set UTS (ultimate tensile stress) to 600.

4. For the SN curve set (these values should be obtained from the material's SN curve): SRI1

1420.58

B1

-0.076

NC1

5.0e8

SE

0.1

Defining PFAT Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter pfat.

3. For Card Image, select PFAT. 4. Set LAYER to TOP. 5. Set FINISH to NONE. 6. Set TRTMENT to NONE.

Defining FATDEF Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter fatdef.

3. For Card Image, select FATDEF. 4. Check the box next to PSHELL. 5. Click

next to the Data field and select shell for PID(1), and pfat for PFATID(1) in the pop-up

window. 6. Click Close.

Defining the Fatigue Load Step 1. In the Model Browser, right-click and select Create > Load Step.

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2. For Name, enter Fatigue.

3. Set the Analysis type to fatigue. 4. For FATDEF, select fatdef. 5. For FATPARM, select fatparam. 6. For FATSEQ, select FATSEQ.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 216: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter ctrlarm_hm for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the ctrlarm_hm.fem was written. The ctrlarm_hm.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Reviewing the Results 1. When the analysis process completes, click HyperView to launch the results. 2. In the Results tab, select Subcase 3 (Fatigue) from the subcase field. 3. On the Results toolbar, click

to open the Contour panel.

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4. Set Result type to Damage and click Apply to contour the elements.

Figure 217: Elemental Damage Results

Fatigue Process Manager (FPM) using S-N (Stress - Life) Method OptiStruct uses the S-N approach for calculating the fatigue life. The S-N approach is suitable for high cycle fatigue, where the material is subject to cyclical stresses that are predominantly within the elastic range. Structures under such stress ranges should typically survive more than 1000 cycles.

Exercise The S-N approach is based on elastic cyclic loading, inferring that the S-N curve should be confined to numbers greater than 1000 cycles. This ensures that no significant plasticity is occurring. This is commonly referred to as high-cycle fatigue.

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Figure 218: Low Cycle and High Cycle Regions on the S-N Curve

Since S-N theory deals with uniaxial stress, the stress components need to be resolved into one combined value for each calculation point, at each time step, and then used as equivalent nominal stress applied on the S-N curve (Figure 219).

Figure 219: Two segment S-N Curve

In OptiStruct various stress combination types are available, with the default being "Absolute maximum principle stress". In general "Absolute maximum principle stress" is recommended for brittle materials, while "Signed von Mises stress" is recommended for ductile material. The sign on the signed parameters is taken from the sign of the Maximum Absolute Principal value. In this tutorial, you will be able to evaluate fatigue life with the S-N method through process manager step by step.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click Tools > Fatigue Process > Create New. 2. Input New Session Name and Working Folder and click Create. This creates a new file to save the instance of the currently loaded fatigue process template. When finished, the Fatigue Analysis tree will appear.

Figure 220: Launching Fatigue Process Manager (FPM)

3. Make sure the task Import File is selected in the Fatigue Analysis tree. 4. For the Model file type, select OptiStruct. 5.

Click the Open model file icon

.

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A Select File browser window opens. 6. Select the ctrlarm.fem file you saved to your working directory from the optistruct.zip file and click Open. 7. Click Import. This loads the control arm model. It includes a whole definition of two static subcases, elements sets, and material static properties, etc. 8. Click Apply. This guides you to the next task Fatigue Subcase of the Fatigue Analysis tree.

Figure 221: Import a Finite Element Model file

Setting Up the Model Creating a Fatigue Subcase 1. Make sure the task Fatigue Subcase is selected in the Fatigue Analysis tree. 2. In the Create new fatigue subcase field, enter fatsub_fpmtut. 3. Click Create.

4. For the Select existing fatigue subcase field, select the newly created fatigue subcase fatsub_fpmtut.

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fatsub_fpmtut is selected as the active fatigue subcase. Definitions in the following processes (analysis parameters, fatigue elements and properties, loading sequences, etc.) will be for this subcase. 5. Click Apply. This saves the current definitions and guides you to the next task Analysis Parameters of the Fatigue Analysis tree.

Figure 222: Create and Select Active Fatigue Subcase to Process

Applying Fatigue Analysis Parameters 1. Make sure the task Analysis Parameters is selected in the Fatigue Analysis tree. 2. Select the following options: Analysis type

S-N

Stress combination method

Signed von Mises

Mean stress correction

GERBER

FEA stress unit

MPA

Rainflow type

STRESS

3. Enter the following values:

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Gate 0.0 Certainty of survival 0.5 4. Click Apply. This saves the current definitions and guides you to the next task Elements and Materials of the Fatigue Analysis tree. For details, consult the HyperWorks 2019 help.

Figure 223: Fatigue Analysis Parameters Definition

Adding Fatigue Elements and Materials 1. Make sure the task Elements and Materials is selected in the Fatigue Analysis tree. 2. Click Add. A Material Data window opens. 3. For Element entity type, select Property - PSHELL. 4. For Element entity name, select shell. This is the skin coating the solid control arm. 5. Make sure Ultimate tensile strength (UTS) is selected to define the material data. 6. For UTS, enter the value 600.

7. For Input method of defining S-N curve, select Estimate From UTS.

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.

An SN method description window introducing how to generate the SN material parameter opens. 9. Click Close. 10. For Material type, select Aluminum Alloys and click Estimate. All the data for SN curve definition are automatically estimated. 11. Click Plot SN Curve at the bottom of the window to show the SN curve. 12. Close the SN Curve plot window. 13. For Layer of stress results in shell elements, select TOP. 14. For Surface finish, select No Finish. 15. For Surface treatment, select No Treatment. 16. Leave the field after Fatigue strength reduction factor blank. 17. Click Save to save the definition of the SN data for the selected elements. 18. Click Apply. This saves the current definitions and guides you to the next task Load-Time History of the Fatigue Analysis tree.

Figure 224: Material Data Definition

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Figure 225: Elements and Material Definition

Applying Load-Time History 1. Make sure the task Load-Time History is selected in the Fatigue Analysis tree. 2. Click Add by File. A Load Time History window opens. 3. For Load-time history name, enter lth1. 4. For Load-time history type, select CSV. 5.

Click the Open load-time file icon An Open file browser window opens.

.

6. Browse for load1.csv. 7. Click Open > Import.

8. Click Save to write the new load-time history into HyperMesh database. 9. Create another load-time history lth2 by importing the file load2.csv. 10. Click Plot L-T to show the load-time history. 11. Close the Load Time History window. 12. Click Apply. This saves the current definitions and guides you to the next task Loading Sequences of the Fatigue Analysis tree.

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Figure 226: Load-Time History Definition

Figure 227: Import Load-Time History

Note: For a file of DAC format, it can very easily be imported in HyperGraph and converted to CSV format for use by FPM.

Loading Sequences In this step, one event consisting of two load time history is created; in other words, the linear superposition of the stress caused by the two load time history is requested during analysis. Using this event, one load sequence is constructed. 1. Make sure the task Loading Sequences is selected in the Fatigue Analysis tree.

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2. Click Add. A Loading Definition window opens. 3. For Select static loadcase, select SUBCASE1. 4. For Select load-time history, select lth1. 5. For Scale, enter the value 3.0.

6. Make sure Create new is selected using the radio buttons. 7. Enter Event1 for the newly created fatigue event name.

Figure 228: Associate Load-Time History with Static Subcase

8. Click Save > Add. A Loading Definition window opens. 9. For Select static loadcase, select SUBCASE2. 10. For Select load-time history, select lth2. 11. Enter the value 3.0 for Scale.

12. Make sure Existing is selected using the radio buttons. For Existing, select Event1. 13. Click Save > Apply. This saves the current definitions and guides you to the next task Submit analysis of the Fatigue Analysis tree.

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Figure 229: Loading Sequences Definition

Submitting the Job 1. Make sure the task Submit Analysis is selected in the Fatigue Analysis tree. 2.

Click the Save .fem file icon . A Save As browser window opens.

3. Set the directory in which to save the file, and for File name, enter ctrlarm_fpmtut.fem. 4. Click Save to close the window.

5. Click Save to save the OptiStruct model file. 6. For Run Option, select analysis. 7. Click Submit. This launches OptiStruct 2019 to run the fatigue analysis. If the job is successful, the new results files should be in the directory from which ctrlarm_fpmtut.fem was selected. The default files written to the directory are:

ctrlarm_fpmtut.0.3.fat

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An ASCII format file which contains fatigue results of each fatigue subcase in iteration step.

OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

ctrlarm_fpmtut.h3d

Hyper 3D binary results file, with both static analysis results and fatigue analysis results.

ctrlarm_fpmtut.out

OptiStruct output file containing specific information on the file set up, the set up of your fatigue problem, compute time information, etc. Review this file for warnings and errors.

ctrlarm_fpmtut.stat

Summary of analysis process, providing CPU information for each step during analysis process.

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Figure 230: Submit Fatigue Analysis

Post-processing the Analysis 1. Make sure the task Post-processing is selected in the Fatigue Analysis tree. When fatigue analysis has completed successfully after the previous submit, it will automatically go into this task. 2. Click View and select the Results type Life.

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3. Check the top 0.1%, 1.0%, 5.0% average life, and Top 1, 2, 3 most damage elements lives. 4. Toggle the Result type to view the damage results summary. 5. Click Load H3D Results (HV). This launches HyperView to load the ctrlarm_fpmtut.h3d results file for more detailed results. 6. Click Close to unload Fatigue Process Manager.

Figure 231: Life Results Summary

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Figure 232: Damage Contour in HyperView

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OS-T: 1350 Fatigue (Strain - Life) Method Fatigue using E-N (Strain - Life) Method The E-N (Strain - Life) method should be chosen to predict the fatigue life when plastic strain occurs under the given cyclic loading. S-N (Stress - Life) method is not suitable for low-cycle fatigue where plastic strain plays a central role for fatigue behavior. If an S-N analysis indicates a fatigue life less than 10,000 cycles, it is a sign that an E-N method may be a better choice. The E-N method, while computationally more expensive than S-N, should give a reasonable estimate for high-cycle fatigue as well.

Figure 233: Low Cycle and High Cycle Regions on the S-N Curve

Since E-N theory deals with uniaxial strain, the strain components need to be resolved into one combined value for each calculation point, at each time step, and then used as equivalent nominal strain applied on the E-N curve (Figure 234).

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Figure 234: Strain-Life Curve

In OptiStruct various strain combination types are available with the default being "Absolute maximum principle strain". In general "Absolute maximum principle stain" is recommended for brittle materials, while "Signed von Mises strain" is recommended for ductile material. The sign on the signed parameters is taken from the sign of the Maximum Absolute Principal value.

Figure 235: Fatigue Analysis Flowchart

The three aspects to the fatigue definition are the fatigue material properties, the fatigue parameters and the loading sequence and event definitions.

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FATDEF

Defines the elements and associated fatigue properties that will be used for the fatigue analysis.

PFAT

Defines the finish, treatment, layer and the fatigue strength reduction factors for the elements.

MATFAT

Defines the material properties for the fatigue analysis. These properties should be obtained from the material's E-N curve (Figure 234). The E-N curve, typically, is obtained from completely reversed bending on mirror polished specimen.

Fatigue Parameters

Figure 236: Mean Stress Correction

FATPARM

Defines the parameters for the fatigue analysis. These include stress combination method, mean stress correction method (Figure 236), Rainflow parameters, and Stress Units.

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Fatigue Sequence and Event Definition

Figure 237: Load Time History

FATSEQ

Defines the loading sequence for the fatigue analysis. This card can refer to another FATSEQ card or a FATEVNT card.

FATEVNT

Defines loading events for the fatigue analysis.

FATLOAD

Defines fatigue loading parameters.

TABLEFAT

Defines the y values for each point on the time loading history (Figure 237).

Exercise In this tutorial, a control arm loaded by brake force and vertical force is used, as shown in Figure 238. Two load time histories acquired for 2545 seconds with 1 HZ, shown in Figure 239 and Figure 240, are adopted. The material of the control arm is aluminum, whose E-N curve is shown in Figure 241. Because a crack always initiates from the surface, a skin meshed with shell elements is designed to cover the solid elements, which can improve the accuracy of calculation as well.

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Figure 238: Model of the Control Arm for Fatigue Analysis

Figure 239: Load Time History for Vertical Force

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Figure 240: Load Time History for Braking Force

Figure 241: EN Curve of Aluminum

The model being used for this exercise is that of a control arm as shown in Figure 238. Loads and boundary conditions and two static loadcases have already been defined on this model.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the ctrlarm.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Defining TABFAT Load Collector The first step in defining the loading sequence is to define the TABFAT cards. This card represents the loading history. 1. Make sure the Utility menu is selected in the View menu. Click View > Browsers > HyperMesh > Utility. 2. Click on the Utility menu beside the Model tab in the browser. In the Tools section, click on TABLE Create. 3. Set Options to Import table. 4. Set Tables to TABFAT. 5. Click Next. 6. Browse for the loading file. 7. In the Open the XY Data File dialog box, set the Files of type filter to CSV (*.csv). 8. Open the load1.csv file you saved to your working directory from the optistruct.zip file. 9. Create New Table with Name table1.

10. Click Apply to save the table. The load collector table1 with TABFAT card image is created. 11. Browse for a second loading file load2.csv. 12. Create New Table with Name table2.

13. Click Apply to save the table. The load collector table2 with TABFAT card image is created. 14. Exit from the Import TABFAT window. Tables appear under Load Collector in the Model Browser.

Note: A file in DAC format can very easily be imported in HyperGraph and converted to CSV format to be read in HyperMesh.

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Defining FATLOAD Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATLOAD1.

3. For Card Image, select FATLOAD. 4. For TID(table ID), select table1 from the list of load collectors. 5. For LCID(load case ID), select SUBCASE1 from the list of load steps. 6. Set LDM(load magnitude) to 1. 7. Set Scale to 5.0.

8. Repeat the process to create another load collector named FATLOAD2 with FATLOAD card image and pointing to table2 and SUBCASE2. 9. Set LDM to 1 and Scale to 5.0.

Defining TABEVNT Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATEVENT.

3. For Card Image, select FATEVNT. 4. Set FATEVNT_NUM_FLOAD to 2. 5. Click on the Table icon

next to the Data field and select FATLOAD1 for FLOAD(1) and

FATLOAD2 for FLOAD(2) in the pop-out window.

Defining TABSEQ Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter FATSEQ.

3. For Card Image, select FATSEQ. 4. For FID (Fatigue Event Definition), select FATEVENT from the list of load collectors. Defining the sequence of events for the fatigue analysis is completed. The Fatigue parameters are defined next.

Defining Fatigue Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter fatparam.

3. For Card Image, select FATPARM. 4. Make sure TYPE is set to EN. 5. Set STRESS COMBINE to SGVON (Signed von Mises). 6. Set STRESS CORRECTION to SWT. 7. Set STRESSU to MPA (Stress Units). 8. Set PLASTI to NEUBER (plasticity correction).

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 9. Set RAINFLOW RTYPE to STRESS. 10. Set CERTNTY SURVCERT to 0.5.

Defining the Fatigue Material Properties The material curve for the fatigue analysis can be defined on the MAT1 card. 1. In the Model Browser, click on the Aluminum material. The Entity Editor opens. 2. In the Entity Editor, set MATFAT as EN from the list. 3. Set UTS (ultimate tensile stress) to 600.

4. For the EN curve set (these values should be obtained from the material's EN curve). SF

1002.000

B

-0.095

C

-0.690

EF

0.350

NP

0.110

KP

966.000

NC

2E+08

SEE

0.100

SEP

0.100

Defining PFAT Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter pfat.

3. For Card Image, select PFAT. 4. Set LAYER to TOP. 5. Set FINISH to NONE. 6. Set TRTMENT to NONE.

Defining the FATDEF Card 1. In the Model Browser, click on the Create > Load Collector material. 2. For Name, enter fatdef.

3. Set the Card Image to FATDEF.

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4. Activate PSHELL in the Entity Editor. 5. Click the Data:PID, PFATID option to open the dialog. 6. For PID(1), select shell. 7. For PFATID(1), select pfat.

Defining the Fatigue Load Case 1. In the Model Browser, click on Create > Load Step 2. For Name, enter Fatigue.

3. Set the Analysis type to Fatigue. 4. For FATDEF, select fatdef. 5. For FATPARM, select fatparam. 6. For FATSEQ, select FATSEQ.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 242: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job.

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If the job is successful, new results files should be in the directory where the .fem was written. The .out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Reviewing the Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Go to the Results tab. 3. Change the Load Case to Subcase 3 - fatigue. 4. On the Results toolbar, click

to open the Contour panel.

5. Set Result type to Damage and click on Apply to contour the elements.

Figure 243: Elemental Damage Results

Fatigue Process Manager (FPM) using E-N (Strain - Life) Method The E-N (Strain - Life) method should be chosen to predict the fatigue life when plastic strain occurs under the given cyclic loading. S-N (Stress - Life) method is not suitable for low-cycle fatigue where plastic strain plays a central role for fatigue behavior. If an S-N analysis indicates a fatigue life less than 10,000 cycles, it is a sign that E-N method might be a better choice. E-N method, while computationally more expensive than S-N, should give reasonable estimate for high-cycle fatigue as well.

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Figure 244: Low Cycle and High Cycle regions on the S-N curve

Since E-N theory deals with uniaxial strain, the strain components need to be resolved into one combined value for each calculation point, at each time step, and then used as equivalent nominal strain applied on the E-N curve (Figure 245).

Figure 245: Strain-Life Curve

In OptiStruct, various strain combination types are available with the default being "Absolute maximum principle strain". In general "Absolute maximum principle stain" is recommended for brittle materials, while "Signed von Mises strain" is recommended for ductile material. The sign on the signed parameters is taken from the sign of the Maximum Absolute Principal value. In this tutorial, you will be able to evaluate fatigue life with the E-N method.

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The following files found in the optistruct.zip file are needed to perform this tutorial. Refer to Accessing the Model Files.

Exercise A control arm loaded by brake force and vertical force is used, as shown in Figure 246. Two load time histories acquired for 2545 seconds with 1 HZ, shown in Figure 247 and Figure 248, are applied. The material of the control arm is aluminum, whose E-N curve is shown in Figure 249. Because a crack always initiates from the surface, a skin meshed with shell elements is designed to cover the solid elements, which can improve the accuracy of calculation as well.

Figure 246: Model of Control Arm for Fatigue Analysis

Figure 247: Load Time History for Vertical Force

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Figure 248: Load Time History for Braking Force

Figure 249: E-N Curve of Aluminum

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model

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1. Click Tools > Fatigue Process > Create New. 2. Input New Session Name and Working Folder and click Create. This creates a new file to save the instance of the currently loaded fatigue process template. When finished, the Fatigue Analysis tree will appear.

Figure 250: Launching Fatigue Process Manager (FPM)

3. Make sure the task Import File is selected in the Fatigue Analysis tree. 4. For the Model file type, select OptiStruct. 5.

Click the Open model file icon . A Select File browser window opens.

6. Select the ctrlarm.fem file you saved to your working directory from the optistruct.zip file and click Open. 7. Click Import. This loads the control arm model. It includes a whole definition of two static subcases, elements sets, and material static properties, etc. 8. Click Apply. This guides you to the next task Fatigue Subcase of the Fatigue Analysis tree.

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Figure 251: Import a Finite Element Model file

Setting Up the Model Creating a Fatigue Subcase 1. Make sure the task Fatigue Subcase is selected in the Fatigue Analysis tree. 2. In the Create new fatigue subcase field, enter fatsub_fpmtut. 3. Click Create.

4. For the Select existing fatigue subcase field, select the newly created fatigue subcase fatsub_fpmtut. fatsub_fpmtut is selected as the active fatigue subcase. Definitions in the following processes (analysis parameters, fatigue elements and properties, loading sequences, etc.) will be for this subcase. 5. Click Apply. This saves the current definitions and guides you to the next task Analysis Parameters of the Fatigue Analysis tree.

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Figure 252: Create and Select Active Fatigue Subcase to Process

Applying Fatigue Analysis Parameters 1. Make sure the task Analysis Parameters is selected in the Fatigue Analysis tree. 2. Select the following options: Analysis type

E-N

Stress combination method

Signed von Mises

Mean stress correction

SWT

FEA stress unit

MPA

Rainflow type

STRESS

Plasticity correction

NEUBER

3. Enter the following values: Gate 0.0

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Certainty of survival 0.5 4. Click Apply. This saves the current definitions and guides you to the next task Elements and Materials of the Fatigue Analysis tree. For details, consult the HyperWorks 2019 help.

Figure 253: Fatigue Analysis Parameters Definition

Defining the Fatigue Elements and Materials 1. Make sure the task Elements and Materials is selected in the Fatigue Analysis tree. 2. Click Add. A Material Data window opens. 3. For Element entity type, select Property - PSHELL. 4. For Element entity name, select shell. This is the skin coating the solid control arm. 5. Make sure Ultimate tensile strength (UTS) is selected to define the material data. 6. For UTS, enter the value 600.

7. For Input method of defining EN curve, select Estimate From UTS. 8. Click the Show EN curve definition icon

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An EN method description window introducing how to generate the EN material parameter opens. 9. Click Close. 10. For Material type, select Aluminum and Titanium Alloys and click Estimate. All the data for EN curve definition are automatically estimated. 11. Click Plot EN Curve at the bottom of the window to show the EN curve. 12. Close the EN Curve plot window. 13. For Layer of stress results in shell elements, select TOP. 14. For Surface finish, select No Finish. 15. For Surface treatment, select No Treatment. 16. Leave the field after Fatigue strength reduction factor blank. 17. Click Save to save the definition of the EN data for the selected elements. 18. Click Apply. This saves the current definitions and guides you to the next task Load-Time History of the Fatigue Analysis tree.

Figure 254: Material Data Definition

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Figure 255: Elements and Material Definition

Defining the Load-Time History 1. Make sure the task Load-Time History is selected in the Fatigue Analysis tree. 2. Click Add by File. A Load Time History window opens. 3. For Load-time history name, enter lth1. 4. For Load-time history type, select CSV. 5.

Click the Open load-time file icon An Open file browser window opens.

.

6. Browse for load1.csv. 7. Click Open > Import.

8. Click Save to write the new load-time history into HyperMesh database. 9. Create another load-time history named lth2 by importing the file load2.csv. 10. Click Plot L-T to show the load-time history. 11. Close the Load Time History window. 12. Click Apply. This saves the current definitions and guides you to the next task Loading Sequences of the Fatigue Analysis tree.

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Figure 256: Load-time History Definition

Figure 257: Import Load-Time History

Note: For a file of DAC format, it can very easily be imported in HyperGraphand converted to CSV format for use by FPM.

Loading Sequences In this step, one event consisting of two load time history is created; in other words, the linear superposition of the stress caused by the two load time history is requested during analysis. Using this event, one load sequence is constructed. 1. Make sure the task Loading Sequences is selected in the Fatigue Analysis tree.

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2. Click Add. A Loading Definition window opens. 3. For Select static loadcase, select SUBCASE1. 4. For Select load-time history, select lth1. 5. For Scale, enter the value 5.0.

6. Make sure Create new is selected using the radio buttons. 7. Enter Event1 for the newly created fatigue event name.

Figure 258: Associate Load-Time History with Static Subcase

8. Click Save > Add. A Loading Definition window opens. 9. For Select static loadcase, select SUBCASE2. 10. For Select load-time history, select lth2. 11. Enter the value 5.0 for Scale.

12. Make sure Existing is selected using the radio buttons. For Existing, select Event1. 13. Click Save > Apply. This saves the current definitions and guides you to the next task Submit analysis of the Fatigue Analysis tree.

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Figure 259: Loading Sequences Definition

Submitting the Job 1. Make sure the task Submit Analysis is selected in the Fatigue Analysis tree. 2.

Click the Save .fem file icon . A Save As browser window opens.

3. Set the directory in which to save the file, and for File name, enter ctrlarm_fpmtut.fem. 4. Click Save to close the window.

5. Click Save to save the OptiStruct model file. 6. For Run Option, select analysis. 7. Click Submit. This launches OptiStruct 2019 to run the fatigue analysis. If the job is successful, the new results files should be in the directory from which was selected. The default files written to the directory are:

ctrlarm_fpmtut.0.3.fat

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An ASCII format file which contains fatigue results of each fatigue subcase in iteration step.

OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

ctrlarm_fpmtut.h3d

Hyper 3D binary results file, with both static analysis results and fatigue analysis results.

ctrlarm_fpmtut.out

OptiStruct output file containing specific information on the file set up, the set up of your fatigue problem, compute time information, etc. Review this file for warnings and errors.

ctrlarm_fpmtut.stat

Summary of analysis process, providing CPU information for each step during analysis process.

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Figure 260: Submit Fatigue Analysis

Post-processing the Analysis 1. Make sure the task Post-processing is selected in the Fatigue Analysis tree. When fatigue analysis has completed successfully after the previous submit, it will automatically go into this task. 2. Click View and select the Results type Life.

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3. Check the top 0.1%, 1.0%, 5.0% average life, and Top 1, 2, 3 most damage elements lives. 4. Toggle the Result type to view the damage results summary. 5. Click Load H3D Results (HV). This launches HyperView to load the ctrlarm_fpmtut.h3d results file for more detailed results. 6. Click Close to unload Fatigue Process Manager.

Figure 261: Life Results Summary

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Figure 262: Damage contour in HyperView

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OS-T: 1360 NLSTAT Analysis of Gasket Materials in Contact This tutorial demonstrates how to carry out nonlinear implicit small displacement analysis in OptiStruct involving gasket materials and contact. Figure 263 below illustrates the structural model used for this tutorial: A 1mm thick cylindrical gasket is sandwiched between two co-axial steel cylindrical tubes. The outer cylinder is subjected to a pressure of 300 MPa on the outer surface as shown. Using symmetry boundary conditions, only a quarter of the geometry has been modeled. The gasket is connected to the inner and outer cylinders using contact.

Figure 263: Model and Loading Description

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK.

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This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the gasket_model.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The gasket_model.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating the Curves for Gasket Material First, define the loading-unloading curves for the gasket material. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter load-curve.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLES1 from the drop-down menu. 5. For TABLES1_NUM, enter 6 (number of rows in the table), and press Enter. 6. Click the Table icon

next to the Data field and enter the following values (X (closure) and Y

(pressure) fields) in the pop-out window. X

Y

0.0

0.0

0.005

200.0

0.05

450.0

0.135

700.0

0.22

820.0

0.287

830.0

7. Click Close. For details on pressure-closure definitions of gaskets, refer to the HyperWorks 2019 online help.

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Now, unloading curves can be created. 8. Create the unloading curve named unload-curve1 with the following X-Y data: X

Y

08

0

12

0

135

0

9. Next, create the second unloading curve named unload-curve2 with the following X-Y data: X

Y

17

0

2

0

22

0

10. Finally, create the third unloading curve named unload-curve3 with the following X-Y data: X

Y

0.23

0.0

0.265

360.0

0.287

830.0

Creating the Elasto-plastic Gasket Material The membrane behavior of the gasket needs to be defined. 1. In the Model Browser, right-click and select Create > Material. 2. For Name, enter gask_membrane.

3. Click Color and select a color from the color palette. 4. For Card Image, select MAT1 from the drop-down menu. 5. For E, enter 2.0E+04 and for NU, enter 0.2.

Next, you will define the nonlinear properties for the gasket material. 6. Create another material named gask_nonlin. 7. For Card Image, select MGASK.

8. Since this is an elasto-plastic gasket material, for gasket behavior leave BEHAV field as 0. 9. For initial yield pressure, leave the YPRS field blank for the solver to determine it automatically. 10. For tensile modulus EPL, enter 0.001.

11. For GPL to specify the shear modulus, enter 2000.

12. For MGASK_TABLU_NUM, enter 3 to specify the field for # of unloading curves.

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13. For TABLD, select load-curve. 14. Click

next to the Data field and select the following:

TABLU(1)

unload-curve1

TABLU(2)

unload-curve2

TABLU(3)

unload-curve3

Creating the Gasket Property 1. In the Model Browser, right-click and select Create > Property. 2. For Name, enter gasket_prop.

3. Click Color and select a color from the color palette. 4. For Card Image, select PGASK from the drop-down menu and click Yes to confirm. 5. For Material, click Unspecified > Material. 6. In the Select Material dialog, select gask_nonlin from the list of materials and click OK to complete the selection. 7. For MID1, select the gask_membrane material. 8. For STABMT field, select 1 to define some stabilization stiffness.

Figure 264:

9. Next, assign this property to the gasket component. Click on the component GASKET in the Model Browser. 10. For Property, select gasket_prop property.

Assigning 8-Noded Gasket Elements 1. Click on the 3D page from the main menu.

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2. Click the elem types panel and click 2D & 3D. 3. Click on elems, select by collector type and select the GASKET component. 4. Toggle hex8 =, and select the CGASK8 element type. 5. Click update > return.

Reviewing and Adjusting the Normals of the Gasket Elements 1. Click on 2D page from the main menu. 2. Click on the composites panel. 3. For comps, select the GASKET component and click display normals. The normals of the gasket elements are not in the thickness direction, but in the Z-direction, as shown below.

Figure 265:

So, adjusting the normals needs to be in thickness direction. 4. Display only the GASKET component. 5. Click on by nodes on bottom face and select the GASKET component. 6. For choosing the face nodes, click on nodes and select three nodes on a face of any gasket element in the thickness direction and click adjust normals. The normals are now adjusted to be in thickness direction of gasket, as shown below.

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Figure 266:

7. Click return to go back to the main menu.

Defining Contact between the Cylinders and Gasket Now the contact surface for the bottom surface of the top cylinder needs to be defined. 1. Hide the GASKET component and display only the SOLID1 component. 2. In the Model Browser, right-click and select Create > Contact Surface. 3. For Name, enter SOLID1_bottom.

4. Click Color and select a color from the color palette. 5. For Card Image, select SURF from the drop-down menu. 6. Click on Elements and on the yellow Elements panel. 7. Under the modeling window, select add solid faces from the selection menu. 8. Click elems >> displayed. 9. Click on face nodes, select the three nodes on the bottom surface (i.e. surface contacting the gasket, as shown below) and click add.

Figure 267:

10. Click return. 11. Next, hide the SOLID1 component and display only the SOLID2 component. 12. Create the contact surface SOLID2_top for the top surface of the SOLID2 component contacting the gasket.

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13. Similarly, repeat the steps and create GASKET_top and GASKET_bottom surfaces for the top and bottom surfaces of the GASKET component, respectively. Now, an interface between the top cylinder and gasket are created. 14. In the Model Browser, right-click and select Create > Contact. 15. For Name, enter SOLID1_GASKET.

16. Click Color and select a color from the color palette. 17. For Card Image, select CONTACT from the drop-down menu. 18. For MSID (master surface), select the SOLID1_bottom surface. 19. For SSID (slave surface), select the GASKET_top surface. 20. For TYPE, select STICK from the drop-down menu.

Figure 268:

Next, an interface between the bottom cylinder and gasket are created. 21. In the Model Browser, right-click and select Create > Contact. 22. For Name, enter SOLID2_GASKET.

23. Click Color and select a color from the color palette. 24. For Card Image, select CONTACT from the drop-down menu. 25. For MSID (master surface), select the SOLID2_top surface. 26. For SSID (slave surface), select the GASKET_bottom surface. 27. For TYPE, select STICK from the drop-down menu. Next, you create the interface between the bottom cylinder and gasket. 28. Click on create and for name, enter SOLID2_GASKET. 29. For type, enter CONTACT and click create.

30. Click on add to select the master and slave surfaces for this interface. 31. For master, select the SOLID2_top surface and click update. 32. For slave, select the GASKET_bottom surface and click update.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 33. Click review to review the interface.

Figure 269:

Defining Nonlinear Implicit Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter NLPARM.

3. Click Color and select a color from the color palette. 4. For Card Image, select NLPARM from the drop-down menu. 5. For NINC, enter 1.

Keep the remainder of the parameters set at the default values. For details on the nonlinear implicit parameters, consult the HyperWorks 2019 online help.

Creating NLSTAT Load Step 1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter NLSTAT.

3. Click Color and select a color from the color palette. 4. Click Analysis type and select nonlinear quasi-static from the drop-down menu. 5. For SPC, select SPC from the list of load collectors. 6. For LOAD, select LOAD from the list of load collectors. 7. For NLPARM, select NLPARM from the list of load collectors.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

Figure 270:

Defining Output Control Parameters 1. From the Analysis page, select control cards. 2. Click on GLOBAL_OUTPUT_REQUEST. 3. Below CONTF, DISPLACEMENT, STRAIN and STRESS, set the option to Yes. 4. Click return twice to go to the main menu.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 271: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter gasket_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the gasket_complete.fem was written. The gasket_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results In HyperView, plot the displacement and contact pressure contours at the end of the analysis.

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Figure 272: Contour of Displacements in Cylinders and Gasket Subject to Loading

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

Figure 273: Contour of Gasket Thickness Direction Pressure

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis

Figure 274: Contour of Contact Pressure

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OS-T: 1365 NLSTAT Analysis of Solid Blocks in Contact This tutorial demonstrates how to carry out nonlinear implicit small displacement analysis in OptiStruct, involving elasto-plastic materials, contact and continuing the nonlinear solution sequence from a preceding nonlinear loadcase. Figure 275 illustrates the structural model used for this tutorial, which is two square solid blocks made of elasto-plastic steel material. The dimensions of the blocks and the material parameters are outlined below. In the first nonlinear subcase, pressure loading is be applied to the top solid block, the top corners of which are constrained in X and Y directions. The top solid is in contact with the bottom solid, the bottom corners of which are constrained in X, Y and Z directions. The second nonlinear subcase is to simulate the unloading and is a continuation of the nonlinear solution sequence from the previous loading subcase.

Figure 275: Model and Loading Description

Units

Length: mm; Time: s; Mass: Mgg; (Force: N; Stress: MPa)

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis Top block

72 mm x 72 mm

Bottom block

100 mm x 100 mm

Thickness of blocks

20. mm

Material

Steel, Elasto-plastic

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3

Initial density ( ): 7.90e-9 kg/mm Young's modulus (E): 210000 MPa Poisson coefficient ( ): 0.3 Yield Stress ( 0): 850.0 MPa Imposed pressure

1000.0 MPa, applied at the center of top block

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the nlstat.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The nlstat.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Elasto-plastic Material First, the stress vs plastic strain curve for the material needs to be defined.

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1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter stress-strain.

3. Click Color and select a color from the color palette. 4. For Card Image, select TABLES1 from the drop-down menu. 5. For TABLES1_NU, enter 2 (number of rows in the table), and press Enter. 6. Click the Table icon

next to the Data field and enter the following values (x and y fields) in

the pop-up window.

Figure 276:

7. Click Close to close the dialog. Now, the elasto-plastic material needs to be updated. 8. In the Model Browser, click the material steel. The Entity Editor opens. 9. Click on the checkbox next to MATS1 to define the elastic-plastic material for NLSTAT analysis. 10. For TID, click Unspecified > Loadcol. 11. In the Select Loadcol dialog, select the stress_strain load collector and click OK. 12. Input the values, as shown below. TYPSTRN of 1 signifies specifying stress (Y) vs plastic strain (X).

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Figure 277:

Defining Contact between the Blocks The contact surfaces for the two blocks need to be defined. 1. In the Model Browser, right-click and select Create > Set. 2. For Name, enter top.

3. For Card Image, select SET_ELEM from the drop-down menu. 4. Leave the Set Type switch set to non-ordered type. 5. For Entity IDs, click Unspecified > Property. 6. In the Select Properties dialog, select the top solid block Solid1 and click OK.

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Figure 278:

7. Similarly create another set named bottom.

8. Repeat steps 3 through 6 for bottom block select the bottom solid Solid2. Next, the interface needs to be defined. 9. In the Model Browser, right-click and select Create > Contact. 10. For Name, enter SOLID_CONTACT.

11. Click Color and select a color from the color palette. 12. For Card Image, select CONTACT from the drop-down menu. 13. For MSID (master surface) and select Set from the extended selection menu. 14. Click the yellow Set panel and select the bottom block bottom in the pop-up window and click OK. 15. Similarly, for SSID (slave surface), select the top set. 16. For TYPE, select SLIDE from the drop-down menu. 17. For MORIENT, select NORM from the drop-down menu.

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Figure 279:

Defining Nonlinear Implicit Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter NLPARM.

3. Click Color and select a color from the color palette. 4. For Card Image, select NLPARM from the drop-down menu. 5. Enter the values as shown below:

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Figure 280:

Creating the 1st Nonlinear Load Step 1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter loading.

3. Click Analysis type and select Nonlinear quasi-static from the drop-down menu. 4. For SPC, click Unspecified > Loadcol. 5. From the Select Loadcol dialog, select SPC from the list of load collectors and click OK. 6. For LOAD, click Unspecified > Loadcol. 7. From the Select Loadcol dialog, select pressure from the list of load collectors and click OK. 8. For NLPARM, click Unspecified > Loadcol. 9. From the Select Loadcol dialog, select nlparm from the list of load collectors and click OK.

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Figure 281:

Creating the 2nd Nonlinear Load Step 1. For Name, enter unload.

2. The Analysis type should, again, be set to Nonlinear quasi-static from the drop-down menu. 3. For SPC, select SPC from the list of load collectors. 4. For NLPARM, select nlparm from the list of load collectors. Checkpoint: The unloading subcase (unload) does not contain the pressure load applied during the loading subcase (loading).

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Figure 282:

Defining Output Control Parameters 1. From the Analysis page, select control cards. 2. Click on GLOBAL_OUTPUT_REQUEST. 3. Below CONTF, DISPLACEMENT, STRAIN and STRESS, set the option to Yes. 4. Under STRAIN, set TYPE(1) to PLASTIC. 5. Click return twice to go to the main menu.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 283: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter nlstat_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the nlstat_complete.fem was written. The nlstat_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Using HyperView, plot the Displacement, the von Mises stress, plastic strains and contact pressure st contours at the end of the 1 (loading) step.

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Figure 284: Contour of Displacements in Blocks Subject to Loading

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Figure 285: Contour of von Mises Stress in Blocks Subject to Loading

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Figure 286: Contour of Plastic Strains in the Blocks Subject to Loading

Figure 287: Contour of Contact Pressure in the Block Interface After the 1st (Loading) Subcase nd

Next, change the subcase to the 2 that is unloading subcase and plot the displacement contour to see the change in displacements in the blocks subject to unloading.

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Figure 288: Contour of Displacements in Blocks Subject to Unloading in 2nd Subcase

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OS-T: 1370 Complex Eigenvalue Analysis of a Reduced Brake System In this tutorial, a modal complex eigenvalue analysis is performed on a simplified brake system to determine whether the friction effects can cause any squeal noise (unstable modes). The simplified brake system consists of a brake pad with frictional surface and back plate, and a contact plate. They were all modeled with solid elements. Spring elements (CELAS1) were created between the brake pad and the contact plate to measure the normal contact forces, as shown in Figure 289. The friction forces on the pad and the contact plate are proportional to the normal contact forces. The stiffness matrix terms representing the relationship between friction forces and normal displacements on the contact grids were saved in a DMIG Bulk Data file DMIG.pch. Assume the brake pad is in full contact with the plate at all time. The back plate of the brake pad and the contact plate were constrained to the ground.

Figure 289: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the brake.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating EIGRL and EIGC Cards In this step, a modal method is used to solve the complex eigenvalue problem, which is more computationally efficient compared to extracting the complex modes directly. With this approach, first, the real modes are calculated via a normal modes analysis. Then, a complex eigenvalue problem is formed on the projected subspace spanned by the real modes and thus much smaller than the real space. In this case, both EIGRL and EIGC cards need to be defined. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter eigrl.

3. Click Color and select a color from the color palette. 4. For Card Image, select EIGRL from the drop-down menu. 5. For ND, enter 20.

20 real modes are required to produce the reduced space for complex eigenvalue analysis.

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Figure 290:

6. Create another load collector named eigc. 7. For Card Image, select EIGC. 8. For NORM, select MAX. MAX option is used to normalize the eigenvectors. 9. For ND0, enter 12.

The desired number of roots to be extracted is 12.

Retrieving Friction Data and Defining Analysis Parameters 1. Go to the Analysis page, then click control cards. 2. Click INCLUDE_BULK. 3. Input the name of the include file, DMIG.pch. 4. Click return to go back to control cards. 5. Click K2PP. 6. In K2PP panel, set number_of_k2pps= 1. 7. In the field of K2PP=, enter KF.

KF is the name of the DMIG Data Entry.

8. Click return and back to control cards. Retrieve the friction coefficients from the DMIG.pch file.

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9. Click PARAM. 10. Check the small box in front of parameter G. 11. Click [G_V1] and input 0.2 as the structural damping coefficient. 12. Check the small box in front of parameter FRIC. 13. Click [VALUE] and input 0.05.

Friction factor 0.05 is used to scale the friction coefficient from DMIG Data Entry.

14. Click return twice and go back to the Analysis page.

Defining a Load Step for Modal Complex Eigenvalue Analysis 1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter complex_eigen.

3. Click Analysis type and select Complex eigen (modal) from the drop-down menu. 4. For SPC, click Unspecified > Loadcol. 5. In the Select Loadcol dialog, select SPC from the list of load collectors and click OK. 6. For CMETHOD, click Unspecified > Loadcol. 7. In the Select Loadcol dialog, select eigc from the list of load collectors and click OK. 8. For METHOD(STRUCT), click Unspecified > Loadcol. 9. In the Select Loadcol dialog, select eigrl from the list of load collectors and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 291: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter brake_complex for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the brake_complex.fem was written. The brake_complex.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Complex eigenvalue analysis computes the complex modes of the structure. The eigenvalues of the complex modes can be found in brake_complex.out file. The complex eigenvectors can be reviewed in HyperView. 1. Load the brake_complex.out file in a text editor.

The complex modes contain the imaginary part, which represents the cyclic frequency, and the real part which represents the damping of the mode. If the real part is negative, then the mode is said to be stable. If the real part is positive, then the mode is unstable. The eigenvalues of the complex modes are shown below:

Figure 292: th

As you can see, the 5 mode was divergent while all of the other modes were stable. The friction coefficient parameter can be reduced by setting the PARAM,FRIC factor from a value of 0.05 to 0.01, and all roots become stable. It illustrates that there is a stability threshold between the friction factor 0.05 and 0.01. It can be determined by resetting the scale factor of PARAM, FRIC and rerunning the model till the damping value of this mode approaches zero. 2. Load the brake_complex.h3d file into HyperView to review complex eigenvectors.

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OS-T: 1371 Brake Squeal Analysis of Brake Assembly In this tutorial you will perform a brake squeal analysis on a brake assembly. Disc brakes are operated by applying a clamping load using a set of brake pads on the disc. The friction generated between the pads and the disc causes deceleration, and can potentially induce a dynamic instability of the system. This phenomena is known as brake squeal. For this model OptiStruct will predict an unstable mode and the instability is seen to occur at the point of mode coalescence, i.e., a pair of modes occur at the same frequency (mode coupling), and one of them is unstable. The unstable mode can be identified during complex eigenvalue extraction because the real part of the eigenvalue corresponding to an unstable mode is positive. You can further design brake system which can be stabilized by changing the shape of the brake pads or material properties of the brake components to decouple the modes (which is not shown in this tutorial). The purpose of this tutorial is to conduct brake squeal analysis and identify the unstable modes (if they exist).

Figure 293: Model Review

brsq.fem File Data • Hexahedral Mesh is created for the brake assembly • All parts are defined with material MAT1

• All parts are defined with Solid Element Property • A cylindrical coordinate system is defined with respect to the disc • S2S Contacts are defined between brake pad and disc Two sub-cases are defined:

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Figure 294:

1. Sub-case CLAMPLOAD: Nonlinear static analysis Pressure Load on Insulator (Inner and Outer), with SPC (DOF1).

Figure 295:

2. Sub-case ROTOR: Nonlinear static analysis with CNTNLSUB. Pressure Load on Pad and Rotation of the Disc, with non-zero SPC (DOF2).

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Figure 296:

Tip: a. The prescribed rotation should be large enough to ensure the contact between the disc and the pad is in kinetic friction, but small enough to ensure small displacement NLSTAT. b. Kinetic friction is a constant value (independent rotation using SPCD is equivalent to prescribing outcome is that the contact nodes are in kinetic matter how fast or how far you move this using

of velocity), hence prescribing rotational speed. The important friction mode and it does not SPCD.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the brsq.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

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6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating EIGRL and EIGC Cards In this step, a modal method is used to solve the complex eigenvalue problem, which is more computationally efficient compared to extracting the complex modes directly. With this approach, first, the real modes are calculated via a normal modes analysis. Then, a complex eigenvalue problem is formed on the projected subspace spanned by the real modes which is much smaller than the real space. Here, both EIGRL and EIGC cards need to be defined. 1. In the Model Browser, right-click and select Create > Load Collector. 2. In the Name field, enter modal_space.

3. Click Color and select a color from the color palette. 4. Click Card Image and select EIGRL from the drop-down menu. 5. Click V2 and input 5000.

5000 is defined as the highest frequency bond.

6. Click ND and input 100.

100 real modes are required to produce the reduced space for complex eigenvalue analysis.

7. Create another load collector named ceig_squeal. 8. Click Card Image, and select EIGC. 9. Click NORM and select MAX. MAX option will be used to normalize the eigenvectors. 10. Click ND0 and input 55.

The desired number of roots to be extracted is 55.

Defining Load Step for Modal Complex Eigenvalue Analysis 1. In the Model Browser, right-click and select Create > Load Step. 2. In the Name field, enter BRSQ.

3. Click Analysis type and select Complex eigen (modal) from the drop-down menu. 4. For SPC, select DOF2 from the list of load collectors. 5. For CMETHOD, select ceig_squeal_ from the list of load collectors. 6. For METHOD(STRUCT), select modal_space from the list of load collectors. 7. For STATSUB (BRAKE), select Sub-case ROTOR (ID 2). Tip: Create STATSUB (BRAKE) manually if this is not yet supported in HyperMesh.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 297: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter brsq for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the brsq.fem was written. The brsq.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Complex eigenvalue analysis computes the complex modes of the structure. The eigenvalues of the complex modes can be found in the brsq.out file. The complex eigenvectors can be reviewed in HyperView. 1. Load the brsq.out file in a text editor.

The complex modes contain the imaginary part, which represents the cyclic frequency, and the real part which represents the damping of the mode. If the real part is negative, then the mode is said to be stable. If the real part is positive, then the mode is unstable. The eigenvalues of the complex modes are shown below:

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Figure 298:

2. Load the brsq.h3d file into HyperView to review complex eigenvectors.

Figure 299:

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OS-T: 1372 Rotor Dynamics of a Hollow Cylindrical Rotor In this tutorial you will perform Rotor Dynamics analysis on a hollow cylindrical rotor. For rotating components, additional forces like the gyroscopic force and circular damping force exist and are critical in the study of their response. It is important to determine these effects of rotating components on the system as a whole. Here the complex eigenvalue analysis for 0, 10K, 30K, and 50K RPM are run. The objective is to determine critical frequencies, and generate Campbell diagram when subjected to a static imbalance from the rotor. At the critical frequency you observe forward/backward cylindrical and conical whirl (mode shapes).

Figure 300: Model Review

rotor.fem File Data • 1D Line Mesh is created using beam elements for the Rotor • Rotor is defined with Material MAT1

• Rotor is defined with Beam Property • SPC condition is defined in the model

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Figure 301:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

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4. Select the rotor.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating EIGRL and EIGC Cards In this step, a modal method is used to solve the complex eigenvalue problem, which is more computationally efficient compared to extracting the complex modes directly. With this approach, first, the real modes are calculated via a normal modes analysis. Then, a complex eigenvalue problem is formed on the projected subspace spanned by the real modes which is much smaller than the real space. Here, both EIGRL and EIGC cards need to be defined. 1. In the Model Browser, right-click and select Create > Load Collector. 2. In the Name field, enter EIGRL.

3. Click Color and select a color from the color palette. 4. Click Card Image and select EIGRL from the drop-down menu. 5. Click V2 and input 250.0.

250.0 is defined as the highest frequency bond.

6. Create another load collector named EIGC. 7. Click Card Image, and select EIGC. 8. Click NORM and select MAX.

MAX option will be used to normalize the eigenvectors. 9. Click ND0 and input 55.

The desired number of roots to be extracted is 55.

Defining Grids for the Rotor Line Model 1. Right-click in the Model Browser and select Create > SET. 2. Click Name and enter ROTORG_SET.

3. Click Card Image and select ROTORG from the drop-down menu. 4. Click Entity IDs and click on nodes. 5. Select nodes by collector and select CBEAM, and proceed. 6. Check the box next to the RSPINR field since every rotor defined via ROTORG requires a corresponding RSPINR entry. 7. Click the field next to GRIDA and then Node. 8. In the selection panel, click Node and enter 10000 in the ID= field.

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OptiStruct Tutorials Advanced Small Displacement Finite Element Analysis 9. Similarly, for GRIDB, enter 10001.

10. Click on the field next to SPTID and enter 1.0.

Creating RSPEED Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. Click Name and enter RSPEED.

3. Click Card Image and select RSPEED from the drop-down menu. 4. Click S1 and enter 0.0, which is first reference rotor speed.

5. Click DS and enter 10000.0, which is increment in reference rotor speed.

6. Click NDS and enter 5, which is the number of reference rotor speed increments.

Creating RGYRO Load Collector 1. In the Model Browser, right-click and select Create > Load Collector. 2. Click Name and enter RGYRO.

3. Click Card Image and select RGYRO from the drop-down menu. 4. Click SYNCFLG and select ASYNC from the drop-down menu. Tip: This is set to run an Asynchronous Rotor dynamics analysis. 5. Click REFROTR and click set. 6. Select ROTORG_SET and click OK. 7. Check the field next to SPEED_ID. 8. Next to the SPEED field, click Unspecified > Loadcol and select RSPEED from the pop-up window.

Defining Load Step for Modal Complex Eigenvalue Analysis 1. In the Model Browser, right-click and select Create > Load Step. 2. In the Name field, enter Rotor Dynamics.

3. Click Analysis type and select Complex eigen (modal) from the drop-down menu. 4. For SPC, select SPC from the list of load collectors. 5. For CMETHOD, select EIGC from the list of load collectors. 6. For METHOD(STRUCT), select EIGRL from the list of load collectors. 7. Under SUBCASE OPTIONS, check the field next to RGYRO and then RGYRO_ID. 8. Click on the field next to ID to select load collector RGYRO.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 302: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rotor_async for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the rotor_async.fem was written. The rotor_async.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Running the Model 1. Click on the RGYRO card in the Model Browser. 2. Click SYNCFLG and change from ASYNC to SYNC from the drop-down menu. 3. From the Analysis page, enter the OptiStruct panel. 4. Click Save as following the input file: field. A Save As browser window opens. 5. Select the directory where you would like to write the file and enter the name rotor_sync.fem in the File name: field. 6. Click Save. Note the name and location of the file displays in the input file: field. 7. Set the export options: toggle to all.

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8. Set the run options: toggle to Analysis. 9. Set the memory options: toggle to memory default. 10. Click OptiStruct. This launches the OptiStruct job. If the job completed successfully, new results files can be seen in the directory where the OptiStruct model file was written. The rotor_sync.out file is a good place to look for error messages that will help to debug the input deck if any errors are present.

Viewing the Results Complex eigenvalue analysis computes the complex modes of the structure. The eigenvalues of the complex modes can be found in rotor_async.out file. The complex eigenvectors can be reviewed in HyperView. 1. Read the rotor_async.out in HyperView and follow the instructions in the below link to get the Campbell Diagram and review the critical frequencies at the intersection points. http://www.altairhyperworks.com/hwhelp/Altair/hw14.0/help/hg/hg.htm?campbell_diagram.htm

Figure 303:

TableView in HyperView provides a summary for the critical frequencies.

Figure 304:

2. Load the rotor_sync.out file in a text editor.

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The Frequencies which you get from the Synchronous Rotor dynamic analysis give you the critical frequencies. The complex modes contain the imaginary part, which represents the cyclic frequency, and the real part which represents the damping of the mode. If the real part is negative, then the mode is said to be stable. If the real part is positive, then the mode is unstable.

Figure 305: Eigenvalues of the Complex Modes

3. Compare to verify the Critical Frequencies which you obtained from the intersection points of Step 10.1 and the frequencies you obtained in the rotor_sync.out file. 4. Load the rotor_async.h3d file into HyperView to review and verify below Cylindrical and Conical mode shapes.

RPM

Cylindrical Modes Backward

Cylindrical Modes Forward Mode #: 3

Mode #: 4

Conical Modes Forward

Conical Modes Backward

Mode #: 5

Mode #: 6

10,000

1.253E+001

1.253E+001

2.071E+001

2.263E+001

30,000

1.253E+001

1.253E+001

1.896E+001

2.472E+001

50,000

1.253E+001

1.253E+001

1.738E+001

2.697E+001

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OS-T: 1375 Response Spectrum Analysis of a Structure This tutorial demonstrates how to perform a Response Spectrum Analysis on a structure. This kind of analysis provides an estimate of peak structural response to a structure subject to dynamic excitation. The analysis uses response spectra for prescribed dynamic loading and results of normal modes analysis to calculate this estimate. In the model used shown below in Figure 306, a building structure is modeled using CBEAM elements having solid circular x-section (that is type 'ROD'). The base of the building structure will be constrained for all degrees of freedom and the structure will be excited in the global Z direction.

Figure 306: Building Structure HyperMesh Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the building_ResponseSpectrumAnalysis.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The building_ResponseSpectrumAnalysis.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating EIGRL Load Collector Define the EIGRL card to calculate the normal modes of the model. 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter eigrl_card. 3. Click Color and select a color from the color palette. 4. For Card Image, select EIGRL from the drop-down menu. 5. Click ND and enter a value of 10.

Creating Constraints 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter constraints.

3. Click Color and select a color from the color palette. 4. For Card Image, select None from the drop-down menu. 5. Go to the Analysis page. 6. Click constraints. 7. In the create subpanel, confirm the entity is set to nodes , click on nodes and select the 4 nodes at the bottom of the model, as shown in the figure below.

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Figure 307: Selecting Nodes for Defining Constraints

8. Check all dofs (that is, dof1 to dof6) with the value 0.000, confirm load types is set to SPC, and click create. The constraints are created as shown in the figure below.

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Figure 308: Constraints Defined for the Model

9. Click return to exit the Constraints panel.

Defining the Input Response Spectrum 1. Go to the Utility tab. If the Utility menu is not displayed, select View > Browsers > HyperMesh > Utility. 2. At the bottom of the Utility menu, click the FEA panel. 3. Under Tools, click TABLE Create. 4. Select Import Table under Options and TABLED1 under Tables. 5. Click Next. 6. Under Options, select Create New Table. 7. For Name, enter tabled1_card. 8. Click Browse.

9. For Files of type: change to CSV (*.csv), select the file sourceFileTABELD1.csv (which contains the 'x' and 'y' values to define the input response spectrum, with frequency plotted on the x-axis and acceleration on the y-axis) located in your working directory from the optistruct.zip file. 10. Click Open. If the Import TABLED1 GUI is minimized, click on it on the taskbar.

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11. In the Import TABLED1 GUI, click Apply. A message is displayed indicating the creation of the TABLED1 card. 12. Click OK for this message.

13. Click Exit on the Import TABLED1 GUI (if you do not see the GUI, check the taskbar and click on the Import TABLED1 GUI). 14. To see the plot corresponding to the TABLED1 card created above, open the TABLE Create on the Utility menu on the FEA panel. a) Select the option Create/Edit Table. b) For Tables select TABLED1. c) Under Options, select Edit Existing Table. d) Next to Select select tabled1_card and click Plot.

e) After reviewing the plot, click on Close in the Plot window and Exit on the Create/Edit TABLED1 GUI.

Figure 309: Plot of the TABLED1 Card

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Defining the DTI, SPECSEL Card This card specifies the type of spectrum and damping values associated with the input response spectrum defined using TABLED1 card in the previous step. 1. Click the Model tab to bring up the Model Browser. 2. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 3. For Name, enter dti_card.

4. For Card Image, select DTI. 5. For TYPE, select A, since the input response spectrum is a plot of acceleration v/s frequency. 6. Click the Table icon

next to the Data field. In the pop-out window, select tabled1_card for

TID(1) and enter 0.02 for DAMP(1).

The damping value is in the units of fraction of critical damping.

Defining the RSPEC Load Collector This card provides the specifications of the Response Spectrum Analysis. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter rspec_card.

3. For Card Image, selectRSPEC. 4. For directional combination method, DCOMB, select ALG. 5. For modal combination method, MCOMB, select SRSS. 6. Click CLOSE and enter a value of 1.000 in the input box. 7. For RSPEC_NUM_DTISPEC, enter 1. 8. Click

next to Data. In the pop-out window, select dti_card for the DTISPEC field, and for

SCALE, enter the value 9800.0.

9. Since the direction of excitation for the structure is the Global Z direction, enter 0.0 for X(0), 0.0 for X(1), and 1.0 for X(2), respectively. 10. Click Close to exit the window.

Defining the Modal Damping for the Structure 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter tabdmp1_card.

3. For Card Image, select TABDMP1. 4. For TYPE, select CRIT. 5. For TABDMP1_NUM, enter 2.

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next to the Data field and enter the values 0.0, 0.02, 50.0 and 0.02 for f(1), g(1), f(2)

and g(2), respectively in the window. 7. Click Close to exit the window.

Defining the PARAM Cards 1. On the Analysis page, click control cards panel, click next twice, and then click PARAM panel. 2. Scroll down the list of available params, check the box next to COUPMASS, and for the value, select YES, so the coupled mass matrix approach is used for eigenvalue analysis. 3. Scroll down the list of available params, check the box next to EFFMASS, and for the value, select YES, so the modal participation factors and effective mass are computed and output to the .out file. 4. Click return to exit the panel.

Defining the Output Request Displacements are output by default. 1. To output stress from the Analysis page, enter the control cards panel. 2. Click next to the page which has the GLOBAL_OUTPUT_REQUEST panel. 3. Click GLOBAL_OUTPUT_REQUEST, scroll down the list to STRESS and check it. 4. For OPTION(1), select ALL. 5. Click return twice to exit the control cards panel.

Defining the Response Spectrum Analysis Load Step 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter response_spec.

3. Click Analysis type and select Response spectrum from the drop-down menu. 4. For SPC, click Unspecified > Loadcol. 5. In the Select Loadcol dialog, select constraints from the list of load collectors and click OK. 6. For RSPEC, click Unspecified > Loadcol. 7. In the Select Loadcol dialog, select rspec_card from the list of load collectors and click OK. 8. For METHOD(STRUCT), click Unspecified > Loadcol. 9. In the Select Loadcol dialog, select eigrl_card from the list of load collectors and click OK. 10. For SDAMPING(STRUCT), click Unspecified > Loadcol. 11. In the Select Loadcol dialog, select tabdmp1_card from the list of load collectors and click OK. 12. Click return to exit the Loadsteps panel. 13. From the Analysis page, enter the OptiStruct panel.

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14. Click Save as following the input file: field. A Save file browser window opens. 15. Select the directory where you would like to write the file and enter the name for the file in the File name: field. Note: Save the file in a folder different from the folders under HyperWorks installation folder. 16. Click Save. Note: The name and location of the file displays in the input file: field. 17. Set the export options: toggle to all. 18. Set the run options: toggle to Analysis. 19. Set the memory options: toggle to memory default. 20. Click OptiStruct. This launches the OptiStruct job. 21. If the job completed successfully, new results files can be seen in the directory where the OptiStruct model file was written. The .out file is a good place to look for error messages that will help to debug the input deck if any errors are present and this can be done by clicking on the view .out button in the OptiStruct panel.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 310: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter building_ResponseSpectrumAnalysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all.

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6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the building_ResponseSpectrumAnalysis.fem was written. The building_ResponseSpectrumAnalysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. In the HyperView Results Browser, expand the Results folder, then expand the Vector folder and contour displacement results by selecting Mag under Displacement.

Figure 311: Displacement Contour

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3. To contour stresses, expand the Scalar folder under Results, expand Element Stresses (1D) and contour the stress you want to see. Shown below is the contour of CBAR/CBEAM Long.Stress SAMAX.

Figure 312: Stress Contour

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OS-T: 1380 Computation of Equivalent Radiated Power Computation of the equivalent radiated power (ERP) is a simplified method to gain information about maximum dynamic radiation of panels for excitations in frequency response analysis. This tutorial demonstrates how to set up the computation request of ERP on an existing frequency response analysis. The model is a front cover of catalytic converter in a car exhaust system, as shown in Figure 313. The frequency analysis setup is already made for this model where the cover is constrained at two ends, and the excitation loading is applied at the center of the cover. The loading frequency is defined by FREQ1 card; from 120.0 to 400.0 Hz with an interval of 1.0. You need to define ERP panels (ERPPNL) and ERP output request.

Figure 313: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the cover.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The cover.fem database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating ERPPNL Set ERPPNL is defined as a set of elements. An element set ERP_elem has been predefined in the model. It can be reviewed in HyperMesh. 1. Go to the entity sets panel on Analysis page. 2. Click review and select ERP_elem. The elements should be highlighted on the screen. 3. Click return to go back to the main menu. 4. In the Model Browser, right-click and select Create > Set. A default set template is now displayed in the Entity Editor below the Model Browser. 5. For Name, enter ERPPNL.

6. For Card Image, select ERPPNL and click Yes to confirm. 7. For Entity IDs, click Unspecified > Sets. 8. In the Select Sets dialog. select the ERP_elem set and click OK.

Defining ERP Output Request You will request the ERP output in control cards panel. 1. From the Analysis page, click control cards. 2. Go to the GLOBAL_OUTPUT_REQUEST panel. 3. Check the box in front of ERP and enter 2 in the ERP_NUM field.

4. Set FORMATs, GRIDs, and OPTIONs for the ERP output, as shown below.

Figure 314: ERP output

The grid contribution of each grid in addition to the ERP results for the panel is output to an .h3d file. ERP panel results are output to punch format.

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5. Click return twice to return to the Analysis page.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 315: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cover_ERP for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the cover_ERP.fem was written. The cover_ERP.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Post-processing the ERP Results in HyperView 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Select Subcase 1 (frf) as the current load case in the Results browser. 3. Select the last load step where frequency is 50.0Hz. 4. On the Results toolbar, click

to open the Contour panel.

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5. Select Equivalent Radiated Power (ERP_elem) as Result type and then select Panel. 6. Click Apply. ERP results on panel should be plotted. 7. Select Equivalent Radiated Power (ERP_elem) as Result type and then select Grid Contributions. 8. Click Apply. The contour of grid contributions to ERP should be loaded.

Figure 316: ERP Results in HyperView

Post-processing the ERP Results in HyperGraph 1. Launch HyperGraph. 2. Click Build Plots. 3. Load cover_ERP.pch file in Data file.

4. Check that X Type is set to Frequency [Hz]. 5. Check that Y Type is set to Subcase 1 ERP. 6. Select Frf ERP_elem in Y Request and ERP in Y Component field. 7. Click Apply. The plot of ERP panel results vs loading frequency should be loaded, as shown below. The ERP (dB) results are available, as well.

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Figure 317: ERP Results in HyperGraph

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OS-T: 1385 Heat Transfer Analysis on Piston Rings with GAP Elements Piston rings fit on the outer surface of a piston in an engine. They support heat transfer from the piston to the cylinder wall. This tutorial demonstrates running a heat transfer analysis on a set of piston rings. 2

The inner ring takes the heat flux (10.0W/m ) from the piston. The outer surface of the ring that contacts the cylinder wall has zero degree temperatures. FREEZE gap elements are used to model the contact between the two rings. Thermal conduction property PGAPHT is defined for gap elements to simulate the heat transfer between the rings. The thermal boundary condition, heat flux loading, and a linear steady state heat conduction subcase have already been defined in the model. You will focus on how to define PGAPHT for gap elements in this exercise.

Figure 318: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the Rings.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating PGAP and PGAPHT Property Create PGAP and PGAPHT property before creating gap elements. 1. In the Model Browser, right-click and select Create > Property. A default PSHELL property template displays in the Entity Editor below the Model Browser. 2. In the Entity Editor, set the Name to PGAP.

3. For Card Image, select PGAP from the drop-down menu and click Yes to confirm. 4. Set U0= to 0.0.

5. Check the box next to MU1_opts. 6. Click on the field next to Options and select FREEZE from the drop-down menu. 7. Check the box next to PGAPHT. 8. Check the box next to KAHT_opts. KAHT=AUTO determines the value of KAHT for each gap element using the conduction of surrounding elements. The PGAP and PGAPHT definition should be the same. The heat transfer conduction property of gap elements has been created.

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Figure 319:

Creating CGAPG Elements Here defining CGAPG elements with predefined node and element sets, GAPgrids and GAPelems is done. GAPgrids contains the nodes on the outer surface of the inner ring. GAPelems contains the solid elements on the inner surface of the outer ring. The sets can be reviewed in entity sets on the Analysis page. 1. In the Model Browser, right-click and select Create > Component.

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A default component template is now displayed in the Entity Editor below the Model Browser. 2. For Name, enter PGAP.

3. For Property, click Unspecified > Property. 4. In the Select Property dialog, select PGAP and click OK. PGAP should be set to current component automatically.

Figure 320:

5. Select the 1D page. Click gaps and go to the create subpanel. 6. Check the option nodes-elems. 7. Click the highlighted nodes button and click by sets. 8. Check the box in front of GAPgrids and click select. 9. Click the highlighted elems button and click by sets. 10. Check the box in front of GAPelems and click select. 11. Face nodes need to be picked for the solid elements in GAPelems. 12. Go to the Model Browser and hide Ring2 under Component. The component Ring1 should be displayed on the screen and the inner layer solid elements should be highlighted. 13. Click face nodes and select the nodes on the inner surface of the highlighted solid elements, as shown below.

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Figure 321: Face Nodes

14. Click property= and select PGAP. If the CGAPG elements are created in predefined GAP component, there is no need to specify the property here since GAP is already linked to PGAP property. 15. Click create. The CGAPG elements with heat transfer conduction property are created.

Figure 322: Overview of CGAPG Elements

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As described at the beginning of the tutorial, the heat transfer boundary condition SPC_heat and heat flux input flux are predefined in the model. An OptiStruct steady state heat conduction loadstep, referring to SPC_heat and flux, has been defined as well. The heat transfer results are requested in Loadsteps panel. Refer to tutorial OS-T: 1080 Coupled Linear Heat Transfer/Structure Analysis for the details on how to define heat transfer boundary condition, heat flux, and the output request. Without PGAPHT, the heat cannot be transferred through the gap elements. In this case, the outer ring remains zero degree and the inner ring takes all heat, as shown in the temperature results in Figure 323. Run the completed model and compare the results with PGAPHT to the results below.

Figure 323: Temperature Results without PGAPHT

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 324: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Rings_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the Rings_complete.fem was written. The Rings_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Post-processing the Results Temperature and flux contour results for the steady state heat conduction analysis are computed by OptiStruct. HyperView will be used to post-process the results. 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. On the Results toolbar, click

to open the Contour panel.

4. Select Subcase 1 - heat transfer as the current load case in the Load Case and Simulation Selection window. 5. Select the first pull-down menu below Result type and select Grid Temperatures(s). 6. Click Apply. A temperature contour plot is now available.

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Figure 325: Results of Heat Transfer Analysis

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OS-T: 1390 Pretensioned Bolt Analysis of an IC Engine Cylinder Head, Gasket and Engine Block System This tutorial outlines the procedure to perform both 1D and 3D pretensioned bolt analysis on a section of an IC Engine. The pretensioned analysis is conducted to measure the response of a system consisting of the cylinder head, gasket and engine block connected by four head bolts subjected to a pretension force of 4500 N each.

Figure 326: Model Showing the Cylinder Head, Engine Block and Head Bolts

The model consists of eight predefined components along with their corresponding property and material allocations. A contact surface (PT_Surf) has been defined, which is used for 3D pretensioning of an existing pretension surface. The pretension sections for 1D pretensioning have also been created on two of the four bolts and the sectioned bolts are reconnected using 1D beam elements (via rigids). A predefined visualization aid is also available under View, which allows the user to easily look at the pretensioned sections of the four bolts. Contact surfaces and Contact Interfaces (TYPE=FREEZE) between the various parts have also been created so you can focus on the Pretensioning aspect of the tutorial.

Pretensioned Bolt Analysis Many engineering assemblies are put together using bolts, which are usually pretensioned before application of working loads. A typical sequence is described below. For further detailed information, refer to Pretensioned Bolt Analysis in the User Guide.

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In Step 1, upon preliminary assembly of the structure, the nuts on respective bolts are tightened, usually by applying prescribed torque (which translates into prescribed tension force according to the pitch of the thread). As a result, the working part of the bolt becomes shorter by a distance . This distance depends upon the applied force, the compliance of the bolt and of the assembly being pretensioned.

Figure 327: Step 1 of Pretensioned Assembly - Application of Pretensioning Loads

From the perspective of FEA analysis, it is important to recognize that: • Pretensioning actually shortens the working part of the bolt by removing a certain length of the bolt from the active structure (in reality this segment slides through the nut, yet the net effect is the shortening of the working length of the bolt). At the same time the bolt stretches, since now the smaller effective length of the bolt material has to span the distance from the bolt mount to the nut. • Calculation of each bolt's shortening , due to applied forces F, requires FEA solution of the entire model with the pretensioning forces applied. This is because the amount of nut movement, due to given force depends on the compliance of the bolts, of the assembly being bolted and is also affected by cross-interaction between multiple bolts being pretensioned. At the end of Step 1, the amount of shortening for each bolt is established and "locked", simply by leaving the nuts at the position that they reached during the pretensioning step. In Step 2, with the shortening of all the bolts "locked", other loads are applied to the assembly (Figure 328). At this stage the stresses and strains in the bolts will usually change, while the length of material removed remains constant for each bolt.

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Figure 328: Step 2 of Pretensioned Assembly - Application of Working Loads with 'Locked' Bolt Shortening

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the Pretension.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Pretension.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Setting Up the Model This tutorial helps the you apply 1D and 3D bolt pretensioning to the four head bolts (two of each) and then apply a pressure load to the constrained system. The applied pressure load models the pressure on the inside walls of an IC engine due to combustion. Pressure within the engine compartment varies with time (transient); however, you capture the response of the system at a specific instant frozen in time. A constant single-valued pressure load of 1 Pascal is applied to the inner walls of the cylinder head and the engine block. Gasket behavior is nonlinear and it may undergo cycles of loading and unloading which lead to changes in its properties at each step. In this tutorial, which focuses on 1D and 3D pretensioning, the loading and unloading paths for the gasket material are pre-populated in the MGASK Data Entry via the TABLES# entries referenced by corresponding load collectors. As a quasi-static analysis is running, the initial applied pressure load is compared with corresponding values within the loading/unloading path tables and the initial material properties of the gasket are determined. The nonlinear properties of the gasket via the MGASK Data Entry are a function of pressure and the closure distance (Refer to MGASK Bulk Data Entry for more information). FREEZE contact has been predefined for all parts in contact.

Figure 329: Tutorial Process Flow

Reviewing Material Properties The imported model contains a large amount of pre-populated information which allows us to focus on the pretensioning section in this tutorial. As previously explained, all material and properties are predefined for the gasket, engine block, cylinder head and head bolts. The material properties of steel are assigned to all components except the gasket. 1. In the Model Browser, right-click and select Expand All. 2. Click on STEEL in the Model Browser under Material. The MAT1 entry is displayed in the Entity Editor with pre-populated field values.

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3. Make sure that the values on the MAT1 Bulk Data Entry for the material properties of steel are input as shown below.

Figure 330: Reviewing the Material - Steel

4. Select MAT1_gask in the Model Browser. 5. Make sure that the values on the MAT1 Bulk Data Entry for the material properties of the gasket are input as shown below.

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Figure 331: Reviewing the Material - Gasket

6. Click on MGASK. 7. Make sure that the values on the MGASK Bulk Data Entry for the material properties of the gasket are input as shown below.

Figure 332: Reviewing the Nonlinear Gasket Material Properties - MGASK

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Tip: The TABLD and TABLU(1) fields (Gasket loading and unloading paths) in Figure 332 are defined by TABLES1 Bulk Data Entries in separate load collectors named Gask_Load and Gask_Unload1, respectively. 8. Click on Gask_Load in the Load Collector folder and then click the table icon

next to the

Data field. 9. Make sure that the values on the TABLES1 Bulk Data Entry defining the gasket loading paths are input as shown below.

Figure 333: Reviewing the Gasket Loading Paths - TABLES1

10. Similarly, make sure that the values on the TABLES1 Bulk Data Entry defining the gasket unloading paths (load collector Gask_Unload1) are input as shown below.

Figure 334: Reviewing the Gasket Unloading Paths - TABLES1

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Tip: You can review, in a similar manner, the remaining predefined data entries like properties and load collectors. The procedure for load collector review is not as straight forward, as shown above in some cases; however, this has been thoroughly illustrated in various other tutorials for the user's benefit. 11. The gasket normal direction is now reviewed by clicking on normals in the Tools panel. 12. To select the gasket component, use the Show/Hide tool (Figure 335 ) to hide the cylinder head thereby exposing the gasket to view.

Figure 335: Masking (Show/Hide) Tool

13. Click on the Show/Hide icon, and right-click on the cylinder head to hide it from view. The gasket should now be visible.

Figure 336: Exposing the Gasket Component to View Using the Masking Tool

14. In a similar fashion, hide (right-click) the engine block from view to be able to better visualize the gasket normals. 15. Click the Show/Hide icon again to deselect it and select the gasket directly from the modeling window and click display normals. The gasket normals can be seen in the modeling window, as shown in Figure 337. Notice that all the normals point in the negative Z direction.

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Figure 337: Selecting the Gasket Component

Figure 338: Displaying the Gasket Normals (Negative Z Direction)

This concludes the review section of the tutorial. You will now focus on generating contact interfaces, contact surfaces and applying pretensioning to the head bolts.

Applying 1D and 3D Bolt Pretensioning Bolt pretensioning analysis determines the response of a system which contains bolts holding two or more components together as a result of pretensioning. In OptiStruct, pretensioning is applied

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in an earlier subcase and it is subsequently referenced to in the subcase where its effect is sought (STATSUB(PRETENS)). 1. In the Model Browser, right-click on Component and select Show from the context menu. 2. Hide the CYLINDER_HEAD component by clicking the Elements icon next to it in the Model Browser. Tip: View1, A predefined visualization option, is included with this model under View in the Model Browser. Click on the monitor shaped icon next to View1; this loads a predefined view in the Model Browser allowing you to view all four bolts in the YZ plane. Two bolts have disc-shaped sections cut-off along its length. These bolts are then reconnected using 1D beam elements (CBEAM) and two rigid spiders (RBE2) per bolt. 1D pretensioning can now be applied to these two bolts. 3D pretensioning requires the creation of a surface at which pretensioning forces can be applied.

Figure 339: Using the predefined visualization option View1

A surface PT_Surf has been predefined to demonstrate 3D pretensioning on existing surfaces. To additionally demonstrate 3D pretensioning by creating a new surface, the fourth bolt is left unchanged.

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Figure 340: Bolt Pretensioning for this Tutorial Model

3. From the menu bar, click Tools > Pretension Manager to access the Pretension Manager. 4. Click on Add 1D Bolts and select the two 1D beam elements in bolts 1 and 2 (Figure 18). Tip: Care must be taken not to use CTRL+left mouse click while zooming in and positioning the elements in the graphics area for selection. Using CTRL+left mouse click can lead to the model being rotated about an axis and thus disengaging from the Y-Z plane of View1. It is recommended to only use CTRL+right mouse click (dragging action) while working in View1.

Figure 341: Selecting the Predefined 1D Elements for Pretensioning

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5. Select both fields under the Load Type column in the Pretension Manager window (Click on the first field and then while holding down the CTRL key, click on the second field). Click on the downward facing arrow next to the second field and select Force from the drop-down menu. 6. In a similar fashion, enter 4500.0 for both bolts in the Load Magnitude column.

7. Click Apply. A pretensioning force of 4500.0 N is applied to both 1D bolts, as shown in Figure 19.

Figure 342: Pretensioning Force is Applied to 1D Elements (PTFORCE=4500 N)

8. Click on Add 3D Bolts and select Select Existing Surface from the drop-down menu. 9. Click on the Wireframe elements skin only icon

to view the predefined contact surface PT_Surf

on the third bolt. Tip: If the predefined surface is not visible, then switch on (show) the PT_Surf entry in the Model Browser by clicking on the

icon next to it.

10. Click on the displayed predefined surface in the bolt, as shown in Figure 20 and click proceed.

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Figure 343: Selecting the Predefined PT_Surf Surface

11. Select Force under the Load Type column and enter 4500.0N for the Load Magnitude column and click Apply. A pretensioning force of 4500.0 N is applied normal to the PT_Surf surface, as shown in Figure 21.

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Figure 344: Applying a pretensioning force of 4500 N to the predefined surface PT_Surf on the third bolt

12. Click on Add 3D Bolts and select Create New Surface from the drop-down menu. 13. Utilize the click and drag technique (while holding down the shift key) described previously to select the top of the fourth bolt, as shown in Figure 22.

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Figure 345: Creating a New Surface for Pretensioning

14. Click on nodes in the panel below the graphics area and select all the nodes in the surface perpendicular to the Y-Z plane, as shown in Figure 23. The same click and drag technique can be used to select these nodes (draw a window encompassing the line as the perpendicular surface is a line in the Y-Z plane).

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Figure 346: Selecting the nodes necessary to create a pretensioning surface

15. Click create > return to return to the Pretension Manager. 16. Select Force under the Load Type column and enter 4500.0 N for the Load Magnitude and click Apply.

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Figure 347: Pretension Manager with all Four Pretensioned Bolts

17. Click OK in the Pretension Manager to view all four bolts with their respective pretensioning forces, as shown in Figure 25.

Figure 348: Reviewing the Four Pretensioned Bolts

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Creating a Pretension Loadstep and Subsequent Analysis Loadstep OptiStruct nonlinear quasi-static analysis loadsteps will be created for both pretensioning and the subsequent analysis. The analysis is nonlinear due to the presence of contact elements and the gasket loading/unloading paths. The CNTNLSUB Bulk Data Entry is used to continue the subsequent nonlinear analysis after pretensioning. Also, the pretensioning subcase is referenced in the analysis subcase using STATSUB(PRETENS). The Loadsteps Browser will be used to created the loadsteps and assign respective data entries. 1. Click on the Shaded Elements and Mesh Lines icon

next to the BLOCK and

CYLINDER_HEAD components in the Model Browser to show the hidden components. 2. Click Tools > Load Step Browser to access the Loadsteps Browser. 3. Right-click on Loadsteps in the Loadsteps Browser and select New loadstep. 4. In the Loadstep name: field, enter Pretension and click Create.

Figure 349: Creating the Pretension Subcase

5. Select Nonlinear quasi-static from the drop-down menu next to Loadstep type: in the Loadstep Type tab. 6. Switch to the Load References tab and click on NLPARM in the list of subcase entries. 7. Click on Nlparm in the Available nonlinear parameters: section and then click on the right facing arrow

to add it to the selected nonlinear parameter: section.

8. Similarly, click on SPC in the Subcase Entry list and add the Available SPC constraint to the Selected SPC constraints: section. 9. Follow the instructions in Steps 6 or 7 to add PRETENS_1 to the list from the PRETENSION Subcase Entry section. 10. Click OK after all three subcase entries are added to the Pretension loadstep. 11. Right-click on Loadsteps in the Loadsteps Browser and select New loadstep. 12. In the Loadstep name: field, enter Pressure and click Create.

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Figure 350: Creating the Pressure Loadstep

13. Select Nonlinear Quasi-static from the drop-down menu next to Loadstep type: in the Loadstep Type tab. 14. Switch to the Load References tab and click on NLPARM in the list of subcase entries. 15. Click on Nlparm in the Available nonlinear parameters: section and then click on the right facing arrow

to add it to the selected nonlinear parameter: section.

16. Similarly, click on SPC in the subcase entry list and add the Available SPC constraint to the Selected SPC constraints: section. 17. Follow the instructions in Steps 6 or 7 to add PRETENSION to the list from the STATSUB(PRETENS) subcase entry section. 18. Again, follow the instructions in Steps 6 or 7 to add PRESSURES to the list from the LOAD subcase entry section. 19. Click on the CNTNLSUB subcase entry and check the box next to CNTNLSUB, additionally select YES rom the pull-down menu next to CNTNLSUB. 20. Click OK after all five subcase entries are added to the Pressure loadstep. 21. Click Close to exit the Load Step Browser.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 351: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Pretension for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the Pretension.fem was written. The Pretension.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results 1. When the message Process completed successfully is received in the command window, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Click Close to close the message window, if one appears. 3. Click the Contour toolbar icon

.

4. Select the first pull-down menu below Result type: and select Displacement(v).

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Figure 352: Contour plot panel in HyperView

5. Click Apply, select Subcase 2 (Pressure) from the Results Browser. A contour plot of displacements is created, as shown in Figure 29. The cylinder head is hidden to view the displacement plots for the head bolts.

Figure 353: Displacement Contour for the Pressure Subcase after Pretensioning

In Figure 29, the displacement plot after running the pressure subcases can be seen. The maximum displacement is around 0.089 mm and it occurs in the region near the pretensioned bolt heads. 6. Select Gasket Thickness-direction Pressure in the Contour panel and click Apply. A contour plot of gasket pressure in the thickness direction is created, as shown in Figure 30. The other components are hidden to be able to better view the pressure variation on the gasket.

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Figure 354: Gasket pressure in the thickness direction for the Pressure subcase

Checkpoint The maximum pressure on the Gasket in the thickness direction is equal to 0.21 MPa.

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OS-T: 1392 Node-to-Surface vs Surface-to-Surface Contact This tutorial demonstrates how to set up contact between two parts and the impact of using choosing node-to-surface (N2S) versus surface-to-surface (S2S). In addition, this tutorial covers how to review the internally created CGAPG elements in case of N2S, and the nodes in contact in case of S2S. The model consists of two cubes in contact and enforced displacement on the top compressing the structure.

Figure 355: Illustration of the Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the blocks_contact.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating Contact Surfaces The imported model already contains the material, the property, the boundary conditions and the loadstep. In this step, the contact surfaces and the interface are created. 1. In the Model Browser, right-click and select Expand All. 2. Right-click in the Model Browser and select Create > Contact Surface to create a contact surface.

Figure 356: Creating a Contact Surface from the Model Browser

3. For Name, enter bottom.

4. In the Model Browser, right-click on the component bottom under Component and select Isolate Only. 5. To add elements and their faces to the surface, select the bottom surface in the Contact Surface panel of the Model Browser and click on 0 Elements in the Entity State Browser. 6. Click Element to select elements from the Panel. Switch the selector to Solid faces, as this contact surface will be on solid elements.

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7. Click Elements and select all elements from the bottom part of the structure. 8. Select three nodes on the surface that are in contact with the top part. Make sure the three nodes are all part of one element. 9. Click return to finish. 10. Repeat steps 3 through 9 to create the top part.

Figure 357: Adding a Contact Surface

Creating the Contact Interface After defining the two contact surfaces you need to define that they are in contact and with which properties. A contact interface needs to be defined. 1. In the Model Browser, right-click and select Create > Contact. 2. For Name, enter top_to_bottom.

3. In the Model Browser, select the newly created Contact to modify the properties of the contact. 4. For TYPE, select SLIDE.

This will result in a frictionless contact.

5. To select the slave surface, click on the field next to Slave Entity IDs. The slave surface should be the finer side, in this case the bottom (refer to the User Guide). 6. Select the top for Master Entity IDs. 7. For DISCRET, select N2S. 8. Retain the default values in the remaining fields, for now.

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9. Click anywhere in the Model Browser to apply these changes.

Figure 358: Defining the Contact interface

Creating Output Requests In the final step of model preparation, you want to request contact related output, CONTF; which causes Contact Force, Contact Deformation, Contact Status and Contact Traction to be output. Also, CONTPRM,CONTGAP, CONTPRM,CONTGRID and GAPPRM,HMGAPST are used to review the created contact elements. 1. From the main menu, select Setup > Create > Control Cards. 2. Select GLOBAL_OUTPUT_REQUEST and CONTF.

Figure 359: Setting up a Global Output Request

3. In the next panel, select the settings to request contact related output, as shown below.

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Figure 360: Requesting Contact Related Output

4. Click return to complete the card definition. 5. Repeat the steps above to create the CONTGAP and CONTGRID cards, as seen in Figure 361. They are available under the CONTPRM control card.

6. Select UNSUPPORTED_CONTPRMS and enter 2. 7. Then create the following cards below.

a) CONTPRM,CONTGAP,YES (outputs the internally created CGAPG for N2S contact) b) CONTPRM,CONTGRID,YES (outputs a set containing the grids in S2S contact)

8. Click return.

Figure 361: Defining CONTPRM cards CONTGAP and CONTGRID

9. Click Next to locate the GAPPRM control card and click HMGAPST. 10. Set the VALUE to YES. Outputs the open/closed status of the CGAPG elements.

Figure 362: Defining GAPPRM card HMGAPST

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 363: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Contact_N2S for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the Contact_N2S.fem was written. The Contact_N2S.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Submitting a Job for S2S 1. In the Model Browser, select the top_to_bottom card under Group. 2. Set DISCRET to S2S. 3. Repeat the steps in Submitting the Job, with the new file name Contact_S2S.fem.

Viewing the Results Displacements, Element Stresses, Contact Force, Contact Deformation, Contact Status and Contact Traction are calculated and can be plotted using the Contour panel in HyperView. Only compare the Contact Traction between the N2S and the S2S run.

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Comparing the Contact Traction 1. When the message Process completed successfully is received in the command window, click HyperView. HyperView is launched and the results are loaded for the S2S run. A message window appears to verify that the model and result files are loading into HyperView. 2. Click Close to close the message window, if one appears. 3. Select the page window layout icon

to split the page into two windows.

4. Load the other model in the new window by clicking 5. Click the Contour toolbar icon

and selecting contact_N2S.h3d.

in one of the two windows.

6. For Result type, select Contact Traction/Normal(s). 7. Click Apply.

Figure 364: Contour Plot Panel in HyperView

8. In the Model Browser, unselect the top part of the structure. Only the results on the contact surface are visible.

Figure 365: Isolating the Bottom Part of the Structure in HyperView

9. Right-click in the window that shows the contour and select Apply Style > Current Page > All selected to view the same results for both models. A contour plot of normal contact traction shows for both runs. The traction for the S2S run is much more uniform than for N2S by comparing the maximum and minimum values.

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Figure 366: Applying the Setup in One Window to the Rest of the Page

Figure 367: Contour of the Normal Contact Traction for S2S on the Left and N2S on the Right

Reviewing the Internally Created CGAPC Elements After viewing the contact traction in HyperView, check the internally created contact elements for the N2S. 1. Repeat Steps 1.1 through 1.4. 2. Select the Contact_N2S.fem file, located in the folder selected in Step 1.4.

3. Import the internally created CGAPG elements by importing the file contact_N2S.contgap.fem. 4. Right-click on the component Gaps from CONTACT1 in the Model Browser to review the gap elements. 5. Select isolate only to visualize the elements better. 6. Click

to turn on the element tags.

7. Click File > Run > Command File to create element sets to identify the open/closed status of the elements at the end of the run.

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8. Select the file contact_N2S.HM.gapstat.tcl.

9. Run a command file in HyperMesh to create sets containing open and closed gaps. 10. To see which gaps are closed or open at the end of the simulation, review the element sets that were created. Review the set OS_gaps_sub_001_closed by selecting it in the Model Browser and clicking on the field next to Entity IDs in the Entity State Browser. This shows that all gaps are closed, as it contains all elements. If there were some open gaps, another set OS_gaps_sub_001_open would have been created, as well.

Figure 368: Reviewing the Closed Gaps at the End of the Analysis

Reviewing the Grids The contact for S2S contact is different from N2S in the sense that no CGAPG elements are created internally. This means the process in Step 8 cannot be applied to S2S contacts. However, you can review the master and slave grids that are being used in the S2S contact, to ensure that the contact has been established in the correct manner. 1. Repeat Steps 1.1 through 1.4. 2. Select the Contact_S2S.fem file, located in the folder selected in Step 1.4.

3. Import the grid set that show the grids where S2S contact has been established by importing the file contact_S2S.contgrid.fem.

4. Right-click on the component bottom in the Model Browser and select isolate only to review the grids. 5. Select Tools > Set Browser. The Set browser opens. 6. In the Set browser, right-click on the set ^SlaveGrids_Contact_#1 and select Show.

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Contact has been established on the entire surface as expected.

Figure 369: Reviewing the Slave Nodes of the S2S Contact

7. Repeat the steps in Reviewing the Internally Created CGAPC Elements for the component top and the set ^MasterGrids_Contact_#1.

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Reviewing the Contact Status The contact status for both N2S and S2S can also be reviewed in HyperView, if the model contained the contact result output request CONTF. To view this, repeat the steps in Comparing the Contact Traction while choosing Contact Status/Normal(s) as the contour plot.

Figure 370: Reviewing the Contact Status in HyperView as a Contour Plot

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OS-T: 1393 Basics of Contact Properties and Debugging This tutorial demonstrates the effect of using contact stabilization, clearance, adjust and smoothing. The model consists of two circular parts where the inner one is heated and the outer one cooled down, leading to contact between the two. The effect of using several important contact settings such as contact stabilization, clearance, adjust and smoothing on both the results and the convergence behavior is considered. The model consists of two circular parts where the inner one is heated and the outer one cooled down, leading to contact between the two. The effect of using several important contact settings such as contact stabilization, clearance, adjust and smoothing on both the results and the convergence behavior is considered.

Figure 371: Illustration of the Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the wheels_contact.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating a PCONT Property The imported model already contains the material, the property, the boundary conditions and the loadstep, the contact surfaces and the Contact. In this step, a PCONT property is created. 1. In the Model Browser, right-click and select Expand All. 2. Right-click in the Model Browser, and select Create > Property to create a PCONT property. 3. For Name, enter cont_prop.

4. Open the Entity Editor by selecting the newly created property in the Model Browser. 5. In the Entity Editor, change the Card Image to PCONT.

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Figure 372: Changing the PCONT Contact Property

6. In the Model Browser, select the interface cont_interf to assign the property to the interface. 7. In the Entity Editor, select Property Id as the property and change the PID to cont_prop.

Submitting the Job 1. From the Analysis page, enter the OptiStruct panel.

Figure 373: Accessing the OptiStruct Panel

2. Click save as following the input file field. The Save As dialog opens. 3. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, Contact_S2S.fem, in the File name field. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The name and location of the Contact_S2S.fem file displays in the input file field.

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5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct. This launches the OptiStruct job. If the job is successful, the new results files should be in the directory from which Contact.fem was selected. The Contact_S2S.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Adding Contact Stabilization Since the non-linearity of this model is only due to contact, a good way to overcome the convergence issues is to add contact stabilization. This will especially be useful when part of the structure is held in place by the contact, which is the case here. 1. Click Setup > Create > Control Cards. 2. Select PARAM and check the box next to EXPERTNL. 3. Select CNTSTB. Also, contact stabilization can be activated through the Bulk Data card CNTSTB and referencing it from within the subcase. This gives you more options. 4. Repeat Submitting the Job, with the new file name Contact_CNTSTB.fem.

Figure 374: Creating PARAM,EXPERTNL,CNTSTB

Adding Clearance Now you want to investigate the influence of clearance on the model. 1. In the Model Browser, select the cont_prop property. 2. In the Entity Editor, click on the field next to CLEARANCE and enter the value 0.1.

Clearance will internally set the gap between the surfaces to the real value chosen, independently of the actual position of the grids, if grids are not moved to achieve this.

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Figure 375: Changing the PCONT Contact Property

3. Repeat Submitting the Job, with the new file name Contact_Clearance.fem.

Adding AUTO Adjust Now you want to investigate the influence of adjust on the model. First, remove the clearance you defined in Adding Clearance. 1. In the Model Browser, select the property cont_prop. 2. In the Entity Editor, click on the field next to CLEARANCE and remove the previously inserted value of 0.1. 3. In the Model Browser, select the interface cont_interf.

4. In the Entity Editor, click on the field next to ADJUST and select AUTO.

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Figure 376: Changing the Parameters of the CONTACT

5. Repeat Adding Clearance, with renaming the file Contact_Adjust.fem.

Applying Surface Smoothing 1. In the Model Browser, select the interface cont_interf. 2. In the Entity Editor, click on the field next to ADJUST and set to blank. 3. For CONTACT_NUM_SMOOTH, enter 1.

4. Click on the field next to SMSIDE and select BOTH and ALL.

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Figure 377: Selecting the Surface Smoothing Option on the CONTACT Card

5. Repeat Submitting the Job, with the file name Contact_Smoothing.fem.

Viewing the Results Displacements, Element Stresses, Contact Force, Contact Deformation, Contact Status and Contact Traction are calculated and can be plotted using the Contour panel in HyperView. Only compare the Contact Traction between the N2S and the S2S run.

Comparing the Contact Traction 1. Launch HyperView. 2. Select the page window layout icon 3. Click

to split the page into four windows.

to load the first model in one of the window.

4. Select Contact_CNTSTB.h3d for model and results. 5. Click Apply.

6. Do the same in the other three windows for Contact_Clearance.h3d, Contact_Adjust.h3d and Contact_Smoothing.h3d. 7. Click the Contour toolbar icon

in one of the four windows.

8. For Result type, select Contact Traction/Normal(s). 9. Click Apply.

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Figure 378: Contour Plot Panel in HyperView

10. In the Entity Editor, unselect the outer part of the structure. Only the results on the contact surface will be visible. 11. Right-click in the window that shows the contour and select Apply Style > Current Page > All selected to view the same results for both models. 12. A contour plot of normal contact traction shows for both runs. The traction for the runs with clearance and adjust are more uniform than they are for the model with stabilization only. The surface smoothing leads to a more uniform contour. In addition, the peaks are much lower for these three models. The reason why is, the traction is much higher for adjust than it is for the clearance, and the adjust run is that for adjust, the gap is closed initially, which leaves less room for stress free thermal expansion as for the other runs.

Figure 379: Applying the Setup in One Window to the Rest of the Page

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Figure 380: Normal Contact Traction Contour for the Four Different Runs

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Large Displacement Finite Element Analysis Large Displacement Finite Element Analysis

This chapter covers the following: •

OS-T: 1500 Nonlinear Implicit Analysis of Bending of a Plate (p. 400)

•

OS-T: 1510 Follower Loads, Nonlinear Adaptive Criteria, and Nonlinear Intermediate Results (p. 413)

•

OS-T: 1520 Finite Sliding of Rack and Pinion Gear Model (p. 428)

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OS-T: 1500 Nonlinear Implicit Analysis of Bending of a Plate This tutorial demonstrates nonlinear large displacement analysis in OptiStruct by simulating the bending of a plate under constant pressure. A comparison with linear analysis results is also provided to illustrate the requirement of conducting a nonlinear large displacement analysis. This tutorial considers nonlinear geometric effects (large displacements) and elastoplastic material. For static analysis, the energy equation reduces to F=Ku, wherein we solve for the unknown displacements (u). In Nonlinear Large Displacement analysis, the stiffness (K) may be a function of material, geometry, and boundary conditions. Therefore, an incremental-iterative approach is utilized to calculate the unknown displacements. Therefore, it is possible to understand which conditions are considered in a linear analysis. First, the material behavior is considered linear during the analysis, . Second, the geometry deformation should be small enough that the initial shape is not changed significantly enough to affect the stiffness. Finally, the boundary conditions should not vary during the analysis.

Figure 381:

The analysis considers both geometric and material nonlinearity. The geometric nonlinearity is considered because of the large displacements observed in the geometry, . Besides, the resultant stress exceeds the yield stress limit, which implies that material does not conform to a linear stress-strain behavior and plastic effects begin to be observed.

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Model Description Figure 382 illustrates the structural model used for this tutorial: a long rectangular plate which is supported at two ends and distributed load is applied on the top surface. The dimensions of the plate and material parameters can be obtained, as shown below.

Figure 382: Representation of Constraints and Pressure Load on the Plate

Units

Length: mm Time: s Mass: ton Force: N Stress: MPa

Length

1000 mm

Width

200 mm

Thickness

4.0 mm

Material

Steel, elastoplastic Initial Density 3 7.86e-9 kg/mm Young's modulus (E) 200000 MPa Poisson coefficient 0.29 Yield stress 100.0 MPa Tangent modulus 20000.0 MPa

Imposed pressure

0.02 MPa, applied normal to the plate

The following exercises are included in this tutorial:

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• Create plastic material and corresponding shell property • Set up boundary conditions and imposed load • Set up nonlinear and linear analysis • Submit job and view results

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the plate.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Update Material 1. In the Model Browser, click on the material MAT1_1. 2. Input the values, as shown below. Refer to MAT1 for more information. Initially, the MAT1 card image represents a linear isotropic material.

3. Check the box next to MATS1 to define additional material properties for a bilinear material elastoplastic for nonlinear analysis. LIM1 is the material yield point, in this case, the yield stress.

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H is the plasticity modulus (work hardening slope) that defines the linear relation between strain and stress in the plastic region. For a bilinear material curve, it is related to the Young’s modulus by the tangent modulus ( ). Refer to MATS1 for more information.

Figure 383: Young’s and Tangent Modulus in the Stress-Strain Curve and Equation that Correlates Them

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Figure 384:

Update Property 1. In the Model Browser, click on the property PSHELL_1. 2. Input the values, as shown below. Refer to PSHELL for more information.

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OptiStruct Tutorials Large Displacement Finite Element Analysis

Figure 385:

Create Boundary Conditions 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter LC_SPC.

3. Click Color and select a color from the color palette. 4. For Card Image, select None. 5. From the Analysis page, select constraints, toggle create. 6. Switch entity selector to nodes and select the nodes.

Figure 386:

7. Select the degrees of freedom dof1 and dof3. Deselect all others.

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8. For load types, select SPC. 9. Click create to create the boundary constraints. 10. Next, select the bottom two nodes, as shown below.

Figure 387:

11. Select the degrees of freedom dof1, dof3 and dof3. Deselect all others. This constrains translation movement in z direction. 12. For load types, select SPC. 13. Click create to create the boundary constraints. 14. Click return to go back to the main menu.

Create Uniform Pressure 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter LC_IMPLOAD.

3. Click Color and select a color from the color palette. 4. For Card Image, select None. 5. From the Analysis page, click pressures and toggle create. 6. Switch entity selector to elems and select all elements. 7. Click on the toggle next to magnitute= and switch pressure defintion method to constant vector. 8. For magnitude, enter -0.02.

9. For load types, select PLOAD as the load type. 10. Click create > return.

Define Nonlinear Analysis Parameters 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter LC_NLPARM.

3. For Card Image, select NLPARM. 4. Select the CONV as UPW with an EPSUP and ESPS of 0.001, and EPSW of 1e-7, that are the default values.

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CONV flag selects the convergence criteria. In this case, UPW is a combination of displacement (U), load (P) and work (W) criteria. EPSU, EPSP and EPSW are their respective error tolerances. 5. Input the values, as shown below. Refer to NLOUT for more information.

Figure 388:

Create Output Parameters Control 1. In the Model Browser, right-click and select Create > Load Collector. 2. For Name, enter LC_NLOUT.

3. For Card Image, select NLOUT. 4. Check the box next to NINT and enter 10. This parameter sets the number of intervals shown in output for intermediate results. 5. Input the values, as shown below. Refer to NLOUT for more information.

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Figure 389:

Define Output Control Parameters 1. From the Analysis page, select control cards. 2. Click GLOBAL_OUTPUT_REQUEST. 3. For DISPLACEMENT, ELFORCE, OLOAD, STRESS, and STRAIN, set Option to Yes. 4. Click return twice to go to the main menu.

Activate Large Displacement Nonlinear Analysis 1. From the Analysis page, select control cards. 2. From control cards, select PARAM. 3. Select HASHASSM and LGDISP. For nonlinear analysis, it is advisable to set HASHASSM card for reduction of the memory requirement, and set LGDISP for activation of large displacement nonlinear static analysis, according to the parameters specified in NLPARM Load Collector.

4. For HASHASSM, set Option to YES. 5. For LGDISP, set to 1.

6. Click return to go back to the main menu.

Create Nonlinear Static Analysis Subcase In this step, a linear and nonlinear load case are created, both with the same boundary conditions and imposed load.

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1. In the Model Browser, right-click and select Create > Load Step. 2. For Name, enter nonlinear_lgdisp.

3. For Analysis type, select Nonlinear quasi-static. 4. For SPC, select Unspecified > Loadcol. 5. In the Select Loadcol dialog, select LC_SPC from the list of load collectors and click OK. This sets the boundary condition created above. 6. For LOAD, select Unspecified > Loadcol. 7. In the Select Loadcol dialog, select LC_IMPLOAD from the list of load collectors and click OK. This sets the imposed load created above. 8. For NLPARM, select Unspecified > Loadcol. 9. In the Select Loadcol dialog, select LC_NLPARM from the list of load collectors and click OK. This sets the analysis parameters created above. 10. For NLOUT, select Unspecified > Loadcol. 11. In the Select Loadcol dialog, select LC_NLOUT from the list of load collectors and click OK. This sets the output control parameters created above. The nonlinear analysis has been set. 12. In the Model Browser, right-click and select Create > Load Step. 13. For Name, enter linear.

14. For Analysis type, select Linear Static. 15. For SPC, select Unspecified > Loadcol. 16. In the Select Loadcol dialog, select LC_SPC from the list of load collectors and click OK. 17. For LOAD, select Unspecified > Loadcol. 18. In the Select Loadcol dialog, select LC_IMPLOAD from the list of load collectors and click OK. The linear analysis has been set.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 390: Accessing the OptiStruct Panel

2. Click save as.

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3. In the Save As dialog, specify location to write the OptiStruct model file and enter plate for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the plate.fem was written. The plate.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: plate.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. plate.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. plate.h3d HyperView binary results file. plate.stat Summary, providing CPU information for each step during analysis process. In the output file (plate.out), it is possible to follow the convergence iterations that are calculated according to criteria parameters chosen in Define Nonlinear Analysis Parameters. Also, the maximum plastic strain is calculated for each step.

Figure 391:

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View the Results 1. Using HyperView, open the results file (plate.out) and plot the Displacement and the von Mises stress contour at 100% load (Load Factor=1.0) for subcase 1 and subcase 2. 2. Compare the results.

Figure 392: Displacement

Figure 393: Stress (von Mises)

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Figure 394: Plastic Strain

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OS-T: 1510 Follower Loads, Nonlinear Adaptive Criteria, and Nonlinear Intermediate Results This tutorial demonstrates how to setup Follower Loads, and the usage of Nonlinear Adaptive Criteria (NLADAPT) and how intermediate results can be requested for Nonlinear runs. You will see how the activation of Follower Loads leads to a significant difference in model behavior and results, and how inaccurate results may be output if the follower load mechanism is not taken into account. You will look at activation of Follower Loads that are concentrated forces (Beam model) and of Follower Loads that are pressures (Rubber Disk model).

Figure 395: Illustration of the Models: Follower Loads Concentrated Forces - Beam (left), Pressures - Rubber Disk Model (Right)

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Setting Up the Beam Model The beam model is a curved steel beam constructed with CHEXA elements. A Force of 100 N is applied to the top cross-section of the beam. The bottom of the beam is constrained by single point constraints (SPC).

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the beam_fllwer.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Submitting the Job without Follower Loads Activation The imported model already contains the material, the property, the boundary conditions, activation of large displacement, and the loadstep. In this step, you will run the model directly to generate results. 1. From the Analysis page, enter the OptiStruct panel.

Figure 396: Accessing the OptiStruct Panel

2. Click save as following the input file field. The Save As dialog opens. 3. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, beam_fllwer.fem, in the File name field. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save.

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The name and location of the beam_fllwer.fem file displays in the input file field.

5. Set the export options toggle to all.

6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct. This launches the OptiStruct job. If the job is successful, the new results files should be in the directory from which beam_fllwer.fem was selected. The beam_fllwer.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Setting Up the Model Activating Follower Loads Follower loads for concentrated forces do not depend on the area of the element face to whose grids they are applied. Therefore, the results will remain the same for any activation option chosen on either the FLLWER Bulk Data Entry or the PARAM,FLLWER entry. Since you only have one subcase, select the parameter PARAM,FLLWER to activate follower loading for this model. 1. In the Model Browser, Cards folder, click PARAM. The PARAM entry is displayed in the Entity Editor. 2. Activate the Follower Loads.

a) Check the box next to FLLWER. b) Set VALUE to 1. Options 1, 2, and 3 have the same effect for concentrated loads since element face areas are not involved. Using the parameter instead of the Bulk Entry activates follower loading for all subcases in a model. If you want to only activate follower loads for specific subcases, you can use FLLWER Bulk Data and Subcase entries.

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Figure 397:

Activating Nonlinear Adaptive Criteria Parameters that allow you to define Nonlinear Adaptive Criteria are available via the NLADAPT Bulk Data and Subcase entries. You can typically specify time-stepping and convergence criteria for Nonlinear Analysis if you run into convergence issues. Refer to the NCUTS parameter in this exercise. Similarly, you can define the DTMIN and DTMAX parameters, some of the other parameters like NOPCL and NSTSL are intended for models with contacts. 1. Create a load collector. a) In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. b) For Name, enter NLADAPT.

c) Set Card Image to NLADAPT. d) Check the box next to NCUTS, then enter 5 (default) in the VALUE field.

This indicates to OptiStruct that the maximum number of cutbacks allowed to reduce the time increment is 5. OptiStruct will error out if a greater number of cutbacks is required for a particular time increment for iterative convergence.

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Figure 398:

2. Edit the Nonlinear Static load step. a) In the Model Browser, Load Steps folder, click Nonlinear Static. The load step is displayed in the Entity Editor. b) For NLADAPT, click Unspecified > Loadcol. In the Select Loadcol dialog, select NLADAPT and click OK.

Figure 399:

Activating Nonlinear Intermediate Results Parameters that allow you to activate Nonlinear Intermediate Results are available via the NLOUT Bulk Data and Subcase entries. The number of intervals at which intermediate results are output is controlled by the NINT parameter. The SVNONCNV parameter can be used to activate/deactivate the output of results for non-convergent solutions. This is currently turned on by default (set to YES).

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1. Create a load collector. a) In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. b) For Name, enter NLOUT.

c) Set Card Image to NLOUT. d) Check the box next to NINT, then enter 10 (default) in the VALUE field.

This indicates to OptiStruct that the maximum number of intervals at which intermediate results are requested is 10. If the load increment from any load "n" to load "n+1" is greater than 1/NINT (in this case, 1/10 is 0.1), then the results corresponding to load level "n+1" are saved for output; otherwise, the results are not saved. Note: This parameter has no control over the adaptive load size selection during the incremental-iterative solution process. It only specifies the number of intervals when results are saved for output during the solution process.

2. Edit the Nonlinear Static load step. a) In the Model Browser, Load Steps folder, click Nonlinear Static. The load step is displayed in the Entity Editor. b) For NLOUT, click Unspecified > Loadcol. In the Select Loadcol dialog, select NLOUT and click OK.

Figure 400:

Submitting the Job with Follower Loads Activation The model now consists of loads which have been identified as follower loads. Additionally, you have learned how to activate adaptive criteria for nonlinear analysis, and request results at intermediate increments.

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1. From the Analysis page, enter the OptiStruct panel.

Figure 401: Accessing the OptiStruct Panel

2. Click save as following the input file field. The Save As dialog opens. 3. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, beam_fllwer_ON.fem, in the File name field. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The name and location of the beam_fllwer_ON.fem file displays in the input file field. 5. Set the export options toggle to all.

6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct. This launches the OptiStruct job. If the job is successful, the new results files should be in the directory from which beam_fllwer_ON.fem was selected. The beam_fllwer_ON.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Displacements and Element Stresses are calculated by default and can be plotted using the Contour panel in HyperView. Compare the displacement results between models without Follower Load activation. 1. Launch HyperView. 2. Click

to split the page into two windows.

3. Load the result files by clicking

and navigating to your working directory.

a) In the first window, load the beam_fllwer.h3d file.

b) In the second window, load the beam_fllwer_ON.h3d file.

4. Setup contouring for each window.

a) Click the window to activate it, then click

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b) Set Result type to Displacement (v). c) Click Apply. Note: Since you have requested results for intermediate iterations via NLOUT, you will see results for all intermediate iterations. 5. In the Results Browser, click Load Factor and select the final increment Load Factor = 1.000000E+00.

Figure 402:

The Displacement contour results display. You can see that the activation of follower forces has modified the displacement profile significantly.

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Figure 403:

Setting Up the Rubber Disk Model 2

The rubber disk model a rubber disk constructed with MATHE elements. A pressure load of 1 N/mm is applied to the rubber disk. The circumference of the disk is constrained via single point constraints (SPC).

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the disk_fllwer.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model

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Creating Follower Load Bulk Data Entries In the Beam model, the follower loads for concentrated forces do not depend on the area of the element face to whose grids they are applied. Therefore, the results will remain the same for any activation option chosen on either the FLLWER Bulk Data Entry or the PARAM,FLLWER entry. Additionally, since you only had one subcase, select the parameter PARAM,FLLWER to activate follower loading for this model. In this disk model, the loads are pressure loads which may depend on the area of the element faces to whom they are applied. Additionally, you have multiple subcases to showcase the effect of different FLLWER options. In the FLLWER Bulk Data Entry in the OptiStruct help, you will see the OPT parameter which contains the following options for the calculation of Follower Loads: = -1, 0

Follower force calculation is not activated.

= 1 (default)

Follower effect is activated. For pressure load, both element surface area and load direction are updated during the solution. For concentrated force, only the force direction is updated.

=2

Follower effect is activated. For pressure load, only element surface area is updated (load direction is not updated) during the solution. For concentrated force, only the force direction is involved; which is the same as OPT = 1.

=3

Follower effect is activated. For pressure load, only load direction is updated (element surface area is not updated). For concentrated force, only the force direction is updated; which is the same as OPT = 1.

1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter FLLWER_1.

3. Set Card Image to FLLWER. 4. Set OPT to 1.

Figure 404:

5. Create two more load collectors named FLLWER_2 and FLLWER_3.

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a) Set Card Image to FLLWER. b) Set OPT to 2 for FLLWER_2, and set OPT to 3 for FLLWER_3.

Referencing the FLLWER Bulk Entries The created FLLWER Bulk Data Entries should now be selected in the Subcase section. 1. Edit the fllwer_1 load step. a) In the Model Browser, Load Steps folder, click fllwer_1. The load step is displayed in the Entity Editor. b) Check the box next to FLLWER. c) For ID, click Unspecified > Loadcol. In the Select Loadcol dialog, select FLLWER_1 and click OK.

Figure 405:

2. Edit the fllwer_2 load step. a) In the Model Browser, Load Steps folder, click fllwer_2. The load step is displayed in the Entity Editor. b) Check the box next to FLLWER. c) For ID, click Unspecified > Loadcol. In the Select Loadcol dialog, select FLLWER_2 and click OK. 3. Edit the fllwer_3 load step. a) In the Model Browser, Load Steps folder, click fllwer_3. The load step is displayed in the Entity Editor. b) Check the box next to FLLWER. c) For ID, click Unspecified > Loadcol. In the Select Loadcol dialog, select FLLWER_3 and click OK.

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Activating Nonlinear Intermediate Results Parameters that allow you to activate Nonlinear Intermediate Results are available via the NLOUT Bulk Data and Subcase Entries. The number of intervals at which intermediate results are output is controlled by the NINT parameter. The SVNONCNV parameter can be used to activate/deactivate the output of results for non-convergent solutions. This is currently turned on by default (set to YES). 1. Create a load collector. a) In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. b) For Name, enter NLOUT.

c) Set Card Image to NLOUT. d) Check the box next to NINT, then enter 10 (which is the default) in the VALUE field.

This indicates to OptiStruct that the maximum number of intervals at which intermediate results are requested is 10. If the load increment from any load "n" to load "n+1" is greater than 1/NINT (in this case, 1/10 is 0.1), then the results corresponding to load level "n+1" are saved for output; otherwise, the results are not saved. Note: This parameter has no control over the adaptive load size selection during the incremental-iterative solution process. It only specifies the number of intervals when results are saved for output during the solution process.

Figure 406:

2. Edit the fllwer_1 load step. a) In the Model Browser, Load Steps folder, click fllwer_1. The load step is displayed in the Entity Editor. b) For NLOUT, click Unspecified > Loadcol. In the Select Loadcol dialog, select NLOUT and click OK.

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Figure 407:

3. Edit the fllwer_2, fllwer_3, and NO_fllwer load steps. a) In the Model Browser, Load Steps folder, click the load step to edit. The load step is displayed in the Entity Editor. b) For NLOUT, click Unspecified > Loadcol. In the Select Loadcol dialog, select NLOUT and click OK.

Submitting the Job with the Disk Model The model now consists of loads which have been identified as follower loads. Additionally, you have learned how to request results at intermediate increments. 1. From the Analysis page, enter the OptiStruct panel.

Figure 408: Accessing the OptiStruct Panel

2. Click save as following the input file field. The Save As dialog opens.

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3. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, disk_fllwer.fem, in the File name field. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The name and location of the disk_fllwer.fem file displays in the input file field. 5. Set the export options toggle to all.

6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct. This launches the OptiStruct job. If the job is successful, the new results files should be in the directory from which disk_fllwer.fem was selected. The disk_fllwer_ON.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Displacements and element stresses are calculated by default and can be plotted using the Contour panel in HyperView. Compare the displacement results between models with and without Follower Load activation. 1. Launch HyperView. 2. Click

to split the page into two windows.

3. Load results from Subcase 1 to the first window. a) Click the first window to activate it. b) Load the results file by clicking file and click Apply.

. In the panel area, load the disk_fllwer_ON.h3d result

c) In the Results Browser, select Subcase 1 (fllwer_1) and Load Factor = 1.000000E+00.

Figure 409:

4. Load results from the remaining subcases. a) Activate the second window and load the disk_fllwer_ON.h3d result file. In the Results Browser, select Subcase 2 (fllwer_2).

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b) Activate the third window and load the disk_fllwer_ON.h3d result file. In the Results Browser, select Subcase 2 (fllwer_3). c) Activate the fourth window and load the disk_fllwer_ON.h3d result file. In the Results Browser, select Subcase 2 (NO_fllwer). 5. Setup contouring for each window. a) Click the window to activate it, then click

on the toolbar.

b) Set Result type to Displacement (v). c) Click Apply. Note: Since you have requested results for intermediate iterations via NLOUT, you will see results for all intermediate iterations. The Displacement contour results display. You can see that the activation of follower forces has modified the displacement profile significantly. Additionally, you can see that since subcase 3 (OPT=3) updates the load direction but not the area, the force (Pressure*Area) distribution at the grid points is low for Subcase 3 and the Displacement results reflect this when compared to OPT=1 and 2.

Figure 410:

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OS-T: 1520 Finite Sliding of Rack and Pinion Gear Model This tutorial outlines the procedure to perform finite sliding analysis on a rack and pinion gear model. The circular gear is called the pinion and it engages teeth on the linear bar called the rack.

Figure 411: Model Circular Gear and Rack

Finite Sliding vs Small Sliding Analysis In small sliding analysis, not only is the relative sliding between master and slave relatively small but the contact search is done only at the beginning of the simulation. While for finite sliding the contact search is updated for every increment of the analysis. In this case, as you can see, the circular gear has to be in contact with the entire rack over the course of the simulation, so contact status needs to be updated for every increment to capture the entire motion and hence finite sliding is necessary. This tutorial helps you to define finite sliding contact between the circular gear and rack. The gear is held fixed at the center in all dof while the rack is given displacement in x dof but constrained in all other dof. All constraints and enforced displacements have already been defined in model. Contact surfaces to define the slave and master surfaces are also pre-defined in the model. Contact stabilization has been defined for the contact to help stabilize any rigid body motion before contact gets established. A very tiny end-of-subcase stabilization also has been specified to overcome any temporary instabilities that may sometimes occur at end-of-analysis.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the finite_sliding.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The finite_sliding.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Reviewing Material Properties The imported model contains a large amount of pre-defined information which allows you to focus on the finite sliding section in this tutorial. All material and properties are pre-defined for the circular gear and rack. The material properties of steel are assigned to both components. 1. In the Model Browser, Materials folder, right-click on steel and select Card Edit from the context menu. 2. Verify that the values on the MAT1 bulk data entry for the material properties of steel are input as shown in Figure 412. Young's Modulus of Elasticity = 2.1 x 105 N/m2 Poisson's Ratio = 0.3

Figure 412:

3. Click return to complete the review.

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Tip: You can review, in a similar manner, the remaining pre-defined data entries, like properties and load collectors. The procedure for load collector review is not as straight forward as shown above in some cases; however, this has been thoroughly illustrated in various other tutorials for your benefit.

Reviewing Contact Surfaces and Generating Finite Sliding Contact

Figure 413: Contact Surface Panel

1. In the panel area, go to the Analysis page and click contactsurfs to review the already created contact surfaces. 2. Go to the solid faces subpanel. 3. Review the contact surface for rack. a) Click name. b) Select rack. c) Click review.

Figure 414: Review of Contact Surface for Rack

4. Review the contact surface for gear. 5. Click return to exit the contactsurfs panel. 6. Create a contact surface. a) Go to the interfaces panel, create subpanel.

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b) In the name = field, enter rack_pinion for the interface. c) Click type= > CONTACT. d) Click create. e) Go to the add subpanel to choose the master and slave surfaces for the rack_pinionfor interface. f) For both the master and slave, change the entity type to csurfs. g) Using the contactsurfs selector, select the rack contact surface for the slave and the gear contact surface for the master.

Figure 415: Selecting Master and Slave Surfaces

h) Click update. 7. To review the interface, click review.

Figure 416: Reviewing Interface

8. Edit the contact surface. a) Go to the card image subpanel. b) Click edit to edit the contact interface. c) Set TYPE to SLIDE. d) Set DISCRET to S2S. e) Set TRACK to FINITE. Surface-to-surface a finite sliding contact without friction have been defined.

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Figure 417: S2S, Finite Sliding Contact Definition

9. Click return to exit the interfaces panel. The finite sliding contact definition is now complete.

Reviewing Parameters, Contact Output Request and Loadstep Definition Large displacement formulation needs to be activated for finite sliding contact. 1. Click on control cards panel to review the parameter and turn on LGDISP. 2. Click next twice and select PARAM. 3. Verify PARAM, LGDISP is set to1. 4. Click return. 5. Click GLOBAL_OUTPUT_REQUEST. 6. Verify CONTF is selected. Note: CONTF gives contact output results, like contact pressure, gap penetration, sliding distance, and so on. 7. Click return twice to exit the control card panel. 8. Click the loadsteps panel to review the pre-defined loadstep. The SPC and NLPARM loads have been defined and analysis should be of type nonlinear quasistatic. The SPC load points to the fixed constraints on the circular gear, as well as enforced displacement on the bottom of rack. The NLPARM load defines the nonlinear parameters.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 418: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rack_pinion for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the rack_pinion.fem was written. The rack_pinion.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Displacements, Element stresses, Contact forces, contact deformation, and so on are calculated and can be plotted using the Contour panel in HyperView. 1. Once you receive the message Process completed successfully in the command window, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform you of the successful model and result files loading into HyperView. 2. Click Close to exit the message window, if one appears. 3. On the toolbar, click

(Contour).

4. Under Result type, from the first drop-down menu, select Element Stresses (2D & 3D)(t).

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Figure 419: Contour Plot Panel in HyperView

5. Select Load Factor = 3.369662E-01 and click Apply. A contour plot of stresses is created. The load factor here denotes the % of load that has been applied.

Figure 420: Stress Contour at Load Factor = 3.3696 E-1 The stresses in rack and gear after 33.36% of load has been applied

6. Similarly, you can change the load factor and observe the changes in stresses on the rack and gear.

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Figure 421: Stress Contour at Load Factor = 8.74E-1 For load factor, if below 0.874, the contact at this point of time is between a very small area of the rack and gear tooth and hence stresses are higher

7. Optional: Animate the results using the Set Transient Animation Mode in HyperView.

Figure 422:

8. Optional: Select other result types in the Contour panel and click Apply.

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Fluid-Structure Interaction Analysis Fluid-Structure Interaction Analysis

This chapter covers the following: •

OS-T: 1600 Fluid-Structure Interaction Analysis of Piezoelectric Harvester Assembly (p. 437)

•

OS-T: 1610 Thermal Fluid-Structure Interaction Analysis on a Manifold (p. 449)

7

OptiStruct Tutorials Fluid-Structure Interaction Analysis

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OS-T: 1600 Fluid-Structure Interaction Analysis of Piezoelectric Harvester Assembly The purpose of this tutorial is to demonstrate how to carry out Fluid-Structure Interaction analysis that is, with OptiStruct nonlinear transient analysis coupling within AcuSolve fluid dynamic analysis. In this tutorial, you will explore the possibility of using piezoelectric based fluid flow energy harvesters. These harvesters are self-excited and self-sustained in the sense that they can be used in steady uniform flows. The configuration consists of a piezoelectric cantilever beam with a cylindrical tip body (which is the structure model) which promotes sustainable, aero-elastic structural vibrations induced by vortex shedding and galloping. The structural and aerodynamic properties of the harvester alter the vibration amplitude and frequency of the piezoelectric beam and the fluid flow. As you may know, the Piezoelectric energy harvesting using fluid flow involves the mutual interaction of three distinct dynamic systems, namely the fluid, the structure and the associated electrical circuit. Note: This tutorial is limited to study only fluid and the structure domain. Figure 424 illustrates the fluid structural model used for this tutorial: the dimensions of the beam are shown in Figure 423 and Figure 424.

Figure 423: Schematic of the Problem

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Figure 424: Various Layers of Beam

The AcuSolve fluid model (slab_dcfsi.inp) and the OptiStruct structural beam model (Slab.fem) are located in the fsi_models.zip file. Refer to Accessing the Model Files.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the Slab.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Creating Contact Surface 1. In the Model Browser, right-click and select Create > Contact Surface from the context menu. A default contact surface template displays in the Entity Editor. 2. For Name, enter FSI_Interaction_Surf.

3. Click Color and select a color from the color palette. 4. For Card Image, select SURF. 5. For Elements, click 0 elements > elements and pick all the faces of the beam.

Figure 425: All sides of the beam except in the front

6. Click add to add the faces to the contact surface. 7. Click return to exit from this panel.

Defining Nonlinear Parameters 1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter NLPARM_Card.

3. Click Color and select a color from the color palette.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis 4. For Card Image, select NLPARM. 5. Input the values, as shown in Figure 426. See NLPARM Bulk Data Entry for more information.

Figure 426:

Defining Transient Time Step Parameters 1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter TSTEP_Card.

3. For Card Image, select TSTEP. 4. For TSTEP NUM, enter 1. 5. Click

and input the values, as shown in Figure 427.

See NLPARM Bulk Data Entry for more information.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

Figure 427:

6. Click Close to finish.

Defining Incremental Result Output for Nonlinear Analysis 1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter NLOUT101.

3. Click Color and select a color from the color palette. 4. For Card Image, select NLOUT. 5. Input the values, as shown in Figure 428. See NLPARM Bulk Data Entry for more information.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

Figure 428:

Defining Fluid-Structure Interaction Parameters 1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter FSI100.

3. Click Color and select a color from the color palette. 4. For Card Image, select FSI. 5. Input the values, as shown in Figure 429. See NLPARM Bulk Data Entry for more information.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

Figure 429:

Define Output Control Parameters 1. From the Analysis page, select control cards. 2. Click GLOBAL_OUTPUT_REQUEST. 3. For DISPLACEMENT, ELFORCE, OLOAD, STRESS, and STRAIN, set Option to Yes. 4. Click return twice to go to the main menu.

Creating Nonlinear Transient Analysis Subcase 1. In the Model Browser, right-click and select Create > Load Step from the context menu. 2. For Name, enter FSI.

3. Click Color and select a color from the color palette. 4. For Analysis type, select Nonlinear transient. 5. Input/Select the Load Collector.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

Figure 430:

6. Reference the NLOUT Bulk Data Entry as a SUBCASE_UNSUPPORTED entry as:

Figure 431:

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 432: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Slab for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the Slab.fem was written. The Slab.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Initiating a Run 1. Launch the HyperWorks Solver Run Manager and select the Slab.fem file. 2. Click Run.

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Figure 433:

Submitting the AcuSolve Job 1. Open the AcuSolve input file (slab_dcfsi.inp) in a text editor. 2. Change the socket_host parameter in the EXTERNAL_CODE block to your machines hostname and save the file.

Figure 434:

3. Open the AcuSolve Cmd Prompt application and enter the command: acuRun-pb slab_dcfsi -np 8.

Figure 435:

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If the job is successful, you will see new results files in the directory where HyperMeshwas invoked. The Slab.out file is where you will find error messages that will help you debug your input deck, if any errors are present. The default files that will be written to your directory are: cci.txt

Contains information pertaining to model progression. Logs regarding connection establishment, initial external code handshake and subsequent time step data in conjunction with exchange/stagger.

Slab.html

HTML report of the analysis, giving a summary of the problem formulation and the analysis results.

Slab.out

ASCII based output file of the model check run before the simulation begins and gives some basic information on the results of the run.

Slab.stat

Summary of analysis process, providing CPU information for each step during the process.

Slab.h3d

HyperView compressed binary results file.

Viewing the Results Using HyperView, plot the Displacement contour at 1.0 s.

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Figure 436:

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

p.449

OS-T: 1610 Thermal Fluid-Structure Interaction Analysis on a Manifold The purpose of this tutorial is to demonstrate how to carry out a Thermal Fluid-Structure Interaction analysis on an engine exhaust manifold with conjugate heat transfer and structural deformation. This example is an engine exhaust manifold with conjugate heat transfer and structural deformation. The structure is gray cast iron, initially at 300 K. The manifold outer surface has a convective heat 2 transfer coefficient of h = 6 W/m K at 300 K. The four inlets to the manifold are held at 500 K with air as the fluid at 5 m/s. AcuSolve passes heat fluxes to OptiStruct. OptiStruct passes the temperatures to AcuSolve. Note: This tutorial is limited to study fluid and thermal domain only. The AcuSolve Fluid model (FSI_AS_MANIFOLD.inp) and OptiStruct Structural beam model (FSI_OS_MANIFOLD.fem) files are in the tfsi_models.zip file. Refer to Accessing the Model Files.

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Figure 437: Fluid Structural Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the FSI_OS_MANIFOLD.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

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Setting Up the Model Creating Contact Surface 1. In the Model Browser, right-click and select Create > Contact Surface from the context menu. A default contact surface template displays in the Entity Editor. 2. For Name, enter FSI_Interaction_Surf.

3. Click Color and select a color from the color palette. 4. For Card Image, select SURF. 5. For Elements, click 0 elements > elements and pick all the internal faces. Tip: To pick all the elements in the internal face, use the brake angle of 30 degrees.

Figure 438:

6. Click add to add the faces to the contact surface. 7. Click return to exit from this panel.

Defining Fluid-Structure Interaction Parameters 1. In the Model Browser, right-click and select Create > Load Collector. A default load collector template displays in the Entity Editor. 2. For Name, enter FSI100.

3. Click Color and select a color from the color palette. 4. For Card Image, select FSI. 5. Input the values, as shown in Figure 439.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis See NLPARM Bulk Data Entry for more information.

Figure 439:

Define Output Control Parameters 1. From the Analysis page, select control cards. 2. Click GLOBAL_OUTPUT_REQUEST. 3. For THERMAL and FLUX, set Option to Yes. 4. Click return twice to go to the main menu.

Creating Transient Heat Transfer Analysis Subcase 1. In the Model Browser, right-click and select Create > Load Step from the context menu. 2. For Name, enter TFSI.

3. Click Color and select a color from the color palette. 4. For Analysis type, select Heat Transfer (transient). 5. Input/Select the Load Collector.

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OptiStruct Tutorials Fluid-Structure Interaction Analysis

Figure 440:

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 441: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter FSI_OS_MANIFOLD for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the FSI_OS_MANIFOLD.fem was written. The FSI_OS_MANIFOLD.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Initiating a Run 1. Launch the HyperWorks Solver Run Manager and select the FSI_OS_MANIFOLD.fem file. 2. Click Run.

Figure 442:

Submitting the AcuSolve Job 1. Open the AcuSolve input file (slab_dcfsi.inp) in a text editor. 2. Change the socket_host parameter in the EXTERNAL_CODE block to your machines hostname and save the file.

Figure 443:

3. Open the AcuSolve Cmd Prompt application and enter the command: acuRun-pb FSI_AS_MANIFOLD -np 8.

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Figure 444:

If the job is successful, you will see new results files in the directory where HyperMeshwas invoked. The FSI_OS_MANIFOLD.out file is where you will find error messages that will help you debug your input deck, if any errors are present. The default files that will be written to your directory are: cci.txt

Contains information pertaining to model progression. Logs regarding connection establishment, initial external code handshake and subsequent time step data in conjunction with exchange/stagger.

FSI_OS_MANIFOLD.html

HTML report of the analysis, giving a summary of the problem formulation and the analysis results.

FSI_OS_MANIFOLD.out

ASCII based output file of the model check run before the simulation begins and gives some basic information on the results of the run.

FSI_OS_MANIFOLD.stat

Summary of analysis process, providing CPU information for each step during the process.

FSI_OS_MANIFOLD.h3d

HyperView compressed binary results file.

Viewing the Results Using HyperView, plot the Displacement contour at 1.0 s.

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Figure 445:

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p.456

Multibody Dynamics Analysis Multibody Dynamics Analysis

This chapter covers the following: •

OS-T: 1900 Dynamic Analysis of a Three-body Model (p. 458)

•

OS-T: 1910 Dynamic Analysis of a Slider Crank with Flexible Connecting Rod (p. 469)

•

OS-T: 1920 Large Displacement Analysis of a Cantilever Beam (p. 485)

•

OS-T: 1930 Generating Flexible Body for use in MotionSolve (p. 495)

•

OS-T: 1940 MBD Rigid Contact (p. 501)

•

OS-T: 1950 Curve to Curve Constraint (p. 510)

•

OS-T: 1960 Defining Point to Deformable Curve Joint (p. 519)

8

OptiStruct Tutorials Multibody Dynamics Analysis

p.458

OS-T: 1900 Dynamic Analysis of a Three-body Model In this tutorial, dynamic analysis on a simple three rigid bodies model is performed using OptiStruct. The force of gravity acts along the global Y axis, and the system has one degree of freedom. This exercise includes the creation of PRBODY (rigid body definition), JOINT and boundary conditions in HyperMesh. An existing finite element model is used in this tutorial problem.

Figure 446: Rigid Bodies Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the 3bodies_dynamics.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The 3bodies_dynamics.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data. The model has three components and a few free nodes that will be used to create bodies and joints for the MBD model.

Setting Up the Model Creating PRBodies PRBODY is the Rigid Body Definition for Multibody Simulation. PRBODY defines a rigid body out of a list of finite element properties, elements and grid points. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. Define PRBODY for the body1 component. a) In the body= field, enter blue.

b) Click type= and select PRBODY. c) Using the props selector, select body1. d) Click create. 4. Define PROBDY for the body2 component. a) In the body= field, enter lime.

b) Click type= and select PRBODY. c) Using the props selector, select body2. d) Click create. 5. Define PROBDY for the body3 component. a) In the body= field, enter orange.

b) Click type= and select PRBODY. c) Using the props selector, select body3. d) Click create. 6. Click return.

Creating Joints You will create two revolute joints, one ball joint, and one universal joint to constrain the degrees of freedom, such that the remaining degree of freedom will be just 1. DOF = 3*6 - (5+5+4+3) = 1

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Removes translational dof

Removes rotational dof

Removes total number of dof

Revolute

3

2

5

Universal

3

1

4

Ball (Spherical)

3

0

3

Type of Joint

Figure 447: Joints in the Model

1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 3. Create the revolute joint at the lower right corner of body3. a) Set joint type to revolute. b) Select node ID 12319 as the first terminal and node ID 13158 as the second terminal.

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Tip: Nodes 12319 and 13158 are coincident. Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window. c) Select node ID 12910 as a node for first orientation. d) Click create. The vectors 12319 to 12910 define the axis of rotation of the revolute joint.

Figure 448:

4. Create the revolute joint at the lower left corner of body1. a) Select node ID 11115 as the first terminal and node ID 13159 as the second terminal. b) Select node ID 11706 as a node for first orientation. c) Click create. The vectors 11115 to 11706 define the axis of rotation of the revolute joint.

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Figure 449:

5. Create the universal joint between body3 and body2. a) Set joint type to universal. b) Select node ID 12330 as first terminal which belongs to body3, and select node ID 7589 as second terminal which belongs to body2. c) Select node ID 12921 as a node for first orientation, and select node ID 11944 as a node for second orientation. d) Click create. The vectors 12330 to 12921 define the first cross pin axis, and the vectors 7589 to 11944 define second cross pin axis.

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Figure 450:

6. Create a ball (spherical) joint between body1 and body2. a) Set joint type to ball. b) Select node ID 11104 as first terminal which belongs to body1, and select node ID 7578 as second terminal which belongs to body2. c) Click create.

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Figure 451: Ball Joint between body1 and body2

Applying Loads and Boundary Conditions The gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multi body simulation, is created in the following steps.

Creating Load Collectors In this step you will create the gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multibody simulation. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter gravity.

3. Click Color and select a color from the color palette. 4. Set Card Image to GRAV. 5. Input the values as illustrated below.

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Figure 452:

6. Create another load collector. a) For Name, enter SIM.

b) For Card Image, select MBSIM. c) Input the values as illustrated below.

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OptiStruct Tutorials Multibody Dynamics Analysis

Figure 453:

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Dynamic.

3. Set Analysis type to Multi-body dynamics. 4. Define MLOAD. a) For MLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select gravity and click OK. 5. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK.

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 454: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter 3bodies_dynamics_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the 3bodies_dynamics_complete.fem was written. The 3bodies_dynamics_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results In this step you will view the results in HyperView, which can be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multi-body system simulation, video and engineering data. 1. While in the OptiStruct panel of the Analysis page, click HyperView. a) Optional: If a window appears with a warning message, click OK. The path and file name for 3bodies_dynamics_complete.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data.

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The model and results are loaded in the current HyperView window. 2. Click

to open the Contour panel.

3. Under Results type, select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 455:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

Figure 456:

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OS-T: 1910 Dynamic Analysis of a Slider Crank with Flexible Connecting Rod In this tutorial you will work with a slider crank model, which consists of a rigid crank, a flexible connecting rod, and a rigid sliding block. The objective of this analysis is to determine the deformation and stress of a flexible connecting rod under the high speed motion of the system. This tutorial includes the creation of PRBODY (rigid body definition), PFBODY (flexible body definition), and JOINT in HyperMesh. An existing finite element model is used in this tutorial.

Figure 457:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the slider_crank.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The slider_crank.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating PRBodies PRBODY is the Rigid Body Definition for Multibody Simulation. PRBODY defines a rigid body out of a list of finite element properties, elements and grid points. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. Define PRBODY for the support component. a) In the body= field, enter support. b) Click type= and select PRBODY.

c) Using the props selector, select support. d) Click create. 4. Define PROBDY for the crank component. a) In the body= field, enter crank.

b) Click type= and select PRBODY. c) Using the props selector, select crank. d) Using the nodes selector, select the node (ID 25231) at the center of RBE2 spider between connecting rod and crank.

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Figure 458:

e) Click create. 5. Define PROBDY for the block component. a) In the body= field, enter block.

b) Click type= and select PRBODY. c) Using the props selector, select block. d) Using the nodes selector, select the node (ID 25232) at the center of RBE2 spider between connecting rod and block.

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Figure 459:

e) Click create. 6. Click return.

Creating Flex Bodies (PFBODY) PFBODY is the Flexible Body Definition for Multibody Simulation. PFBODY defines a flexible body out of a list of finite element properties, elements, and grid points. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter Rod.

4. Click type= and select PFBODY. 5. Using the props selector, select Rod. 6. Using the elems selector, select two RBE2 elements that are inside a hole on the connecting rod. Tip: You could also use 'elems by id' and input the IDs 18795 and 18796 to select the two RBE2 elements.

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Figure 460:

7. Set CMS Method to Craig-Bampton. 8. Toggle number of modes to nmodes=, and enter 10.

Figure 461:

9. Click create. 10. Click return.

Creating Joints You will create three revolute joints, one fixed joint, and one translational joint are created to constrain the degrees of freedom. Removes Translational dof

Removes Rotational dof

Removes Total Number of dof

Revolute

3

2

5

Fixed

3

3

6

Translational

2

3

5

Type of Joint

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Figure 462:

1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 3. Create the fixed joint between ground and support. a) Set joint type to fixed. b) Select node ID 25313 as first terminal and select node ID 25543 as second terminal. Tip: Nodes 25313 and 25543 are coincident. Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window. c) Click create.

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Figure 463:

4. Create the revolute joint between support and crank. a) Set joint type to revolute. b) Select node ID 25472 as first terminal and select node ID 15124 as second terminal. c) Set first orientation to coordinates, then enter x= 0.0, y= 0.0, z= 1.0. The z-axis will be the axis of rotation of revolute joint.

d) Click create.

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Figure 464:

5. Create the revolute joint between the crank and connecting rod. a) Set joint type to revolute. b) Select node ID 25229 as first terminal and select node ID 25231 as second terminal. c) Set first orientation to coordinates, then enter x= 0.0, y= 0.0, z= 1.0. The z-axis will be the axis of rotation of revolute joint.

d) Click create.

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Figure 465:

6. Create the revolute joint between the connecting rod and sliding block. a) Set joint type to revolute. b) Select node ID 25230 as first terminal and select node ID 25232 as second terminal. c) Set first orientation to coordinates, then enter x= 0.0, y= 0.0, z= 1.0. The z-axis will be the axis of rotation of revolute joint.

d) Click create.

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Figure 466:

7. Create the translational joint between the sliding block and ground. a) Set joint type to translational. b) Select node ID 14519 as first terminal and select node ID 25228 as second terminal. c) Set first orientation to coordinates, then enter x= 1.0, y= 0.0, z= 0.0. The x-axis will be the direction of translation.

d) Click create.

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Figure 467:

8. Click return.

Creating DTI, UNITS 1. From the menu bar, click Setup > Create > Control Cards to open the Control Cards panel. 2. Click DTI_UNITS. 3. Define the unit system, as shown in Figure 468.

Figure 468:

4. Click return twice to return to the main menu.

Creating Load Collectors In this step you will create the gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multibody simulation. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu.

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OptiStruct Tutorials Multibody Dynamics Analysis A default load collector displays in the Entity Editor. 2. For Name, enter SIM.

3. Click Color and select a color from the color palette. 4. Set Card Image to MBSIM. 5. Input the values as illustrated below.

Figure 469:

6. Create another load collector. a) For Name, enter Velocity.

b) For Card Image, select INVELB. c) Input the values as illustrated below.

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Figure 470:

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Dynamic.

3. Set Analysis type to Multibody dynamics. 4. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK. 5. Define INVEL. a) For INVEL, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select Velocity and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 471: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter slider_crank_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the slider_crank_complete.fem was written. The slider_crank_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present. Also, the following files will be output and which are specific to the random response analysis. slider_crank_complete_mbd.abf Binary plotting file. slider_crank_complete_mbd.h3d Binary results file (Modal results). slider_crank_complete_mbd.log Log file from OS-Motion containing the information on the joints and markers, simulation etc., which are specific to MBD analysis. slider_crank_complete_mbd.mrf Binary results file for plotting. slider_crank_complete_mbd.xml Model file in .xml format – solver intermediate input deck.

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Viewing the Results In this step you will view the results in HyperView, which will be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data. 1. From the OptiStruct panel of the Analysis page, click HyperView. The path and filename for slider_crank_complete.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data. The model and results are loaded in the current HyperView window. 2. Click the Contour panel toolbar icon

.

3. Under Results type: select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 472:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

Figure 473:

6. In the Contour panel, under Results type, select Element Stresses [2D & 3D].

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OptiStruct Tutorials Multibody Dynamics Analysis 7. Set Stress type to von Mises. 8. Click Apply. 9. Click the Start/Pause Animation icon to start the animation.

Figure 474:

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OS-T: 1920 Large Displacement Analysis of a Cantilever Beam In this tutorial, you will perform a multibody dynamics analysis (simulation type: Transient Analysis) of a slender cantilever beam using OptiStruct. Using HyperMesh, you will import an existing finite element model of a cantilever beam and setup the model (creation of joint, loading, and so on). You will use HyperView to post-process the large displacement results of the cantilever beam model.

Figure 475:

In this tutorial, you learn how to create a JOINT, a PFBODY, an MBMNTC and a multi-body dynamics subcase. The beam model consists of 10 different flexible bodies (PFBODY) and each body is to be connected through a fixed joint and rigid element (RBE2).

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Figure 476: Modeling RBE2

There are two RBE2's defined at the boundary of each body (one for each body at this boundary). The fixed joint will be created using coincident nodes which are independent nodes of each of the RBE2s.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the cantilever_beam_MBD.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The cantilever_beam_MBD.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Setting Up the Model Creating Joints In this step you will define all of the necessary joints required for this model. Only fixed joints for this model are needed. The fix joint at the left corner of body_1 will be created to represent clamped boundary condition. This fixed joint will be created using coincident nodes, so that coincident nodes need to be created first at the left corner of body_1. 1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. Create coincident nodes.

a) From menu bar, click Geometry > Create > Nodes > XYZ to open the Create Nodes panel. b) In the modeling window, on the upper left corner of body_1, click three times. The nodal coordinates (x=, y=, z=) of that node will be populated.

Figure 477: Location of Coincident Nodes

c) Click create. d) Create another coincident node on the lower left corner of body_1. e) Click return. 3. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 4. Create a fixed joint at the left corner of body_1. a) Set joint type to fixed. b) Select the coincident node in the upper, left corner as the first terminal and select the other coincident node at the same location as the second terminal. Tip: Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window. c) Click create.

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Figure 478: Fixed Joint

5. Create a fixed joint at the lower left corner of body_1. 6. Create a fixed joint at the boundary of each component. a) Set joint type to fixed. b) Zoom in to the boundary between Body_1 and Body_2. c) Select one of the coincident nodes as first terminal and select the other coincident nodes as second terminal. d) Click create.

Figure 479: Fixed Joint

7. Create a fixed joint for the boundary of each body. 8. Click return.

Creating PFBodies PFBODY is the Flexible Body Definition for Multibody Simulation. PFBODY defines a flexible body out of a list of finite element properties, elements, and grid points.

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You will have ten bodies apart from the ground body in your model. 1. From the Analysis page, click bodies. 2. Select the create subpanel. 3. In the body= field, enter pfbdy_1. 4. Click type= and select PFBODY.

5. Using the props selector, select body_1. 6. Click elems > bycollector, and select rigid_1. 7. Set number of modes to nmodes=, and enter 3. 8. Click create.

9. Select the parameters subpanel. 10. Set damping to dval=, and enter 10.0. 11. Click update.

12. Create a PFBODY for each flexible body. For body_2: define the following: • For body=, enter pfbdy_2.

• For props=, select body_2. • For elems=, select rigid_2. Make sure that all PFBODY have a damping of 10.0 defined in parameters subpanel. For pfbody_4, enter a value of 7 in the nmodes= field.

13. Click return.

Creating DTI, UNITS 1. From the menu bar, click Setup > Create > Control Cards to open the Control Cards panel. 2. Click DTI_UNITS. 3. Define the unit system, as shown in Figure 480.

Figure 480:

4. Click return twice to return to the main menu.

Creating MBSIM Load Collector The moment applied at the end of the beam, the gravity force that applies to the model and MBSIM bulk data card, which is to specify the parameter for multibody simulation, will be created in this step. 1. Create the mbmoment load collector.

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OptiStruct Tutorials Multibody Dynamics Analysis a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter mbmoment.

c) Set the Card Image to None. 2. Create the sim load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter sim.

c) Set the Card Image to MBSIM. d) Set TTYPE to END. e) For TIME, enter 0.5.

f) Set STYPE to DELTA. g) For DELTA, enter 2.0e-04. h) Set ITYPE to VSTIFF.

Creating an MBMNTC 1. Change the load type for moment to MBMNTC. a) From the Analysis page, select load types. b) Click moment= and select MBMNTC. c) Click return. MBMNTC is the moment based on the curve. 2. Create a curve. a) From the menu bar, click XYPlots > Curve Editor to open the Curve editor window. b) Click New. c) For name =, enter mycurve. d) Click proceed.

e) From the Curve List, select my curve. f) Populate the X Y table, as shown in Figure 481.

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Figure 481:

g) Click Update. h) Click Close. 3. In the Model Browser, Load Collectors folder, right-click on mbmoment and select Make Current from the context menu. 4. Create moments. a) From the Analysis page, click moments. b) Using the nodes selector, select the 2 nodes at right tip of a beam.

Figure 482: MBMNTC

c) Click the switch beside magnitude= and select curve, components. d) In the z comp= field, enter 1.0.

The x comp and y comp fields should remain at 0.

e) Click curve and select mycurve. f) Click create. g) Click return. 5. Click OptiStruct. This launches an OptiStruct run in a separate shell (DOS or Unix) which appears. If the optimization was successful, no error messages are reported to the shell. The optimization is complete when the message Processing complete appears in the shell.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor.

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2. For Name, enter Dynamic.

3. Set Analysis type to Multi-body dynamics. 4. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK. 5. Define MLOAD. a) For MLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select mbmoment and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 483: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cantilever_beam_MBD for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the cantilever_beam_MBD.fem was written. The cantilever_beam_MBD.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

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Viewing the Results In this step you will view the results in HyperView, which will be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data. 1. From the OptiStruct panel of the Analysis page, click HyperView. The path and filename for cantilever_beam_MBD.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data. The model and results are loaded in the current HyperView window. 2. Click the Contour panel toolbar icon

.

3. Under Results type: select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 484:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

Figure 485:

6. In the Contour panel, under Results type, select Element Stresses [2D & 3D].

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OptiStruct Tutorials Multibody Dynamics Analysis 7. Click Apply. 8. Click the Start/Pause Animation icon to start the animation.

Figure 486:

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OS-T: 1930 Generating Flexible Body for use in MotionSolve In this tutorial you will use an existing finite element model to generate a flexible body for use in MotionSolve. You will run the model in OptiStruct.

Figure 487:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the susp_sla.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The susp_sla.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Setting Up the Model Creating Load Collectors to Conduct the Flexible Body Reduction In this step, two collectors will be created; one for the ASET that defines the connecting degrees of freedom of the flexible body and the other for the method and parameters for the component mode synthesis. 1. Create the ASET load collector. This load collector will be used to define connecting degrees of freedom of the flexible body to the multi-body system. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter ASET.

c) Click Color and select a color from the color palette. d) Set Card Image to None. 2. Create the CMS load collector. This load collector will be used to define the component mode synthesis method and parameters. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter CMS.

c) Click Color and select a color from the color palette. d) Set Card Image to CMSMETH. e) Leave METHOD set to the default value, which is CB (Craig-Bampton). f) For NMODES (number of modes), enter 10.

Modifying Load Types 1. From the Analysis page, click the load types panel. 2. Click constraint = > ASET. 3. Click return.

Creating the ASETs 1. In the Model Browser, Load Collectors folder, right-click ASET and select Make Current from the context menu. 2. From the menu bar, select BCs > Create > Constraints to open the Constraints panel. 3. Create the first constraint. a) Select the following degrees of freedom: dof1, dof2, and dof3.

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Tip: Deselect degrees of freedom by right-clicking on a checked (selected) box.

Figure 488:

b) Using the nodes selector, select the nodes that sit in the middle of the multi-node rigid on the primary attachment point of the control arm to the chassis. c) Click create. 4. Create the second constraint. a) Select the degrees of freedom, dof2 and dof3. b) Using the nodes selector, select the node and the last attachment point of the control arm.. c) Click create. 5. Create the third constraint. a) Select the degree of freedom, dof3. b) Using the nodes selector, select the top node in the rigid which would fasten the bottom of the shock assembly to the control arm. c) Click create. 6. Create the fourth constraint. a) Select the degrees of freedom, dof1, dof2, and dof3. b) Using the nodes selector, select the top node in the rigid on the boss to the right. c) Click create.

Figure 489: Constraints Applied to the Control Arm Model

Creating Subcase

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1. From the , click Setup > Create > Control Cards to open the Control Cards panel. 2. Click GLOBAL_CASE_CONTROL. 3. Enable CMSMETH. 4. Click CMSMETH and select the CMS load collector. 5. Click return to return to the Control Cards panel.

Defining Output Request 1. From the menu bar, click Setup > Create > Control Cards to open the Control Cards panel. 2. Define the units system for the flex body output. The units should be defined consistent with the material properties of the material defined for this model. This way, you will not need to take care of the units of Multi-body Dynamics Analysis. a) Click DTI_UNITS. Tip: To check the material properties of your model, go to the Model Browser, Materials folder and click MAT1_1. In the Entity Editor, view the Elastic modulus (2.1e+05), Poisson's Ratio (0.3) and the Density of the material (7.9e-09). For this model, the material used is Steel. Since the values of the material properties provided are consistent with Megagram, Newton, Millimeter, Second, the MGG N MM S sequence is selected for this control card. b) The values of the material properties provided are consistent with Megagram, Newton, Millimeter, Second, therefore select the MGG N MM S sequence. c) Click return. 3. Define the analysis type. a) Click GLOBAL_OUTPUT_REQUEST. b) Select STRESS. c) Select the options shown below.

Figure 490:

d) Click return. 4. Create the output control for the component mode synthesis. a) Click OUTPUT. b) Select the options shown below.

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Figure 491:

c) Click return. 5. Create a title. a) Click TITLE. b) Enter a title for the analysis. c) Click return twice.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 492: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter susp_sla for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all.

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6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the susp_sla.fem was written. The susp_sla.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: susp_sla.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. susp_sla.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. susp_sla.h3d HyperView binary results file. susp_sla.res HyperMesh binary results file. susp_sla.stat Summary, providing CPU information for each step during analysis process.

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OS-T: 1940 MBD Rigid Contact In this tutorial you will how to create model contacts using HyperMesh. Contact constraints are very common in the mechanisms/general machinery domain. MotionSolve uses the penalty-based Poisson contact force model for calculating the magnitude and direction of the contact and friction forces. The Curved Pentagon Positive Return Cam system is used to define the contacts. In this system the curved pentagon rolls inside the circle and translates the slider.

Figure 493: Rigid Body Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the for_contact_tutorial.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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3. Click Open. The for_contact_tutorial.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Rigid Bodies (PRBODY) PRBODY is the Rigid Body Definition for Multi-body Simulation. PRBODY defines a rigid body out of a list of finite element properties, elements and grid points. There will be five bodies apart from the ground body in our model via: the stand, the slider, the driver, the pentagon and the circle. Pre-defined free nodes will be used to define the bodies and joints. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter stand.

4. Click type= and select PRBODY. 5. Using the props selector, select Stand1. 6. Double-click nodes and select by id, then enter 2, 19391, and 19402. 7. Click create.

8. Define PRBODY for the remaining components. body=

type=

props

free nodes

Slider

PRBODY

Slider2

4, 19399

Driver

PRBODY

Driver3

19392, 19395

Pentagon

PRBODY

Pentagon4

4246, 19396

Circle

PRBODY

Circle5

414, 19400

Ground

GROUND

Not required

19401

9. Click return.

Creating Joints In this step you will create all of joints needed for the model. The first joint is the fixed joint between the stand and ground body. The second joint is a revolute joint between the stand and driver, the third joint is the translational joint that connects the slider to the stand, the fourth joint is the revolute joint

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between the driver and the pentagon, and the fifth joint is the fixed joint between the slider and the circle. DOF = 5*6 - (5+5+6+6+5+1) = 2 Removes translational dof

Type of Joint

Removes rotational dof

Removes total number of dof

Revolute

3

2

5

Fixed

3

3

6

Translational

2

3

5

Motion (rev)

3

2

1

Figure 494: Joint Locations in the Model

1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 3. Create a fixed joint between the stand and ground. a) Set joint type to fixed. b) Select node ID 19401 as the first terminal and node ID 19402 as the second terminal.

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Tip: The first and second terminals are corresponding to the bodies that are connected by the joint. Nodes 19401 and 19402 are coincident. Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window. c) Click create. 4. Create a fixed joint between the slider and the circle. a) Set joint type to fixed. b) Select node ID 19399 as the first terminal and node ID 19400 as the second terminal. c) Click create. 5. Create a revolute joint between the stand and driver. a) Set joint type to revolute. b) Select node ID 19391 as the first terminal and node ID 19392 as the second terminal. c) Set the first orientation selector to vector, then select y-axis. d) Click create. 6. Create a revolute joint between the driver and pentagon body. a) Set joint type to revolute. b) Select node ID 19395 as the first terminal and node ID 19396 as the second terminal. c) Set the first orientation selector to vector, then select y-axis. d) Click create. 7. Create a translational joint between the slider and stand. a) Set joint type to translational. b) Select node ID 2 as the first terminal and node ID 4 as the second terminal. c) Set the first orientation selector to vector, then select x-axis. d) Click create. 8. Click return to exit the panel.

Defining a Contact In this step you will use pre-defined element sets to add a contact to the model. The element sets are defined from the Analysis page, entity sets by choosing a set of elements. The set of elements on the face of the pentagon body is named master and the sets elements on the face of the circle body is named slave. 1. Create a contact. a) From the Analysis page, click the interfaces panel. b) Select the create subpanel. c) In the name= field, enter Contact. d) Click type= and select MBCNTR. e) Click create.

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Figure 495:

2. Add pre-defined element sets to the contact. a) Select the add subpanel. b) Set master to sets, then use the sets selector to select mas. c) Set slave to sets, then use the sets selector to select Sla. d) Click update.

Figure 496: Interfaces Panel - Contact

3. Edit the contact's card image. a) Select the card image subpanel. b) Click edit. c) In the Card Image dialog, set CNFTYPE to POISSON. d) Enter the values as shown in the image below.

Figure 497:

e) Click return. 4. Click return to exit the Interface panel.

Defining the Motion Constraint In this step you will create the motion which drives the mechanism. 1. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 2. Double-click nodes and select by id, then enter node id 19392.

3. Uncheck all degrees of freedom; except for dof5. In the dof= field, enter 1.

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Figure 498: Constraints Panel - Motion

4. Click load types = and select MOTNG(V). 5. Click create to create the constraint. 6. Click return to go to the Analysis page. A new load collector (auto1) has been added to the model. The motion is assigned to this load collector and will be used as reference in the OptiStruct subcase.

Creating Load Collectors In this step you will create the gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multibody simulation. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter gravity.

3. Click Color and select a color from the color palette. 4. Set Card Image to GRAV. 5. Input the values as illustrated below.

Figure 499:

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OptiStruct Tutorials Multibody Dynamics Analysis 6. Create another load collector. a) For Name, enter SIM.

b) For Card Image, select MBSIM. c) Input the values as illustrated below.

Figure 500:

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Dynamic.

3. Set Analysis type to Multi-body dynamics. 4. Define MLOAD. a) For MLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select gravity and click OK. 5. Define MBSIM.

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a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK. 6. Define MOTION. a) For MOTION, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select auto1 and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 501: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter for_contact_tutorial for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the for_contact_tutorial.fem was written. The for_contact_tutorial.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: for_contact_tutorial.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results.

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for_contact_tutorial.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. for_contact_tutorial.h3d HyperView binary results file. for_contact_tutorial.res HyperMesh binary results file. for_contact_tutorial.stat Summary, providing CPU information for each step during analysis process. There are a few more files written to the directory with the name for_contact_tutorial_mbd.

Viewing the Results In this step you will view the results in HyperView, which will be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data. 1. From the OptiStruct panel of the Analysis page, click HyperView. The path and filename for for_contact_tutorial.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data. The model and results are loaded in the current HyperView window. 2. Click the Contour panel toolbar icon

.

3. Under Results type: select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 502:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

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OS-T: 1950 Curve to Curve Constraint In this tutorial, you learn how to model a CVCV (curve-to-curve) joint using HyperMesh A CVCV (curve-to-curve) joint is a higher pair constraint. The constraint consists of a planar curve on one body rolling and sliding on a planar curve on a second body. The curves are required to be coplanar. This constraint can act as a substitute to contact modeling in many cases where the contact occurs in a plane. One such case is the Curved Pentagon Positive Return Cam system in which the curved pentagon rolls inside the circle and translates the slider. Instead of modeling the contact between the pentagon and the circle, a CVCV constraint between their profiles will be specified.

Figure 503: Rigid Body Model

In this tutorial, a Curved Pentagon Positive Return Cam system is modeled with the help of a CVCV constraint.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the for_cvcv_tutorial.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The for_cvcv_tutorial.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Rigid Bodies (PRBODY) PRBODY is the Rigid Body Definition for Multi-body Simulation. PRBODY defines a rigid body out of a list of finite element properties, elements and grid points. There will be five bodies apart from the ground body in our model via: the stand, the slider, the driver, the pentagon and the circle. Pre-defined free nodes will be used to define the bodies and joints. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter stand.

4. Click type= and select PRBODY. 5. Using the props selector, select Stand1. 6. Double-click nodes and select by id, then enter 2, 19392, and 19402. 7. Click create.

8. Define PRBODY for the remaining components. body=

type=

props

free nodes

Slider

PRBODY

Slider2

4, 19398, 19400

Driver

PRBODY

Driver3

19391, 19395

Pentagon

PRBODY

Pentagon4

19396

Circle

PRBODY

Circle5

19397, 19399

Ground

GROUND

Not required

19401

9. Click return.

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Creating Joints In this step you will create all of joints needed for the model. The first joint is the fixed joint between the stand and ground body. The second joint is a revolute joint between the stand and driver, the third joint is the translational joint that connects the slider to the stand, the fourth joint is the revolute joint between the driver and the pentagon, and the fifth joint is the fixed joint between the slider and the circle. You will also create a CVCV joint. DOF = 5*6 - (5+5+6+6+5+1) = 2 Removes translational dof

Type of Joint

Removes rotational dof

Removes total number of dof

Revolute

3

2

5

Fixed

3

3

6

Translational

2

3

5

Motion (rev)

3

2

1

Figure 504: Joint Locations in the Model

1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 3. Create a fixed joint between the stand and ground. a) Set joint type to fixed.

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b) Select node ID 19401 as the first terminal and node ID 19402 as the second terminal. Tip: The first and second terminals are corresponding to the bodies that are connected by the joint. Nodes 19401 and 19402 are coincident. Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window. c) Click create. 4. Create a fixed joint between the slider and the circle. a) Set joint type to fixed. b) Select node ID 19399 as the first terminal and node ID 19400 as the second terminal. c) Click create. 5. Create a revolute joint between the stand and driver. a) Set joint type to revolute. b) Select node ID 19391 as the first terminal and node ID 19392 as the second terminal. c) Set the first orientation selector to vector, then select y-axis. d) Click create. 6. Create a revolute joint between the driver and pentagon body. a) Set joint type to revolute. b) Select node ID 19395 as the first terminal and node ID 19396 as the second terminal. c) Set the first orientation selector to vector, then select y-axis. d) Click create. 7. Create a translational joint between the slider and stand. a) Set joint type to translational. b) Select node ID 2 as the first terminal and node ID 4 as the second terminal. c) Set the first orientation selector to vector, then select x-axis. d) Click create. 8. Create a CVCV joint. Pre-defined curves will be used in order to add a CVCV joint. These curves are defined from the Analysis page, entity sets by choosing a set of nodes. The curve on the pentagon body is named master and the curve on the circle body is named slave. a) Set joint type to cvcv. b) Select 4246 as the first terminal and 414 as the second terminal. c) For the first curve, click set= and select master. d) For second curve, click set= and select slave. e) Click create. 9. Click return to exit the panel.

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Defining the Motion Constraint In this step you will create the motion which drives the mechanism. 1. From the menu bar, click BCs > Create > Constraints to open the Constraints panel. 2. Double-click nodes and select by id, then enter node id 19392.

3. Uncheck all degrees of freedom; except for dof5. In the dof= field, enter 1.

Figure 505: Constraints Panel - Motion

4. Click load types = and select MOTNG(V). 5. Click create to create the constraint. 6. Click return to go to the Analysis page. A new load collector (auto1) has been added to the model. The motion is assigned to this load collector and will be used as reference in the OptiStruct subcase.

Creating Load Collectors In this step you will create the gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multibody simulation. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter gravity.

3. Click Color and select a color from the color palette. 4. Set Card Image to GRAV. 5. Input the values as illustrated below.

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Figure 506:

6. Create another load collector. a) For Name, enter SIM.

b) For Card Image, select MBSIM. c) Input the values as illustrated below.

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OptiStruct Tutorials Multibody Dynamics Analysis

Figure 507:

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Dynamic.

3. Set Analysis type to Multi-body dynamics. 4. Define MLOAD. a) For MLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select gravity and click OK. 5. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK.

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6. Define MOTION. a) For MOTION, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select auto1 and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 508: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter for_cvcv_tutorial for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the for_cvcv_tutorial.fem was written. The for_cvcv_tutorial.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: for_cvcv_tutorial.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. for_cvcv_tutorial.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run,

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information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. for_cvcv_tutorial.h3d HyperView binary results file. for_cvcv_tutorial.res HyperMesh binary results file. for_cvcv_tutorial.stat Summary, providing CPU information for each step during analysis process.

Viewing the Results In this step you will view the results in HyperView, which will be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data. 1. From the OptiStruct panel of the Analysis page, click HyperView. The path and filename for for_cvcv_tutorial.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data. The model and results are loaded in the current HyperView window. 2. Click the Contour panel toolbar icon

.

3. Under Results type: select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 509:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

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OS-T: 1960 Defining Point to Deformable Curve Joint In this tutorial, a multibody dynamics analysis (simulation type: Transient Analysis) of a hook on a flexible cable are performed using OptiStruct. An existing finite element model is imported into HyperMesh. The rest of the setup (creation of joint, loading, etc.) is done in HyperMesh. HyperView is used to post-process the large deformations of the flexible cable model.

Figure 510: Hook Rolling on a Cable

You will learn how to create JOINTS (Fixed, PTDCV), a PFBODY, a PRBODY, a MBDCRV, and a multi-body dynamics subcase.

Figure 511: Model in HyperMesh

The flexible cable consists of 50 different CBAR elements (PFBODY) and the end of this flexible body is connected to ground (GROUND) using fixed joints.

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The Hook (PRBODY) is an external graphic and is connected to the flexible cable by the PTDCV joint.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the flex_cable.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The flex_cable.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Rigid Bodies (PRBODY) 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter Hook.

4. Click type= and select PRBODY. 5. Using the props selector, select Hook. 6. Double-click nodes and select by id, then enter 14399. 7. Click create.

8. Click return.

Creating Flex Bodies (PFBODY) PFBODY is the Flexible Body Definition for Multibody Simulation. PFBODY defines a flexible body out of a list of finite element properties, elements, and grid points.

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OptiStruct Tutorials Multibody Dynamics Analysis 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter Cable.

4. Click type= and select PFBODY. 5. Using the props selector, select Cable. 6. Double-click nodes and select by id, then enter 1, 2. 7. Set CMS Method to Craig-Bampton.

8. Verify frequency upper bound is set to upper bound default. 9. Toggle number of modes to nmodes=, and enter 15.

Figure 512:

10. Click create. 11. Click return.

Creating GROUND Bodies (GROUND) Note: The selection of a property is not required when defining a ground body. 1. From the Analysis page, click the bodies panel. 2. Select the create subpanel. 3. In the body= field, enter Ground.

4. Click type= and select GROUND. 5. Double-click nodes and select by id, then enter 14397, 14398. 6. Click create.

Defining the Deformable Curve 1. In the Model Browser, right-click and select Create > Set. A default set template displays in the Entity Editor. 2. For Name, enter deform_curve. 3. Set Card Image to MBDCRV.

4. Verify Set Type is set to ordered. 5. Select entity IDs.

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a) For Entity IDs, click 0 Nodes > Nodes. b) In the panel area, click node list > by path. c) Select the nodes at two ends of the flexible cable made up by CBAR elements. All of the nodes are automatically selected on the cable. d) Click proceed.

Figure 513:

Creating Joints You will create all the necessary joints including the PTDCV joint. Three joints for the model are needed. Two fixed joints between the Cable ends to the Ground, and one PTDCRV between the Hook and the Cable. 1. Create the component, joints. a) In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. b) For Name, enter joints.

2. From the menu bar, click Mesh > Create > 1D Elements > Joints. The Joints panel opens. 3. Create a fixed joint between one end of the Cable and Ground. a) Set joint type to fixed. b) Select node ID 1 as first terminal and select node ID 14397 as second terminal. Tip: Nodes 1 and 14397 are coincident. Use coincident node picking in the options panel > graphics subpanel to help you select these coincident nodes in the modeling window.

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c) Click create. 4. Create the fixed joint between the other end of the Cable and Ground. a) Set joint type to fixed. b) Select node ID 2 as first terminal and select node ID 14398 as second terminal. c) Click create. 5. Create the PTDCV joint. a) Set joint type to ptdcv. b) Select node ID 14399 as first terminal. c) Click set= and select deform_curve. The deform_curve entity set is defined as MBDCRV. d) Click create.

Figure 514:

6. Click return.

Creating Load Collectors In this step you will create the gravity force that applies to the model and MBSIM Bulk Data card, which is to specify the parameter for multibody simulation. 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter gravity.

3. Click Color and select a color from the color palette. 4. Set Card Image to GRAV. 5. Input the values as illustrated below.

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Figure 515:

6. Create another load collector. a) For Name, enter SIM.

b) For Card Image, select MBSIM. c) Input the values as illustrated below.

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OptiStruct Tutorials Multibody Dynamics Analysis

Figure 516:

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Dynamic.

3. Set Analysis type to Multi-body dynamics. 4. Define MLOAD. a) For MLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select gravity and click OK. 5. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SIM and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 517: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter flex_cable for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the flex_cable.fem was written. The flex_cable.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: flex_cable.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. flex_cable.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. flex_cable.h3d HyperView binary results file. flex_cable.res HyperMesh binary results file. flex_cable.stat Summary, providing CPU information for each step during analysis process.

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Viewing the Results In this step you will view the results in HyperView, which will be launched from within the OptiStruct panel of HyperMesh. HyperView is a complete post-processing and visualization environment for finite element analysis (FEA), multibody system simulation, video and engineering data. 1. From the OptiStruct panel of the Analysis page, click HyperView. The path and filename for flex_cable.h3d appears in the fields to the right of Load model and Load results. This is fine because the .h3d format contains both model and results data. The model and results are loaded in the current HyperView window. 2. Click the Contour panel toolbar icon

.

3. Under Results type: select Displacement(v). 4. Click Apply. 5. Start/stop the animation using the Animation Controls in the panel next to the playback controls.

Figure 518:

a) Verify Animate Mode is set to

(Transient).

b) Click the Start/Pause Animation icon to start the animation. c) With the animation running, use the bottom slider bar to adjust the speed of the animation. d) Click the Start/Pause Animation icon again to stop the animation.

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Topology Optimization Topology Optimization

This chapter covers the following: •

OS-T: 2000 Design Concept for a Structural C-Clip (p. 529)

•

OS-T: 2005 Design Concept for a Structural C-Clip with Minimum Member Size Control (p. 545)

•

OS-T: 2010 Design Concept for an Automotive Control Arm (p. 549)

•

OS-T: 2020 Increasing Natural Frequencies of an Automotive Splash Shield with Ribs (p. 563)

•

OS-T: 2030 Control Arm with Draw Direction Constraints (p. 577)

•

OS-T: 2040 Spot Weld Reduction using CWELD and 1D (p. 585)

•

OS-T: 2050 Pattern Repetition (p. 589)

•

OS-T: 2060 Symmetry and Draw Direction Constraints Applied Simultaneously (p. 598)

•

OS-T: 2070 Reduced Model using DMIG (p. 605)

•

OS-T: 2080 Hook with Stress Constraints (p. 618)

•

OS-T: 2090 Extrusion Constraints (p. 625)

•

OS-T: 2095 Frequency Response Optimization of a Rectangular Plate (p. 631)

•

OS-T: 2098 Excavator Arm (p. 651)

9

OptiStruct Tutorials Topology Optimization

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OS-T: 2000 Design Concept for a Structural C-Clip In this tutorial you will perform a topology optimization on a model to create a new topology for the structure, removing any unnecessary material. The resulting structure is lighter and satisfies all design constraints. The topology optimization technique yields a new design and optimal material distribution. Topology optimization allows designers to start with a design that already has the advantage of optimal material distribution and is ready for design fine tuning with shape or size optimization. The optimization problem for this tutorial is stated as: Objective

Minimize volume fraction.

Constraints

Translation in the y-axis for node A < 0.07mm. Translation in the y-axis at node B > -0.07mm.

Design variables

The density of each element in the design space.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the cclip.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The cclip.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model

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Creating the Material 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter steel.

3. Set Card Image to MAT1. 4. Enter the material values next to the corresponding fields. a) For E (Young's Modulus), enter 2.1E5. b) For NU, (Poisson's Ratio), enter 0.3. c) For RHO (Mass Density),

A new material, steel, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Creating the Property 1. In the Model Browser, right-click and select Create > Property from the context menu. A default property displays in the Entity Editor. 2. For Name, enter prop_shell. 3. Set Card Image to PSHELL.

4. Enter the property values next to the corresponding fields. An empty Value field indicates that it is turned off. To edit these properties, click on the blank Value fields next to them and enter the required values. a) For Material, click Unspecified > Material. In the Select Material dialog, select steel and click OK. b) For T (thickness of the plate), enter 1.0. A new property, prop_shell, has been created as a 2D PSHELL. Material information is also linked to this property.

Assigning a Material and Property to the comp_shell Component 1. In the Model Browser, Components folder, click comp_shell. The component displays in the Entity Editor. 2. For Property, click Unspecified > Property. In the Select Property dialog, select prop_shell and click OK.

Applying Loads and Boundary Conditions

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Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter constraints.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. 5. Create another load collector. a) For Name, enter forces.

b) For Card Image, select None.

Creating Constraints In this step you will create SPC constraints and assign them to the Constraints load collector. 1. From the Model Browser, Load Collectors folder, right-click on Constraints and select Make Current from the context menu. 2. From the Analysis page, click constraints. 3. Create the first constraint. a) Using the nodes selector, select the node indicated in Figure 519. b) Select the degree of freedom, dof3; unselect all others. c) Click create.

Figure 519:

4. Create the second constraint. a) Using the nodes selector, select the node indicated in Figure 520. b) Select the degrees of freedom, dof1 - dof3; unselect all others. c) Click create.

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Figure 520:

5. Create the third constraint. a) Using the nodes selector, select the node indicated in Figure 521. b) Select the degree of freedom, dof2; unselect all others. c) Click create.

Figure 521:

6. Click return.

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Creating Forces In this step, you will load the structure with two opposing forces of 100.0 N at the opposite tips of the opening of the c-clip. 1. From the Model Browser, Load Collectors folder, right-click on Forces and select Make Current from the context menu. 2. From the Analysis page, click forces. 3. Create a force at the top of the opening of the c-clip. a) Using the nodes selector, select the node at the top of the opening of the clip. b) In the magnitude= field, enter 100. c) Set the vector selector to y-axis. d) Click create.

Figure 522:

4. Create a force at the bottom of the opening of the c-clip. a) Using the nodes selector, select the node at the bottom of the opening of the clip. b) In the magnitude= field, enter -100. c) Set the vector selector to y-axis. d) Click create.

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Figure 523:

5. To provide a separation between the arrows, enter 7 in the uniform size= field.

Figure 524:

6. Click return to go back to the Analysis page.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter opposing forces. 3. Set Analysis type to linear static. 4. Define SPC. a) For SPC, click Unspecified > Loadcol.

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b) In the Select Loadcol dialog, select constraints and click OK. 5. Define LOAD. a) For LOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select forces and click OK.

Submitting the Job A linear static analysis of this C-clip is performed prior to the definition of the optimization process. An analysis identifies the responses of the structure before optimization to ensure that constraints defined for the optimization are reasonable. 1. From the Analysis page, click the OptiStruct panel.

Figure 525: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cclip_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Clear the options field. 9. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the cclip_complete.fem was written. The cclip_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results

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1. From the OptiStruct panel, click HyperView. HyperView launches the cclip.mvw file which loads the model and the results files. 2. On the Results toolbar, click

to open the Contour panel.

3. Under Result type, select Displacement(v) and Y. 4. Click Apply.

Figure 526: Contour of Y Displacements

5. Verify if the values are equivalent to those in Figure 526. 6. From the Page Control toolbar, click the page delete icon to delete the HyperView page.

Figure 527:

HyperView closes. 7. Click return to exit the panel.

Setting Up the Optimization The finite element model, consisting of shell elements, element properties, material properties, and loads and boundary conditions has been defined. Now a topology optimization will be performed with the goal of minimizing the amount of material to be used. Typically, removing the material in an existing volume with the same loads and boundary conditions makes the model less stiff and more prone to deformation. Therefore, you need to track the displacements (which represent the stiffness of the structure) and constrain the optimization process such that the least material necessary is used and overall stiffness is also achieved.

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The forces in the structure are applied on the outer nodes of the opening of the clip, making those two nodes critical locations in the mesh where the maximum displacement is likely to occur. In this tutorial, you will apply a displacement constraint on the nodes so that they would not displace more than 0.07 in the y-axis.

Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter d_shell. 5. Set type: to PSHELL.

6. Using the props selector, select prop_shell. 7. Verify that the base thickness is 0.0. A value of 0.0 implies that the thickness at a specific element can go to zero, and therefore becomes a void. 8. Click create. 9. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter upperdis.

b) Below response type, select static displacement. c) Set the displacement type to dof2. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

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d) Click create.

Figure 528:

5. Create another displacement response, named lowerdis. Using the nodes selector, select the node labeled B, on the lower opening of the c-clip.

Figure 529:

6. Click return to go back to the Optimization panel.

Creating Constraints on Displacement Responses In this step, the upper and lower bound constraint criteria for this analysis will be set. 1. Click the Dconstraints panel. 2. Create the upper bound constraint. a) In the constraint= field, enter c_upper.

b) Check the box next to upper bound, then enter 0.07. c) Click response= and select upperdis.

d) Using the loadsteps selector, select opposing forces. e) Click create.

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3. Create the lower bound constraint. a) In the constraint= field, enter c_lower.

b) Check the box next to lower bound, then enter -0.07. c) Click response= and select lowerdis.

d) Using the loadsteps selector, select opposing forces. e) Click create. 4. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select volfrac. 4. Click create. 5. Click return twice to exit the Optimization panel.

Creating the SCREEN Card The SCREEN control card enables OptiStruct to output the optimization iterations to the output window. 1. From the Analysis page, click control cards. 2. In the Card Image dialog, click SCREEN. 3. Click return. 4. Click return.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cclip_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED.

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FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file cclip_complete.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: cclip_complete.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. cclip_complete.HM.comp.tcl HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. cclip_complete.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. cclip_complete.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the cclip_complete.fem file. cclip_complete.res HyperMesh binary results file. cclip_complete.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. cclip_complete.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. cclip_complete_hist.mvw Contains the iteration history of the objective, constraints, and the design variables. It can be used to plot curves in HyperGraph, HyperView, and MotionView. cclip_complete.h3d HyperView binary results file.

Viewing the Results Element density results are output to the cclip_complete_des.h3d file from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iterations by default into cclip_complete_s#.h3d files, where # specifies the sub case ID.

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Viewing an Iso Value Plot of Element Densities An Iso Value plot provides information about element densities. Iso Value retains all of the elements at and above a certain density threshold. You should pick a density threshold that provides the structure that suits your needs. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and opens the session file cclip_complete.mvw which contains two pages with the results from two files. Page 2

Displays the file cclip_complete_des.h3d, which contains the Optimization history results (element density).

Page 3

Displays the cclip_complete_s1.h3d, which contains the Subcase 1 results; initial and final (displacement stress).

2. Verify that you are on page 2. 3. In the Results Browser, under the load case section, select Design and the last iteration listed to review the optimized iteration result.

Figure 530:

4. On the Standard Views toolbar, click XY Top Plane View to set the correct view. 5. From the menu bar, click Results > Plot > Iso. 6. In the panel area, set Result type to Element Densities. 7. Click Apply. 8. In the Current value field, enter 0.3.

9. Under Current value, move the slider to change the density threshold. Use this tool to get a better look at the material layout and the load paths from OptiStruct. The iso value in the modeling window update interactively when you scroll to a new value.

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Figure 531: Iso Value Plot of Element Densities

Comparing Original Static Contour to Optimized Material Layout 1. In HyperView, click

to go to page 3.

The cclip_complete_s1.h3d file displays, which contains the static subcase results for the first and last iteration steps. 2. On the Page Controls toolbar, from the Page Window Layout drop-down, click page into two vertical windows. 3. On the Standard Views toolbar, click XY Top Plane View to set the correct view. 4. From the menu bar, click Results > Plot > Contour. 5. Under Result type, select Displacement and Y. 6. Click Apply. 7. Click

to open the Deformed panel.

8. Under Deformed shape, enter 100 in the Value field. 9. Under Undeformed shape, set Show to Edges. 10. Click Apply. 11. Copy the contents of the first window to the second window. a) From the menu bar, click Edit > Copy > Window. b) Click the empty window. c) From the menu bar, click Edit > Paste > Window.

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12. Switch the animation mode to Linear

.

13. With the second window selected, select Iteration 28.

Figure 532:

14. Create a third page. a) From the menu bar, click Edit > Copy > Page. b) From the menu bar, click Edit > Paste > Page. 15. Activate the first window and click

to open the Contour panel.

16. Under Result type, select Element Stresses (2D & 3D) (t). 17. Set Averaging method to Simple. 18. Click Apply. 19. In the first window, right-click and select Apply Style > Current Page > Contour from the context menu.

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Figure 533:

Only use these stress results as a reference to help you understand how far from the limits the design is. Remember that topologic optimization will show you a concept shape. The stress results should be validated during the next design phases.

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OS-T: 2005 Design Concept for a Structural C-Clip with Minimum Member Size Control In this tutorial you will setup a topology optimization problem that applies the technique of minimum member size control on the elements of the model to achieve a discrete solution. Performing topology optimizations early in the conceptual design stage results in the generation of a good baseline design and contributes to a shorter design cycle. One challenge with post-processing topology optimization results is that the results may have several intermediate density elements or checkerboard patterns which can be interpreted either as solid members or as a void. If these semidense elements are interpreted as thin members, the final design is harder to manufacture. OptiStruct offers the minimum member size control method which provides some control over member size in the final topology designs by defining the least dimension required in the final design. It helps achieve a discrete solution by eliminating the intermediate density elements and checkerboard density pattern, resulting in a discrete and better-reinforced structure, which is easier to interpret and also easier to manufacture.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the cclip_complete.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

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Applying Minimum Member Size Control Parameter Minimum member size control will be applied to achieve a discrete solution. 1. Click inside the modeling window, then press F4. The Distance panel opens. 2. Select the two nodes subpanel. 3. Measure the distance between nodes on an element. a) Using the N1 selector, select any node. b) Using the N2 selector, select another node on the same element. 4. Measure the distance between nodes on other elements to obtain the average element size. The average element size for this model is about 2.5. Note: It is recommended that the MINDIM value be three times larger than this average element size unless the element's mesh is aligned; in which case it can be two times larger. 5. Click return to go back to the Analysis page. 6. From the Analysis page, click optimization. 7. Click topology. 8. Select the parameters subpanel. 9. Click review. 10. Click desvar= and select shells. 11. Click the toggle next to minmemb off and select mindim=, then 5.

12. Click update. A minimum member size control has been applied on this topology optimization problem. 13. Click return twice to go back to Analysis page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cclip_complete_min_member for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization.

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9. Click Close. The result files load automatically into HyperMesh and HyperView on completion of the run, so you can proceed directly to the post-processing step.

Viewing an Iso Value Plot of Element Densities An Iso Value plot provides information about element densities. Iso Value retains all of the elements at and above a certain density threshold. You should pick a density threshold that provides the structure that suits your needs. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and opens the session file cclip_complete_min_member.mvw which contains two pages with the results from two files. Page 2

Displays the file cclip_complete_min_member_des.h3d, which contains the Optimization history results (element density).

Page 3

Displays the cclip_complete_min_member_s1.h3d, which contains the Subcase 1 results; initial and final (displacement stress).

2. Verify that you are on page 2. 3. In the Results Browser, under the load case section, select Design and the last iteration listed to review the optimized iteration result.

Figure 534:

4. On the Standard Views toolbar, click XY Top Plane View to set the correct view. 5. From the menu bar, click Results > Plot > Iso. 6. In the panel area, set Result type to Element Densities. 7. Click Apply. 8. In the Current value field, enter 0.3.

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9. Compare the results to the one you achieved in the previous optimization without the application of minimum member size control, OS-T: 2000 Design Concept for a Structural C-Clip. The iso value plot displayed is similar to the one previously achieved. The smaller members in the original iso surface plot are replaced by a more discrete rib pattern. This design is easier to manufacture.

Figure 535: Iso Value Plot of Element Densities

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OS-T: 2010 Design Concept for an Automotive Control Arm In this tutorial you will use OptiStruct's topology optimization functionality to create a design concept for an automotive control arm required to meet performance specifications. The finite element mesh contains designable and non-designable regions. Part specifications constrain the resultant displacement of the point where loading is applied for three load cases to 0.05mm, 0.02mm, and 0.04mm, respectively. The optimal design would use as little material as possible.

Figure 536: Finite Element Mesh Containing Designable (blue) and Non-Designable (yellow) Material

A finite element model representing the designable and non-designable material is imported into HyperMesh. Appropriate properties, boundary conditions, loads, and optimization parameters are defined and the OptiStruct software determines the optimal material distribution. The results (the material layout) are viewed as contours of a normalized density value ranging from 0.0 to 1.0 in the design space. Iso surfaces are also used to view the density results. Areas that need reinforcement will tend towards a density of 1.0. The optimization problem for this tutorial is stated as: Objective

Minimize volume.

Constraints

SUBCASE 1. Resultant displacement of the point where loading is applied must be less than 0.05mm. SUBCASE 2. Resultant displacement of the point where loading is applied must be less than 0.02mm. SUBCASE 3. Resultant displacement of the point where loading is applied must be less than 0.04mm.

Design Variables

Element density (and corresponding stiffness of the element) of each element in the design space.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the carm.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The carm.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating the Material 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter Steel.

3. Set Card Image to MAT1. 4. Enter the material values next to the corresponding fields. a) For E (Young's Modulus), enter 2.0E5. b) For NU, (Poisson's Ratio), enter 0.3. c) For RHO (Mass Density),

A new material, Steel, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Creating the Property 1. In the Model Browser, right-click and select Create > Property from the context menu. A default property displays in the Entity Editor.

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2. For Name, enter nondesign_prop. 3. Set the Card Image to PSOLID.

4. Assign a material to the property. a) For Material, click Unspecified > Material. b) In the Select Material dialog, select Steel and click OK.

Assigning a Material and Property to the nondesign Component 1. In the Model Browser, Components folder, click nondesign. The component displays in the Entity Editor. 2. For Property, click Unspecified > Property. In the Select Property dialog, select nondesign_prop and click OK. 3. Repeat the above steps to assign the design_prop property to the design component.

Applying Loads and Boundary Conditions Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter SPC.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. 5. Repeat the above steps to create load collectors named Brake, Corner, and Pothole.

Applying Constraints In this step you will create SPC constraints and assign them to the SPC load collector. 1. From the Model Browser, Load Collectors folder, right-click on SPC and select Make Current from the context menu. 2. From the Analysis page, click constraints. 3. Set the Load type to SPC. 4. Create the first constraint. a) Using the nodes selector, select the node at one end of the bushing. b) Select the degrees of freedom, dof1-dof3; unselect all others. Dofs with a check will be constrained, while dofs without a check will be free. Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom. Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom.

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c) Click create. A constraint is created. A constraint symbol (triangle) appears at the selected node. The number 123 is displayed beside the constraint symbol, indicating that dof1, dof2 and dof3 are constrained.

Figure 537: Constraining dof1, dof2 and dof3 at One End of the Bushing

5. Create the second constraint. a) Using the nodes selector, select the node at the other end of the bushing. b) Select the degrees of freedom, dof2 and dof3; unselect all others. c) Click create.

Figure 538: Constraining dof2 and dof3 at the Other End of the Bushing

6. Create the third constraint. a) Double-click nodes and select by id, then enter 3239. Node ID 3239 is selected, which corresponds to the shock absorber mounting location. b) Select the degree of freedom, dof3; unselect all others. c) Click create.

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Figure 539: Constraining dof3 on Node ID 3239

7. Click return.

Applying Forces to the Brake, Corner and Pothole Loadcases 1. From the Analysis page, click forces. 2. Apply a force to the Brake load case. a) From the Model Browser, Load Collectors folder, right-click on Brake and select Make Current from the context menu. b) Double-click the nodes and select by id, then enter 2699. c) In the magnitude= field, enter 1000. d) Set the vector selector to x-axis. e) Click create. An arrow, pointing in the x direction, appears at the selected node. Tip: For better visualization of the forces, in the uniform size= field, enter 100. 3. Apply a force to the Corner load case. a) From the Model Browser, Load Collectors folder, right-click on Corner and select Make Current from the context menu. b) Double-click the nodes and select by id, then enter 2699. c) In the magnitude= field, enter 1000. d) Set the vector selector to y-axis. e) Click create.

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OptiStruct Tutorials Topology Optimization An arrow, pointing in the y direction, appears at the selected node. 4. Apply a force to the Pothole load case. a) From the Model Browser, Load Collectors folder, right-click on Pothole and select Make Current from the context menu. b) Double-click the nodes and select by id, then enter 2699. c) In the magnitude= field, enter 1000. d) Set the vector selector to z-axis. e) Click create. An arrow, pointing in the z direction, appears at the selected node. 5. Click return to go back to the Analysis page.

Figure 540: Forces Applied to the Brake, Corner and Pothole Loadcases For better visualization of the forces, the design component is turned off using the Display panel.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter Brake.

3. Set Analysis type to linear static. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select SPC and click OK. 5. Define LOAD. a) For LOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select Brake and click OK. 6. Repeat the above steps to create load steps named Corner and Pothole.

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a) For the Corner load step, set SPC to SPC and LOAD to Corner. b) For the Pothole load step, set SPC to SPC and LOAD to Pothole.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter design_prop. 5. Set type: to PSOLID.

6. Using the props selector, select design_prop. 7. Click create. 8. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter vol.

b) Below response type, select volume. c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter disp1.

b) Below response type, select static displacement. c) Using the nodes selector, select the 2699. d) Click nodes > by id, then enter 2699 in the id= field. e) Set the displacement type to total disp. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

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p.556 Resultant of the rotational displacements in x, y, and z directions.

f) Click create. 5. Click return to go back to the Optimization panel.

Creating Constraints on Displacement Responses In this step you will define the upper and lower bound constraint criteria for this analysis. 1. Click the Dconstraints panel. 2. Create the first constraint. a) In the constraint= field, enter constr1.

b) Check the box next to upper bound, then enter 0.05. c) Click response= and select disp1.

d) Using the loadsteps selector, select Brake. e) Click create. 3. Create the second constraint. a) In the constraint= field, enter constr2.

b) Check the box next to upper bound, then enter 0.02. c) Click response= and select disp1.

d) Using the loadsteps selector, select Corner. e) Click create. 4. Create the third constraint. a) In the constraint= field, enter constr3.

b) Check the box next to upper bound, then enter 0.05. c) Click response= and select disp1.

d) Using the loadsteps selector, select Pothole. e) Click create. 5. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select vol. 4. Click create. 5. Click return twice to exit the Optimization panel.

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Checking the Optimization Problem A check run may be performed in which OptiStruct will estimate the amount of RAM and disk space required to run the model. During the check run, OptiStruct will also scan the deck checking that all the necessary information required to perform an analysis or optimization is present and also that this information is not conflicting. 1. From the Analysis page, click the OptiStruct panel. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter carm_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to check. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. When the processing is complete, view the file carm_complete.out. This is the OptiStruct output file containing specific information on the file setup, optimization problem setup, RAM and disk space requirement for the run. Review the different sections of this file for possible warnings and errors. Is the optimization problem set up correctly? Refer to the Optimization Problem Parameters section. Is the objective function set up correctly? Refer to the Problem Parameters section. Are the constraints set up correctly? Refer to the Optimization Problem Parameters section. What is the recommended amount of RAM for an In-Core solution? Refer to the Memory Estimation Information section. Is there enough disk space to run the optimization? Refer to the Disk Space Estimation Information section.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter carm_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog.

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5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file carm_complete.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: carm_complete.res HyperMesh binary results file. carm_complete.HM.comp.cmf HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. carm_complete.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the carm_complete.fem file. carm_complete.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. carm_complete.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. carm_complete.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. carm_complete.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. carm_complete.his_data The OptiStruct history file containing iteration number, objective function values and percent of constraint violation for each iteration. carm_complete.HM.ent.cmf HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs.

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carm_complete.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration.

Viewing the Results Element density results are output to the carm_complete_des.h3d file from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iterations by default into carm_complete_s#.h3d files, where # specifies the sub case ID.

Viewing the Deformed Structure Viewing the deformed shape of a model helps you to determine if the boundary conditions are defined correctly, and also to find out if the model is deforming as expected. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and loads all three .h3d files in a different page of HyperView. The analysis results are available in pages 2, 3, and 4. The first page contains the optimization results. 2. In the top, left of the application click

to move to the third page.

The second page has the results from the carm_complete_s1.h3d file. The name of the page is displayed as Subcase 1 - Brake to indicate that the results correspond to subcase 1. 3. From the Animation toolbar, set the animation mode to linear (

).

4. Define contour settings. a) From the Results toolbar, click

to open the Contour panel.

b) Under Result type, select Displacement [v] and Mag. c) Click Apply to display the displacement contour. 5. Define the deformed shape settings. a) From the Results toolbar, click

to open the Deformed panel.

b) Under Deformed shape, set Result type to Displacement (v), set Scale to Model units, set Type to Uniform, and enter 10 in the Value field.

Specifying a Value of 10 indicates that the maximum displacement will be 10 Model units and all other displacements will be proportional.

c) Under Undeformed shape, set Show to Wireframe. d) Click Apply. A deformed plot of your model with displacement contour should be visible, overlaid on the original undeformed mesh. 6. From the Animation toolbar, click

(Start/Pause) to animate the model.

A deformed animation for the first subcase (brake) should be displayed.

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Analyze the following: • In what direction is the load applied for the first subcase? • Which nodes have degrees of freedom constrained? • Does the deformed shape look correct for the boundary conditions applied to the mesh? 7. In the Results browser, select Iteration 18. The contour now shows the displacement results for Subcase 1 (brake) and iteration 18 which corresponds to the end of the optimization iterations.

Figure 541:

8. From the Animation toolbar, click

to stop the animation.

9. In the top, right of the application click

to move to the third page.

The third page has results loaded from carm_complete_s2.h3d file. The name of the page is displayed as Subcase 2 - corner to indicate that the results correspond to subcase 2. 10. Repeat the above steps to display the displacement contours and deformed shape of the model for the second subcase. Analyze the following: • In what direction is the load applied for the second subcase? • Which nodes have degrees of freedom constrained? • Does the deformed shape look correct for the boundary conditions applied to the mesh? 11. Similarly, review the displacements and deformation for subcase 3 (pothole).

Reviewing the Contour Plot of the Density Results The optimization iteration results (Element Densities) are loaded in the second page. 1. In the top, right of the application click

to go back to the Design History page.

2. Define contour settings. a) On the Results toolbar, click

to open the Contour panel.

Notice: The Result type is set to Element Densities (s) and Density. This should be the only result type in the carm_complete_des.h3d file. b) Set Averaging method to Simple. c) Click Apply.

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The density contour displays. The contour is all blue because your results are on the first design step or Iteration 0. 3. In the Results browser, select Iteration 18. Each element of the model is assigned a legend color, indicating the density of each element for the selected iteration. Analyze the following: Have most of your elements converged to a density close to 1 or 0? If there are many elements with intermediate densities, the DISCRETE parameter may need to be adjusted. The DISCRETE parameter (set in the opti control panel on the optimization panel) can be used to push elements with intermediate densities towards 1 or 0 so that a more discrete structure is given. In this model, refining the mesh should provide a more discrete solution; however, for the purposes of this tutorial, the current mesh and results are sufficient. Regions that need reinforcement tend towards a density of 1.0. Areas that do not need reinforcement tend towards a density of 0.0. Does the max= field show 1.0e+00? In this case, it is. If it is not, the optimization has not progressed far enough. Allow more iterations and/or decrease the OBJTOL parameter (also set in the Opti control panel). If adjusting the discrete parameter, refining the mesh, and/or decreasing the objective tolerance does not yield a more discrete solution (none of the elements progress to a density value of 1.0), review the set up of the optimization problem. Some of the defined constraints may not be attainable for the given objective function (or vice versa).

Viewing an Iso Value Plot of Element Densities An Iso Value plot provides the information about the element density. Iso Value retains all of the elements at and above a certain density threshold. Pick a density threshold that provides a structure that suits your needs. 1. From the menu bar, click Results > Plot > Iso. 2. In the Iso panel, set Result type to Element Densities (s). 3. Click Apply. 4. Change the density threshold. • In the Current value field, enter 0.15. • Under Current value, move the slider.

The Iso value in the modeling window updates interactively when you enter a new value or move the slider. This feature is useful when you want to get a better look at the material layout and the load paths from OptiStruct.

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Figure 542:

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OS-T: 2020 Increasing Natural Frequencies of an Automotive Splash Shield with Ribs In this tutorial you will generate a preliminary design of stiffeners in the form of ribs for an automotive splash shield. The objective is to increase the natural frequency of the first normal mode using topology to identify locations for ribs in the designable region.

Figure 543: Finite Element Mesh The finite element mesh contains designable (red) and non-designable (blue) material.

The optimization problem for this tutorial is stated as: Objective

Maximize frequency of mode number 1.

Constraint

Upper bound constraint of 40% for the designable volume.

Design Variables

Density of each element in the design space.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the sshield_opti.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Applying Loads and Boundary Conditions Creating Load Collectors 1. Create the Constraints load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter constraints.

c) Click Color and select a color from the color palette. d) Set Card Image to None. 2. Create the EIGRL load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter EIGRL.

c) Click Color and select a color from the color palette. d) Set Card Image to EIGRL. e) For V2, enter 3000. f) For ND, enter 2.

This load collector defines data needed to perform real eigenvalue analysis (vibration or buckling) and specified the solver to calculate the first two modes between a frequency range of 0 and 3000 Hz.

Creating Constraints In this step you will create constraints at bolt locations.

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1. From the Model Browser, Load Collectors folder, right-click on Constraints and select Make Current from the context menu. 2. From the Analysis page, click constraints. 3. Select the Create subpanel. 4. Double-click nodes and select by id, then enter 1075, 1076 in the id= field. 5. Constrain all dofs.

Dofs with a check will be constrained, while dofs without a check will be free. Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom. Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 6. Click create. 7. Click return to go to the main menu. Two constraints are now created. Constraint symbols (triangles) appear at the selected nodes. The number 123456 is displayed beside the constraint symbol, indicating that all dofs are constrained.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter frequencies.

3. Set Analysis type to normal modes. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select constraints and click OK. 5. Define METHOD(STRUCT). a) For METHOD(STRUCT), click Unspecified > Loadcol. b) In the Select Loadcol dialog, select EIGRL and click OK.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 544: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter sshield_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Clear the options field. 9. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the sshield_analysis.fem was written. The sshield_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: sshield_analysis.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. sshield_analysis.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. sshield_analysis.h3d HyperView binary results file. sshield_analysis.res HyperMesh binary results file. sshield_analysis.stat Summary, providing CPU information for each step during analysis process.

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sshield_analysis.mvw HyperView session file. sshield_analysis_frames.html HTML file used to post-process the .h3d with HyperView Player using a browser. It is linked with the _menu.html file. sshield_analysis_menu.html HTML file to post-process the .h3d with HyperView Player using a browser.

Viewing the Results Eigenvector results are output from OptiStruct for a normal modes analysis by default. This section describes how to view the results in HyperView. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of page 2 of HyperMesh Desktop, and displays the sshield_analysis.mvw session file, which is linked with the sshield_analysis.h3d file. 2. From the Animation toolbar, set the animation mode to

(Modal).

3. In the Results browser, click Mode 1. The browser shows the first two natural frequencies calculated between 0 and 3000Hz.

Figure 545:

4. Define deformed settings. a) From the Results toolbar, click

to open the Deformed panel.

b) Set Result type to Eigen mode (v). c) Set Scale to Model Units. d) Set Type to Uniform. e) In the Value field, enter 10. f) Click Apply.

5. Animate the model. a) From the Animation toolbar, click

.

b) Move the Max Frame Rate slider between 60 and 1 to increase or decrease the animation speed.

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Tip: You can also change the default values for Angular Increment to refine your animation. c) Click

to start the animation.

An animation of the mode shape should be seen for the first frequency. d) Click

to stop the animation.

6. On the Page Control toolbar, click the Page Delete icon to delete the HyperView page.

Figure 546:

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter shield. 5. Set type: to PSHELL.

6. Using the props selector, select design. 7. For base thickness, enter 0.300. 8. Click create.

A topology design space definition, shield, has been created. All elements referring to the design property collector (elements organized into the "design" component collector) are now included in the topology design space. The thickness of these shells can vary between 0.300 (base thickness) and the maximum thickness defined by the T (thickness) field on the PSHELL card. The object of this exercise is to determine where to locate ribs in the designable region. Therefore, a non-zero base thickness is defined, which is the original thickness of the shells. The maximum thickness, which is defined by the T field on the PSHELL card, should be the allowable depth of the rib. Currently, the T field on the PSHELL card is still set to 0.300 (the original shell thickness). You will change this to 1.0 so that the ribs of a maximum height of 0.7 units can be obtained by the topology optimization. 9. Click return. 10. Edit the thickness of the design property. a) In the Model Browser, Properties folder, click design.

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OptiStruct Tutorials Topology Optimization b) In the Entity Editor, T field, enter 1.000.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the frequency response. a) In the responses= field, enter freq1.

b) Below response type, select frequency. c) For Mode Number, enter 1.0.

d) Using the loadsteps selector, select frequencies. e) Click create. A response, freq1, is defined for the frequency of the first mode extracted. 5. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that max is selected. 3. Click response= and select freq1. 4. Using the loadsteps selector, select frequencies. 5. Click create. 6. Click return twice to exit the Optimization panel.

Defining Constraints A response defined as the objective cannot be constrained. In this case, you cannot constrain the response freq1. An upper bound constraint needs to be defined for the response volfrac. 1. Click dconstraints. 2. In the constraint= field, enter volume_constr.

3. Check the box next to upper bound, then enter 0.40. 4. Click response = and select volfrac. 5. Click create.

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6. Click return to return to the Optimization panel. A constraint is defined on the response volfrac. The constraint is an upper bound with a value of 0.40. The constraint applies to all subcases as the volumefrac response is a global response. In this step you are allowing the topology optimization to use additional volume with which it can come with ribsvconstr.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter sshield_optimization for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file sshield_optimization.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: sshield_optimization.mvw HyperView session file. sshield_optimization.HM.comp.cmf HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. sshield_optimization.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the sshield_optimization.fem file. sshield_optimization.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run.

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sshield_optimization.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. sshield_optimization.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. sshield_optimization.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. sshield_optimization.his_data The OptiStruct history file containing iteration number, objective function values and percent of constraint violation for each iteration. sshield_optimization.HM.ent.cmf HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs. sshield_optimization.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. sshield_optimization_frame.html HTML file used to post-process the .h3d with HyperView Player using a browser. It is linked with the _menu.html file. sshield_optimization_menu.html HTML file used to post-process the .h3d with HyperView Player using a browser. sshield_optimization_des.H3D HyperView binary results file that contains: Density results from topology optimizations, Shape results from topography or shape optimizations and Thickness results from size and topology optimizations. sshield_optimization_s1.H3D HyperView binary results file that contains: Displacement results from linear static analysis, Element strain energy results from normal mode analysis and Stress results from linear static analysis, etc.

Viewing the Results With topology optimization of shell elements, Element Density and Element Thickness results are output from OptiStruct for all iterations. In addition, Eigenvector results are output for the first and last iterations by default. This section describes how to view those results in HyperView. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and loads the session file sshield_optimization.mvw that is linked with the sshield_optimization_des.h3d and the sshield_optimization_s1.h3d.

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p.572 to open the Contour panel.

3. Set the Result type: to Element Thickness(s). 4. Click Apply. 5. From the Results Browser, select the last iteration.

Figure 547:

Each element of the model is assigned a legend color, indicating the thickness of each element for the selected iteration. Analyze the following: Have most of your elements converged to a thickness close to 1 or 0? If there are many elements with intermediate densities (represented by intermediate thickness), the discrete parameter may need to be adjusted. The DISCRETE parameter (set in the Opti control panel on the Optimization panel) can be used to push elements with intermediate densities towards 1 or 0 so that a more discrete structure is given. Regions that need reinforcement tend towards a density of 1.0. Areas that do not need reinforcement tend towards a density of 0.0. Is the max = field showing 1.0e+00? In this case, it is. If it is not, the optimization has not progressed far enough. Allow more iterations and/or decrease the OBJTOL parameter (set in the Opti control panel). If adjusting the DISCRETE parameter, incorporating a checkerboard control, refining the mesh, and/or decreasing the objective tolerance does not yield a more discrete solution (none of the elements progress to a density value of 1.0), you may want to review the set up of the optimization problem. Some of the defined constraints may not be attainable for the given objective function (or visa-versa).

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Figure 548: Contour Plot of Element Densities at iteration 6 All components are displayed except the designable component. The top view of the model is displayed.

Where would you place your ribs? 6. On the Page Control toolbar, click the Page Delete icon to delete the HyperView page.

Figure 549:

Setting Up the Final Normal Modes Analysis Based on the topology results obtained above, a number of ribs were added to the model. The new design sshield_newdesign.fem, which includes these ribs can be found in the optistruct.zip file.

Deleting the Current Model 1. In HyperMesh, click return to exit the OptiStruct panel. 2. From the menu bar, click File > New > Model. 3. Click Yes to clear the current session.

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Deleting the current model clears the current HyperMesh database. Information stored in .hm files on your disk is not affected.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the sshield_newdesign.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 550: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter sshield_newdesign for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Clear the options field.

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9. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the sshield_newdesign.fem was written. The sshield_newdesign.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: sshield_newdesign.html HTML report of the analysis, providing a summary of the problem formulation and the analysis results. sshield_newdesign.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. sshield_newdesign.h3d HyperView binary results file. sshield_newdesign.res HyperMesh binary results file. sshield_newdesign.stat Summary, providing CPU information for each step during analysis process. sshield_newdesign.mvw HyperView session file. sshield_newdesign_frames.html HTML file used to post-process the .h3d with HyperView Player using a browser. It is linked with the _menu.html file. sshield_newdesign_menu.html HTML file to post-process the .h3d with HyperView Player using a browser.

Viewing the Results 1. From the OptiStruct panel, click HyperView. This launches HyperView in the HyperMesh Desktop and loads the file sshield_newdesign.mvw that is linked with the file sshield_newdesign.h3d. 2. Set the animation mode to

(Modal).

3. In the Results Browser, select Mode 1. 4. Click

to open the Defomed panel.

5. Make or verify the following settings in the Deformed panel. Result Type

Eigen mode (v)

Scale

Model Units

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Type

Uniform

Value

10

6. Click Apply. 7. Click

to start the animation.

An animation of the mode shape should be seen for the first frequency. 8. Click

again to stop the animation.

Comparing Results What is the percentage increase in frequency for your first mode (sshield_analysis.fem vs. sshield_newdesign)? You have seen that the frequency of the structure for the first mode has increased from 43.63 Hz to 84.88 Hz. How much mass has been added to the part (check the mass of your ribs in the mass calc panel in the Tool page)? What is the percentage increase in mass?

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OS-T: 2030 Control Arm with Draw Direction Constraints In this tutorial you will perform a topology optimization using draw direction constraints on a control arm. The finite element mesh contains designable (brown) and non-designable regions (blue) is shown in Figure 551.

Figure 551: Control Arm Schematic

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the controlarm.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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3. Click Open. The controlarm.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter dv1. 5. Set type: to PSOLID.

6. Using the props selector, select Design. 7. Click create.

Creating Draw Direction Constraints The draw direction constraints allow the casting feasibility of the design so that the topology determined will allow the die to slide in a given direction. These constraints are defined using the DTPL card. Two DRAW options are available. The option 'SINGLE' assumes that a single die will be used. The option 'SPLIT' assumes that two dies splitting apart in the given draw direction will be used to cast the part. 1. Select the draw subpanel. 2. Set draw type: to single. The option 'SINGLE' assumes that a single die will be used and it slides in the given drawing direction. 3. Define the drawing direction. a) Click anchor node, and enter 3209 in the id= field. b) Click first node, and enter 4716 in the id= field.

4. Using the props selector, select the Non-design property. The non-designable parts are selected as obstacles for the casting process on the same DTPL card, and the casting feasibility of the final structure is persevered. 5. Click update. 6. Click return to go back to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization.

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OptiStruct Tutorials Topology Optimization 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to by entity and no regionid. d) Click create. 4. Create the weighted component response. a) In the responses= field, enter Comp1.

b) Below response type, select weighted comp. c) Click loadsteps, then select all loadsteps. d) Click return. e) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter Constr. 3. Click response = and select Volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select Compl. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter controlarm_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file controlarm_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: controlarm_opt.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. controlarm_opt.hist The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history. controlarm_opt.HM.comp.tcl HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. controlarm_opt.HM.ent.tcl HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs. controlarm_opt.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. controlarm_opt.mvw HyperView session file. controlarm_opt.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. controlarm_opt.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the controlarm_opt.fem file. controlarm_opt.res HyperMesh binary results file.

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controlarm_opt.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. controlarm_opt.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. controlarm_opt_des.h3d HyperView binary results file that contain optimization results. controlarm_opt_frame.html HTML file used to post-process the .h3d with HyperView Player using a browser. It is linked with the _menu.html file. controlarm_opt_hist.mvw Contains the iteration history of the objective, constraints, and the design variables. It can be used to plot curves in HyperGraph, HyperView, and MotionView. controlarm_opt_menu.html HTML file used to post-process the .h3d with HyperView Player using a browser. controlarm_opt_s#.h3d HyperView binary results file that contains from linear static analysis, and so on.

Viewing the Results Element density results are output to the controlarm_opt_des.h3d file from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iterations by default into controlarm_opt_s#.h3d files, where # specifies the sub case ID.

Reviewing the Contour Plot of Element Densities 1. From the OptiStructpanel, click HyperView. 2. In the Results Browser, select the last iteration. 3. From the Results toolbar, click

to open the Contour panel.

4. Under Result type, select Element densities (s) and Density. 5. Set the Averaging method: to Simple. 6. Click Apply. The resulting contours represent the displacement field resulting from the applied loads and boundary conditions. In this model, refining the mesh should provide a more discrete solution; however, for the sake of this tutorial, the current mesh and results are sufficient.

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Setting Iso Plot of Densities The iso surface feature can be a very useful tool for post-processing density results from OptiStruct. For models with solid design regions, this feature becomes a vital tool for analyzing density results. 1. In the Results Browser, verify the last iteration is still selected. 2. From the Results toolbar, click

to open the Iso Value panel.

3. Set the Result type: to Element Densities (s). 4. Click Apply. 5. Change the density threshold. • In the Current value field, enter 0.3.

• Under Current value, move the slider. 6. Set Show values to Above. 7. Under Clipped geometry, select Features and Transparent. Figure 552:

Figure 553: Isosurface Plot of Element Densities

Viewing Contour Plot of Displacements and Stresses 1. In the top, right of the application, click

to proceed to the results of Load Case 1 on page 3.

2. On the Animation toolbar, set the animation mode to 3. On the Results toolbar, click

(Linear Static).

to open the Contour panel.

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4. Set the Result type: to Displacements (v). 5. Click Apply. The displacement plot for Iteration 0 displays. 6. In the Results Browser, set the iteration to the last iteration.

Figure 554: Displacement Plot for the Last Iteration

A displacement plot for the last iteration displays. The stress results are also available for the respective iterations.

Figure 555: Displacement Contour for the First Loadstep at the Last Iteration

7. Similarly, view the results for Load Case 2 on page 4.

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Figure 556: Displacement Contour for the Second Loadstep at the Last Iteration

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OS-T: 2040 Spot Weld Reduction using CWELD and 1D In this tutorial you will perform a 1D topology optimization. The model used in this tutorial is a simple welded hat section. The welding is modeled using CWELD elements. The objective of this tutorial is to minimize the weighted compliance through all three load cases. The volume fraction of the weld component is limited to 0.3. The design space is the spot weld component.

Figure 557:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the hut.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

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3. Click Open. The hut.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter tpl. 5. Set type: to PWELD.

6. Using the props selector, select PWELD_500. 7. Click create. 8. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to by entity and no regionid. d) Using the props selector, select PWELD_500. e) Click create. 4. Create the weighted component response. a) In the responses= field, enter wcomp.

b) Below response type, select weighted comp. c) Click loadsteps, then select all loadsteps. d) Change the weighting factors for SUBCASE200 and SUBCASE300 to 100.0.

This increases the influence of the two bending load cases vs. the torsion load case SUBCASE1, which remains at 1.0.

e) Click return. f) Click create. 5. Click return to go back to the Optimization panel.

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Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter volfrac. 3. Click response = and select Volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select wcomp. 4. Click create. 5. Click return twice to exit the Optimization panel.

Modifying Optimization Parameters To achieve good results, some optimization parameters need to be modified. 1. Click the opti control subpanel. 2. Check the box next to DISCRT1D =, then enter 20.0.

This increases the penalty factor in the density method only for the 1D elements to achieve a discrete result.

3. Check the check box next to OBJTOL =, then enter 1.e-5.

This reduces the objective tolerance that is checked for convergence.

4. Click return twice.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter hut_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file hut_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file. 9. Click Close.

Viewing the Results In this step you will visualize the new spot weld configuration. To post-process the results, the weld elements will be sorted by density into different components. 1. From the menu bar, click File > Run > Command File. 2. In the Open Command File dialog, open the hut_opt.HM.comp.tcl output file from your OptiStruct run. Four of the welds are in the DENS 0.9-1.0 component; all others are in the DENS 0.0-0.1 component. 3. To do a re-analysis with the new weld configuration, undisplay the components with low density (DENS 0.0-0.1 to DENS 0.8-0.9) and rerun the analysis with export options: set to displayed in the OptiStruct panel.

Figure 558: Final Configuration

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OS-T: 2050 Pattern Repetition In this tutorial you will perform a topology optimization using pattern repetition. The model used in this tutorial is a rectangular plate with a concentrated force on one edge and two constraints on the opposite edge. Two other rectangular plates with a scaled size of 0.6 and 0.3 from the original plate, with forces and boundary conditions applied in different directions, are also modeled to highlight the difference between the topology results with and without pattern repetitions. The objective of this tutorial is to minimize the compliance for the single subcase. The volume fraction of the design space is limited to 0.3. The design spaces are the three plates.

Figure 559:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the no_repeat.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter dv1. 5. Set type: to PSHELL.

6. Using the props selector, select first. 7. Click create. 8. Update the design variable's parameters. a) Select the parameters subpanel. b) Toggle minmemb off to mindim=, then enter 2.0. c) Click update.

9. Repeat the above steps to create design variables labeled dv2 and dv3 for the second and third component. 10. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac.

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c) Set regional selection to total and no regionid. d) Click create. 4. Create the compliance response. a) In the response= field, enter comp.

b) Below response type, select compliance. c) Set regional selection to total and no regionid. d) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter volfrac. 3. Click response = and select Volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select comp. 4. Using the loadsteps selector, select sub. 5. Click create. 6. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter no_repeat_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file no_repeat_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Without Pattern Repetition In this step you will review an Iso Value plot of element densities. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and loads the session file no_repeat_opt.mvw that is linked with the no_repeat_opt_des.h3d file. 2. On the Results toolbar, click

to open the Iso Value panel.

3. Under Result type, select Element Densities(s). 4. On the Animation toolbar, click

to choose the last iteration from the Simulation list.

5. Click Apply. 6. Change the density threshold. • In the Current value field, enter 0.4.

• Under Current value, move the slider. 7. Set Show values to Above. 8. Under Clipped geometry, select Features and Transparent. An isosurface plot is displayed. The elements with a density greater than the value of 0.4 are shown in color, the rest are transparent.

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Figure 560:

9. On the Page Controls toolbar, click the Delete Page icon to delete the HyperView page.

Figure 561:

Setting Up Pattern Repetition In this step you will define the pattern repetition cards in HyperMesh. 1. Select nodes. a) From the Tool page, click the numbers panel. b) Click nodes > by id, then enter 1329, 66, 6, 46, 507, 447, 487, 928, 892, 948 in the id= field. Use commas to seperate the values. c) Click on. d) Click return to exit the Numbers panel. The selected node's numbers display. 2. Isolate component collectors. a) From the menu bar, click View > Browsers > HyperMesh > Mask to open the Mask Browser. b) In the Mask Browser, Isolate column, click 1 to display only component collectors.

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Figure 562:

3. From the Analysis page, click the optimization panel. 4. Click the topology panel. 5. Select the pattern repetition subpanel. 6. Create the master DTPL card.

a) Double-click desvar= and select dv1. b) Set the switch to master. c) Toggle from system to coordinates. d) Using the first selector, select node ID 6. e) Using the second selector, select node ID 46. f) Using the third selector, select node ID 1329. g) Using the anchor selector, select node ID 66. h) Click update.

7. Create the slave DTPL card.

a) Double-click desvar= and select dv2. b) Set the switch to slave. c) Set master= to dv1. d) For sx=, enter 0.6; for sy=, enter 0.6; for sz=, enter 1.0. e) Toggle from system to coordinates.

f) Using the first selector, select node ID 447. g) Using the second selector, select node ID 487. h) Using the third selector, select node ID 1329. i) Using the anchor selector, select node ID 507. j) Click update. 8. Create the slave DTPL card.

a) Double-click desvar= and select dv3. b) Set the switch to slave. c) Set master= to dv1. d) For sx=, enter 0.3; for sy=, enter 0.3; for sz=, enter 1.0. e) Toggle from system to coordinates.

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f) Using the first selector, select node ID 892. g) Using the second selector, select node ID 928. h) Using the third selector, select node ID 1329. i) Using the anchor selector, select node ID 948. j) Click update. 9. To view the card image of the DTPL card, right-click on any of the design variables in the Model Browser and select Card Edit from the context menu.

Figure 563: Card Image for dv2

10. Click return twice. You have identified the first DTPL card with ID 1 (on the first component) as the master, and the DTPL's of ID 2 (second component) and ID 3 (third component) as the slaves, which are dependent on the DTPL of ID1. The second component is scaled 0.6 in both the x- and y-axis, while the third component is scaled 0.3 in both the x- and y-axis with respect to the first component.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter repeat_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file repeat_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

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9. Click Close.

Viewing the Results With Pattern Repetition In this step you will review an Iso Value plot of element densities. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and loads the session file repeat_opt.mvw that is linked with the repeat_opt_des.h3d file. 2. On the Results toolbar, click

to open the Iso Value panel.

3. Under Result type, select Element Densities(s). 4. On the Animation toolbar, click

to choose the last iteration from the Simulation list.

5. Click Apply. 6. Change the density threshold. • In the Current value field, enter 0.38. • Under Current value, move the slider. 7. Set Show values to Above. 8. Under Clipped geometry, select Features and Transparent. An isosurface plot is displayed. The elements with a density greater than the value of 0.38 are shown in color, the rest are transparent.

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Figure 564:

9. On the Page Controls toolbar, click the Delete Page icon to delete the HyperView page.

Figure 565:

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OS-T: 2060 Symmetry and Draw Direction Constraints Applied Simultaneously In this tutorial you will perform a topology optimization on an automotive control arm with the simultaneous application of symmetry and draw direction constraints. This tutorial uses the same optimization problem considered in OS-T: 2010 Design Concept for an Automotive Control Arm, except that a refined mesh will be used in order to better capture the effect of applying symmetric and draw manufacturing constraints simultaneously. The finite element mesh of the structural model containing the designable (blue) and the non-designable (red) regions, along with the loads and constraints applied.

Figure 566:

The optimization problem is stated as: Objective

Minimize volume.

Constraints

SUBCASE 1: The resultant displacement of the point where loading is applied must be less than 0.05 mm. SUBCASE 2: The resultant displacement of the point where loading is applied must be less than 0.02 mm. SUBCASE 3: The resultant displacement of the point where loading is applied must be less than 0.04 mm.

Design Variables

Element density.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh.

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The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the carm_draw_symm.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Define the Symmetry and Draw Direction Manufacturing Constraints 1. From Analysis page, click the optimization panel. 2. Click the topology panel. 3. Defining minimum member size. a) Click review and select solid. b) Select the parameters subpanel. c) Toggle minmemb off to mindim, and enter 16.0.

This forces the diameter or thickness of any structural member to be higher than 16 mm; if this is not user-set, OptiStruct automatically selects a minimum member size based on the average mesh size (if a manufacturing constraint is selected).

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Figure 567:

d) Click update to confirm the minimum member size set up. 4. Defining the draw direction. a) Select the draw subpanel. b) Set draw type to single. c) Using the anchor node and first node selectors, select the nodes indicated in Figure 568. Together, these two nodes define a vector in the positive Z direction. This defines that the die draw direction is along the positive Z direction.

Figure 568:

d) Using the obstacle: props selector, select the nondesign property. 5. Define the symmetry constraint. a) Select the pattern grouping subpanel. b) Set the pattern type to 1-pln sym. c) Click anchor node, and enter 1 in the id= field. The node with the ID of 1 is selected. d) Click first node, and enter 2 in the id= field. The node with the ID of 2 is selected. e) Click update. Together, these two nodes define a vector in the negative Z direction. Hence, the symmetry plane is defined as the plane perpendicular to the Z-axis (which is the same as the Y-Z plane), and passing through the anchor node.

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6. Click return twice to go back to the Analysis page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter carm_draw_symm_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Toggle memory options to upper limit in Mb and enter 2000.

8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file carm_draw_symm_complete.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Element density results are output to the carm_draw_symm_complete_des.h3d file from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iterations by default into carm_draw_symm_complete_s#.h3d files, where # specifies the sub case ID.

Reviewing the Contour Plot of the Density Results It is helpful to view the deformed shape of a model to determine if the boundary conditions are defined correctly, and also to find out if the model is deforming as expected. The analysis results are available in pages 2, 3, and 4. The optimization iteration results (Element Densities) are loaded in the first page. 1. From the OptiStruct panel, click HyperView. HyperView launches inside of HyperMesh Desktop, and all three .h3d files are loaded in a different page.

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2. In the top, right of the application, click

to return to the Design History page, indicating that

the results correspond to optimization iterations. 3. From the Results toolbar, click

to open the Contour panel.

4. Verify that the Result type is set to Element Densities[s] and Density. This should be the only result type in the carm_draw_symm_complete_des.h3d file.

5. Set the Averaging method to Simple.

6. Click Apply to display the density contour. The contour is all blue because the results are on the first design step or Iteration 0. 7. In the Results Browser, select the last iteration listed. Each element of the model is assigned a legend color, indicating the density of each element for the selected iteration.

Figure 569:

Viewing an Iso Value Plot of Element Densities An Iso Value plot provides the information about the element density. Iso Value retains all of the elements at and above a certain density threshold. Pick the density threshold providing the structure that suits your needs. 1. From the Results toolbar, click

to open the Iso Value panel.

2. Set the Result type to Element Densities.

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3. Click Apply. An Iso Plot displays. 4. Change the density threshold. • In the Current value field, enter 0.2.

• Under Current value, move the slider. When you update the density threshold, the Iso value displayed in the modeling window updates interactively. Use this tool to get a better look at the material layout and the load paths from OptiStruct. The parts of the model with densities greater than the specified value of 0.2 display.

Figure 570: Iso Value Plot of Element Densities

Review questions: Have most of your elements converged to a density close to 1 or 0? If there are many elements with intermediate densities, the DISCRETE parameter may need to be adjusted. The DISCRETE parameter (set in the opti control panel on the Optimization panel) can be used to push elements with intermediate densities toward 1 or 0, so that a more discrete structure is given. In this model, refining the mesh should provide a more discrete solution; however, for the purposes of this tutorial, the current mesh and results are sufficient. Regions that need reinforcement tend towards a density of 1.0. Areas that do not need reinforcement tend towards a density of 0.0. Is the max= field showing 1.0e+00? In this case, it is. If it is not, the optimization has not progressed far enough. Allow more iterations and/or decrease the OBJTOL parameter (also set in the opti control panel).

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If adjusting the discrete parameter, refining the mesh, and/or decreasing the objective tolerance does not yield a more discrete solution (none of the elements progress to a density value of 1.0), review the set up of the optimization problem. Some of the defined constraints may not be attainable for the given objective function (or vice versa). Has the volume been minimized for the given constraints? Have the displacement constraints been met?

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OS-T: 2070 Reduced Model using DMIG In this tutorial an existing finite element model of a simple cantilever beam is used to demonstrate how to reduce the finite element model using static reduction. You will also perform a topology optimization on the reduced model.

Figure 571: Full Cantilever Beam Model Without Static Reduction

The optimization problem may be stated as: Objective

Minimize compliance.

Constraints

Upper bound constraint of 40% for the designable volume.

Design Variables

The density for each element in the design space.

Figure 572: Topology Optimization Results for the Full Cantilever Beam Model

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The part to be reduced out of the model through the static reduction model reduction technique is referred to as a superelement. In OptiStruct, ASET or ASET1 Bulk Data Entries are required to indicate the boundary degrees of freedom of a superelement, meaning the set of degrees-of-freedom where the component (being replaced by direct matrix input) connects to the modeled structure. Both the accuracy and the cost of static reduction increase as the number of ASET entries is increased. For example, by using static reduction, the size of the matrix to solve will become smaller, but if the reduced matrix (DMIG) is very dense, then the solution time will become larger than the solution time for the full model where the matrix may be sparse. Hence, the selection of ASET entries is very important in performing an efficient analysis using DMIG. In order to prevent the reduced matrix from being too dense, ASET entries are chosen carefully (see the next figure) instead of creating ASET entries for all of the boundary nodes between the design and non design spaces. Due to the small size of the problem used for this tutorial, the selection of ASET entries may not affect the solution time.

Figure 573: ASET for the Cantilever Beam Model

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the cantilever_full.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The cantilever_full.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Generating a Superelement Creating ASETs Load Collector 1. Create a load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter Asets.

c) Set Card Image to None. 2. Create constraints. a) From the Analysis page, click the constraints panel. b) Select the create subpanel. c) Using the nodes selector, select boundary nodes.

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Figure 574:

d) Select all dofs. Dofs with a check will be assigned to the ASET. Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom. Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom. e) Click Load Type= and select ASET. f) Click create. 3. Click return to go to the main menu.

Deleting Elements Retained in the Subsequent Optimization The reduced stiffness matrix and load vector will be generated for only those elements that will be reduced out (superelement). Therefore, a new model needs to be created containing just the superelement part and the loads and boundary conditions applied directly to that part. 1. Press F2 to open the Delete panel. 2. Set the entity selector to elems, then click elems > by window. 3. Draw a window around the elements indicated in Figure 575.

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Figure 575:

4. Click delete entity. 5. Click return to go to the main menu.

Defining a Parameter to Write out Reduced Matrices to an External File The PARAM,EXTOUT bulk data entry is required to activate the matrix save process. Without this parameter, the run will proceed as normal. This parameter has two options: DMIGPCH, which will save the matrices in an ASCII format to a .pch file and DMIGBIN, which will save the matrices in a binary format to a .dmg file. DMIGPCH is used for this tutorial. 1. On the Analysis page, click the control cards panel. 2. In the Card Image dialog, click PARAM. 3. Select EXTOUT. 4. At the top of the card image, under the EXTOUT, select DMIGPCH. 5. Click return to exit PARAM. 6. Click return to get back to the main menu.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter cantilever_dmig.hm for the file name and save it to your working directory.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 576: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cantilever_dmig for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the cantilever_dmig.fem was written. The cantilever_dmig.out file is a good place to look for error messages that could help debug the input deck if any errors are present. The default files written to the directory are: cantilever_dmig.out OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each of the optimization iterations, and compute time information. Review this file for warnings and errors. cantilever_dmig.stat Summary of analysis process, providing CPU information for each step during analysis process. cantilever_dmig_AX.pch Reduced matrices (DMIG) file. The matrices are written to the .pch file with the same format as the DMIG bulk data entry. They are defined by a single header entry and one or more column entries. By default, the name of the stiffness matrix is KAAX, the mass is MAAX, and the load is PAX. Since mass matrix is not used in this tutorial, it is not written to .pch file. The I/O Option Entry, DMIGNAME, provides you with control over the name of the matrices.

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Clearing the Database From the menu bar, click File > New. The existing HyperMesh database is cleared.

Including the Superelement in the Model Opening the Model 1. Click File > Open > Model. 2. Select the cantilever_full.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The cantilever_full.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Deleting Superelement Part Reduced out using DMIG Since the matrices for the superelement part will be replaced by DMIG, the bulk data entries for the nodes and elements, as well as all loads and boundary conditions that are in the superelement, should be deleted. 1. Press F2 to open the Delete panel. 2. Set the entity selector to elems, then click elems > by window. 3. Draw a window around the elements indicated in Figure 577.

Figure 577:

4. Click delete entity. 5. Click return to go to the main menu.

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Setting up Topology Optimization with DMIG 1. On the Analysis page, click the control cards panel. 2. Define the INCLUDE_BULK control card. a) In the Card Image dialog, click INCLUDE_BULK. b) In the Include field, enter the file name cantilever_dmig_AX.pch.

The reduced matrices (DMIG) will be included in OptiStruct input deck. Here you are assuming that the topology optimization will be run in the same folder as the cantilever_dmig_AX.pch file. If you plan to run it in a different folder, then define the full path of this file.

c) Click return to exit the INCLUDE_BULK control card. 3. Define the K2GG control card. a) Click K2GG. b) In the K2GG= field, enter KAAX.

This specifies that the reduced stiffness matrix with the name KAAX has to be used (stored in the cantilever_dmig_AX.pch file).

c) Click return to exit the K2GG control card. 4. Define the P2G control card. a) Click P2G. b) In the P2G= field, enter PAX.

c) Click return to exit the P2G control card. 5. Click return to go to the main menu.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter topo. 5. Set type: to PSHELL.

6. Using the props selector, select design. 7. Click create. 8. Update the design variable's parameters. a) Select the parameters subpanel. b) Toggle minmemb off to mindim=, then enter 1.2. c) Click update. 9. Click return.

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Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the compliance response. a) In the response= field, enter Compl.

b) Below response type, select compliance. c) Set regional selection to total and no regionid. d) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter VFrac.

3. Click response = and select Volfrac. 4. Check the box next to upper bound, then enter 0.4. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select Compl. 4. Using the loadsteps selector, select step. 5. Click create. 6. Click return twice to exit the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model.

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2. In the Save As dialog, enter cantilever_opti.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter cantilever_opti for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file cantilever_opti.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: cantilever_opti.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. cantilever_opti.HM.comp.tcl HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. cantilever_opti.HM.ent.tcl HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs. cantilever_opti.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. cantilever_opti.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results.

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cantilever_opti.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the cantilever_opti.fem file. cantilever_opti.res HyperMesh binary results file. cantilever_opti.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. cantilever_opti.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. cantilever_opti_des.h3d HyperView binary results file that contain optimization results. cantilever_opti_s#.h3d HyperView binary results file that contains from linear static analysis, and so on.

Viewing the Results Element density results are output to the cantilever_opti_des.h3d file from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iterations by default into cantilever_opti_s#.h3d files, where # specifies the sub case ID.

Reviewing the Contour Plot of the Density Results 1. From the OptiStruct panel, click HyperView. 2. From the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Element Densities[s] and Density. 4. Set the Averaging method to Simple. 5. Click Apply to display the density contour. 6. On the Animation toolbar, click

to choose the last iteration from the Simulation list.

The resulting contours represent the element densities field resulting from the applied loads and boundary conditions.

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Figure 578:

Viewing an Iso Value Plot of Element Densities An Iso Value plot provides the information about the element density. Iso Value retains all of the elements at and above a certain density threshold. For models with solid design regions, this feature becomes a vital tool for analyzing density results. 1. From the Results toolbar, click

to open the Iso Value panel.

2. Set the Result type to Element Densities. 3. Set Show values to Above. 4. Click Apply. 5. Under Clipped geometry, select Features and Transparent. 6. Change the density threshold. • In the Current value field, enter 0.3.

• Under Current value, move the slider. When you update the density threshold, the Iso value displayed in the modeling window updates interactively. Use this tool to get a better look at the material layout and the load paths from OptiStruct.

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Figure 579:

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OS-T: 2080 Hook with Stress Constraints In this tutorial you will perform a topology optimization on a bracket-hook modeled with shell elements. The objective of this tutorial is to minimize the volume of the material used in the model subject to certain stress constraints. Topology optimization is performed to find the optimal material placement and reduce the volume. This optimization normalizes each element according to its density and lets you remove elements that have low density.

Figure 580: Structural Model with Loads and Constraints

The structural model is loaded into HyperMesh Desktop. The constraints, loads, subcases and material properties are already defined in the model. The topology design variables and the optimization problem setup will be defined using HyperMesh, and OptiStruct is used to determine the optimal material layout. The results can then be reviewed in HyperView. The optimization problem is stated as: Objective Function

Minimize mass.

Constraints

Minimum Member Size = 1.0 Von Mises stress < 1000

Design Variables

The density of each element in the design space.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the hook.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Setting the View 1. In the Model Browser, right-click on Components and select Isolate Only from the context menu. 2. From the Standard Views toolbar, click

to fit the model to the screen.

Only the components display.

Creating Topology Design Variables In this step you will set the optimization to optimize the shell elements in the Design and Base components to create structural members with minimum member size of 1.0 unit in width with thicknesses that vary between zero and the thickness of the shell. The optimization will use 1000 as the maximum stress for any element within the design region when validating the design. 1. From the Analysis page, click optimization.

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2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter shells. 5. Set type: to PSHELL.

6. Using the props selector, select Design and Base. 7. Click create. 8. Update the design variable's parameters. a) Select the parameters subpanel. b) Toggle minmemb off to mindim=, then enter 1.0.

c) Under stress constraint, toggle none to stress= and enter 1000. d) Click update. 9. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the mass response, which is defined for the total volume of the model. a) In the responses= field, enter mass. b) Below response type, select mass.

c) Set regional selection to total and no regionid. d) Click create. 4. Click return to go back to the Optimization panel.

Applying Constraints There is no need for additional constraints, since setting a stress target in the design variable serves as a constraint that limits the amount of material used in the optimized model.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

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Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter frf_response_optimization.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter hook_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file hook_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file. 9. Click Close.

Viewing the Results Viewing the Iso Surface Plot of the Density Results 1. In the HyperWorks Solver View dialog, click Results. The results of the Optimization run and the corresponding Linear Static subcases are loaded into HyperView. 2. Review the Contour plot of element density results. a) From the Results toolbar, click

to open the Contour panel.

b) Set the Result type to Element Densities[s]. c) Click Apply to display the density contour.

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d) In the Results Browser, select Design and Iteration 26 (or your final iteration number).

Figure 581:

3. Review the Iso Value plot of element density results. a) From the Results toolbar, click

to open the Iso Value panel.

b) Set the Result type to Element Densities. c) In the Results Browser, select the last design iteration.

Figure 582:

d) Click Apply.

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e) In the Current value field, change the value to see the results with varying density values. When you update the density threshold, the Iso value displayed in the modeling window updates interactively. Use this tool to get a better look at the material layout and the load paths from OptiStruct.

Figure 583: Iso Value Plot Current value=0.4528

Viewing the Element Stress Results 1. In the top, right of the application, click

to move to the page which displays results from the

Linear Static Analysis of Subcase 1. The results is this page are loaded from hook_opt_s19.h3d, and contain the linear static results for the 1st subcase. 2. From the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Element stresses(2D&3D)(t) and vonMises. 4. In the Results Browser, select the last displayed Iteration. 5. In the Contour panel, click Apply.

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Figure 584: von Mises Stress Results

6. Similarly, review the results from the other subcases. You will notice that there are some local regions where the stresses are still high; this is because topology stress constraints should be interpreted as global stress control or global stress target. The functionality has some ways to filter out the artificial or local stresses caused by point loading or boundary conditions, but those artificial stresses will not be completely removed unless the geometry is changed by shape optimization. Note: There might still be high local stress regions which can be improved more effectively with local shape and size optimization.

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OS-T: 2090 Extrusion Constraints In this tutorial you will use the extrusion constraints method to perform an optimization problem with extrusion constraints to obtain a constant cross section along a given path, particularly in the case of parts manufactured through an extrusion process. By using extrusion manufacturing constraints in topology optimization, constant cross-section designs can be obtained for solid models, regardless of the initial mesh, boundary conditions, or loads. This tutorial show the steps involved in defining topology optimization over a curved beam, simulating a rail, over which a vehicle is moving. Both ends of the beam are supported. A point load is applied over the length of the rail in seven independent load cases, simulating the movement of the vehicle. The rail should be manufactured through extrusion. The steps taken to define the topology design space, the extrusion-manufacturing constraints and the optimization parameters (responses, objective and constraints) using HyperMesh are shown. The DTPL (Design Variable for Topology Optimization) card is used for this optimization. In this tutorial, you will perform topology optimization on a curved beam so that the extruded rail will be stiffer and have less material. The optimization problem is stated as: Objective

Minimize weighted compliance.

Constraints

Volume fraction < 0.3

Design Variables

The density of each element in the design space.

Figure 585: Finite Element Mesh of the Curved Beam with Loads and Boundary Conditions

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears.

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2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the rail_complete.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Creating Topology Design Variables In this step you will create the topology design space definition, design_solid. All elements organized in this design property collector will be included in the design space. 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter design_solid. 5. Set type: to PSOLID.

6. Using the props selector, select new_solid. 7. Click create.

Defining Extrusion Problem and Extrusion Path 1. Display the numbers for nodes 71559 and 70001 in the modeling window. a) From the Display toolbar, click

to open the Numbers panel.

b) Click nodes > by id, then enter 71559,70001 in the id= field. c) Select display.

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d) Click on. e) Click return. 2. Define extrusion path. a) In the topology subpanel, select the extrusion subpanel.. b) Double-click desvar = and select design_solid. c) Switch from none to no twist. Extrusion constraints can be applied to domains characterized by non-twisted cross-sections or twisted cross-sections by using the NOTWIST or TWIST parameters, respectively. d) Click node list > by path, then select node 71559 first and node 70001 second. e) Click update. A line of nodes starting from 71559 and ending with node 70001 should be highlighted, indicating the extrusion path. It is not required to select as many nodes to define the curve. This is an exercise to show that the nodes by path option can also be used. It is necessary to define a 'discrete' extrusion path by entering a series of grids. The curve between these grids is then interpolated using parametric splines. The minimum amount of grids depends on the complexity of the extrusion path. Only two grids are required for a linear path, but it is recommended that at least 5-10 grids be used for more complex curves.

Figure 586: Extrusion Path Definition

3. Click return to go back to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response.

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OptiStruct Tutorials Topology Optimization a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the weighted component response. a) In the responses= field, enter wcomp1.

b) Below response type, select weighted comp. c) Click loadsteps, then select all loadsteps. d) Click return. e) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter constr1. 3. Click response = and select Volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select wcomp1. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rail_complete_extrusion for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog.

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5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Toggle memory options to upper limit in Mb and enter 2000.

8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file rail_complete_extrusion.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Loading Results File and Post-Processing 1. From the OptiStruct panel, click HyperView. 2. In the Results Browser, select the last iteration listed. Iteration 0 is selected by default, which shows your results at the beginning of the optimization. The last iteration shows the final analysis results for this optimization.

Figure 587:

3. From the Results toolbar, click

to open the Iso Value panel.

4. Set the Result type: to Element Densities. 5. Click Apply. 6. In the Current value field, enter 0.3. 7. Click Apply.

The result with manufacturing extrusion constraints permits a constant cross section for the entire length of the model.

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Figure 588: Isosurface plot of a curved beam rail layout of the topology optimization with extrusion constraints

Viewing a Section Cut of the Extrusion Component In the Section Cut panel you can cut planar sections through a model. This is useful when you want to see details inside of a model. 1. On the Display toolbar, click

to open the Section Cut panel.

2. Click Add to create a new section cut. 3. Set Define plane to Y Axis. 4. Using the Base selector, click on any corner at the center of the model. 5. Click Apply. 6. Move the slider under Define plane to scroll though the model. 7. Under Display options, use the slider bar next to Width to change the width of the cross section. The result with manufacturing extrusion constraints shows constant cross section through the length of the model.

Figure 589: Contour Plot of a Section Cut on x-z plane of the curved beam

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OS-T: 2095 Frequency Response Optimization of a Rectangular Plate This tutorial demonstrates the capability of frequency response optimization using OptiStruct. Initially, an existing finite element (FE) model of a flat plate is retrieved and modal frequency response analysis is performed to derive the peak magnitude. A dynamic response optimization is then performed on the same plate to obtain a new design. The new design gives an optimized material layout with a minimized peak response. Post-processing tools will be used in HyperView to visualize iso-plots, magnitude, and phase of the complex displacement results.

Figure 590: Plate Model

The optimization problem is stated as: Objective

Minimize volume.

Constraints

Max FRF Disp. < 600 mm

Design Variables

The density for each element in the design space.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the frf_response_input.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Applying Loads and Boundary Conditions Creating the SPC and Unit Load Collectors The model is constrained at one edge. A unit vertical load will be applied acting upwards in the positive z-direction at a point on a free edge corner of the plate. In this step you will create the two load collectors, spcs and unit-load. 1. Create the spcs load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter spcs.

c) Click Color and select a color from the color palette. d) Set Card Image to None.

Figure 591:

2. Create the unit-load collector.

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a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) For Name, enter unit-load.

c) Click Color and select a color from the color palette. d) Set Card Image to None.

Creating Constraints 1. From the Model Browser, Load Collectors folder, right-click on spc and select Make Current from the context menu.

Figure 592:

2. Display the numbers for nodes 1, 2, 3, and 4 in the modeling window. a) From the Display toolbar, click

to open the Numbers panel.

b) Click nodes > by id, and enter 1,2,3,4 in the id= field. c) Click on.

d) Click return. 3. From the Analysis page, click the constraints panel. 4. Select the create subpanel. 5. Apply constraints to the nodes with IDs 1 and 2. a) Using the nodes selector, select the nodes with IDs 1 and 2. b) Select dof1 - dof6. Dofs with a check will be constrained, while dofs without a check will be free. Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom. Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom. c) Click create. 6. Apply a constraint to the node with ID 4. a) Using the nodes selector, select the node with ID 4. b) Uncheck all dofs except dof3.

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c) Click create. 7. Creating a unit load at a point on the flat plate. a) From the Model Browser, Load Collectors folder, right-click on unit-load and select Make Current from the context menu. b) In the Constraints panel, use the nodes selector to select the node with ID 3. c) Uncheck all dofs except dof3. d) In the dof3= field, enter 20.

e) Click load types= and select DAREA. f) Click create. 8. Click return to go to the main menu.

Figure 593: FE Plate Model with dofs

Creating a Frequency Range Table 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter tabled1.

3. Click Color and select a color from the color palette. 4. Set Card Image to TABLED1. 5. For TABLED1_NUM =, enter 2. 6. Next to Data: x, click

.

7. In the TABLED1_NUM= dialog, define x and y values.

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OptiStruct Tutorials Topology Optimization a) In the y(1) field, enter 1.0.

b) In the x(2) field, enter 1000.0. c) In the y(2) field, enter 1.0.

d) Click Close to exit the dialog.

Figure 594:

A frequency range of 0.0 to 1000.0 with a constant load over this range is created.

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Figure 595:

Creating a Frequency Dependent Dynamic Load 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter rload2.

3. Click Color and select a color from the color palette. 4. Set Card Image to RLOAD2. 5. For EXCITED, click > Loadcol. In the Select Loadcol dialog, select unit-load and click OK. 6. For TB, click > Loadcol. In the Select Loadcol dialog, select tabled1 and click OK. 7. Set TYPE to LOAD. This defines the input as a force.

Creating a Set of Frequencies to be used in the Response Solution 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter freq5.

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3. Click Color and select a color from the color palette. 4. Set Card Image to FREQi. 5. Select FREQ5. 6. In the NUMBER_OF_FREQ5= field, enter 1.

7. In the FREQ5_MAX_NUMBER_OF_FR= field, enter 3. 8. Next to Data: ID, click

.

9. In the NUMBER OF FREQ = dialog, define frequencies values. a) In the F1 field, enter 1.0.

b) In the F2 field, enter 1000.

c) In the FR(0) field, enter 1.0. d) In the FR(1) field, enter 0.8. e) In the FR(2) field, enter 0.2.

f) Click Close to exit the dialog.

Figure 596:

A set of frequencies is defined for the modal method of frequency response analysis by specification of a frequency range and fractions of the natural frequencies within that range.

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Figure 597:

Creating a EIGRL Load Collector 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter eigrl.

3. Click Color and select a color from the color palette. 4. Set Card Image to EIGRL. 5. For ND, enter 17.

This specifies the eigenvalue extraction of the first 17 frequencies using the Lanczos method.

Creating a Load Step 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter subcase1.

3. Set Analysis type to Freq. resp (modal). 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select spcs and click OK. 5. Define METHOD (STRUCT). a) For METHOD (STRUCT), click Unspecified > Loadcol. b) In the Select Loadcol dialog, select eigrl and click OK. 6. Define DLOAD. a) For DLOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select rload2 and click OK. 7. Define FREQ. a) For FREQ, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select freq5 and click OK. 8. Define RESVEC. a) Select RESVEC.

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b) Set TYPE to APPLOAD. c) Set OPTION to YES. An OptiStruct subcase has been created which references the constraints in the load collector spc, the unit load in the load collector rload2; with a set of frequencies defined in load collector freq5 and modal method defined in the load collector eigrl. It is recommended to do a modal analysis before any FRF simulation. Here, this step is suppressed to focus on Frequency Response Analysis setup.

Creating a Set of Nodes for Output of Results 1. In the Model Browser, right-click and select Create > Set from the context menu. A default set displays in the Entity Editor. 2. For Name, enter SETA.

3. Set Card Image to SET_GRID. 4. Set Set Type to non-ordered. 5. For Entity IDs, click 0 Nodes > Nodes. 6. Using the nodes selector, select the nodes with the ID of 3. This is the node where the load was applied. 7. In the panel area, click proceed. With FRF simulation, the amount of data generated can easily create big results files. It is a good practice to work with sets where you can specify only the points of interest. This reduces the CPU time and the amount of data to be saved.

Creating a Set of Outputs and Include Damping for Frequency Response Analysis 1. From the Analysis page, click the control cards panel. The Card Image dialog opens. 2. Define GLOBAL_OUTPUT_REQUEST. a) Click GLOBAL_OUTPUT_REQUEST. b) Select DISPLACEMENTS. A new set of options appears in the work area screen. c) Click FORM(1) and select PHASE. d) Click OPTION(1) and select SID. A new field, SID(1) appears in yellow. e) Double-click SID(1) and select SETA. A value of 1 now appears below the SID field box. This sets the output for only the nodes in set 1.

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Figure 598:

f) Click return to exit GLOBAL_OUTPUT_REQUEST. 3. Define FORMAT. a) Click FORMAT. b) In the number_of_formats= field, enter 2.

c) Under FORMAT_V1, click the second instance of FORMAT and select OPTI. d) Click return. 4. Define PARAM. a) Click PARAM. b) Select G. c) Click G_V1 and enter 0.05.

This specifies that the system will have a constant damping coefficient equal to 2.5% of the Critical Damping Ratio.

d) Click return. 5. Define OUTPUT. a) Click OUTPUT. b) Set KEYWORD to HGFREQ. c) Set FREQ to LAST. d) Leave number_of_outputs= set to 1. e) Click return. 6. Click return to return to the main menu.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter frf_response_input.hm for the file name and save it to your working directory.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

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Figure 599: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter frf_response_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Clear the options field. 9. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the frf_response_analysis.fem was written. The frf_response_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results In this step you will view displacement results (.mvw file) in HyperGraph, and you will vview the displacement output (.disp file) from this run. The results file (.h3d) contains only the displacement results for the three nodes specified in the node set output. 1. In the OptiStruct panel, click HyperView to load the results from the analysis into the next page. 2. From the menu bar, click File > Open > Session. 3. In the Open Session File dialog, navigate to the directory where the job was run and open the frf_response_analysis_freq.mvw file.

a) Optional: If you launched from the OptiStruct panel, click Yes to discard the current session.

Two graphs are displayed. The graph title shows Subcase 1(subcase1)-Displacements of grid 3. The top graph shows Phase Angle verses Frequency. The bottom graph shows Displacement Response verses Frequency.

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Figure 600:

4. From the Curves toolbar, click

to open the Define Curves panel.

5. Delete the X Trans and Y Trans curves. The excitation is applied on Z direction then, the main effect will be detected on this direction. 6. On the Results toolbar, click

to open the Curve Attributes panel.

7. Change the line attribute to continue

.

8. Click the Symbol Attributes tab, and select the square symbol.

Figure 601:

9. From the Annotations toolbar, click 10. Change the Axis to Vertical.

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Figure 602:

11. Click the Scale and Tics (Magnitude) tab, and select Logarithmic. 12. In the Min field, enter 5.

13. In the Max field, enter 200000.

14. Click the Scale and Tics (Phase) tab, and change the Tics per axis to 7. 15. Set the Axis to Horizontal.

Figure 603:

16. In the Min field, enter 5.

17. In the Max field, enter 1000.

Figure 604: Frequency Response Function FRF (Node 3, Z-Displacement)

18. From the Curves toolbar, click

to open the Coordinate Info panel.

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19. Under Find point, select Magnitude.

Figure 605:

20. Click the maximum button to see the maximum Y-magnitude ~ 15055 in the table. The peak displacement of the baseline model.

Figure 606:

21. Return to HyperMesh by changing the client selector to

.

Opening the Model 1. Click File > Open > Model. 2. Select the frf_response_input.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The frf_response_input.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter frf_response_optimization.hm for the file name and save it to your working directory.

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Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter plate. 5. Set type: to PSHELL.

6. Using the props selector, select Design. 7. For base thickness, enter 0.15. 8. Click create.

A topology design space definition, shield, has been created. All elements referring to the design property collector (elements organized into the "design" component collector) are now included in the topology design space. The thickness of these shells can vary between 0.15 (base thickness) and the maximum thickness defined by the T (thickness) field on the PSHELL card. The object of this exercise is to determine where to locate ribs in the designable region. Therefore, a non-zero base thickness is defined, which is the original thickness of the shells. The maximum thickness, which is defined by the T field on the PSHELL card, should be the allowable depth of the rib. Currently, the T field on the PSHELL card is still set to 0.15 (the original shell thickness). You will change this to a higher value to create a design space where the material can be removed. 9. Update the design variable's parameters. a) Select the parameters subpanel. b) Toggle minmemb off to mindim=, then enter 2.0.

c) Toggle maxmemb off to maxdim=, then enter 6.0. d) Click update. 10. Click return. 11. Edit the thickness of the design property. a) In the Model Browser, Properties folder, click design. b) In the Entity Editor, T field, enter 1.000.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter volume. b) Below response type, select volume.

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c) Set regional selection to total and no regionid. d) Click create. 4. Create the frequency response displacement (constraint), which defines the maximum magnitude on dof3. a) In the responses= field, enter frfdisp.

b) Set the response type to frf displacement. c) Switch the component from real to magnitude. d) Set the function to all freq. e) Using the nodes selector, select the node with ID 3. f) Select dof3. g) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter constr. 3. Click response = and select frfdisp.

4. Check the box next to upper bound, then enter 600. 5. Using the loadsteps selector, select subcase1. 6. Click create. 7. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter frf_response_optimization for filename. For OptiStruct input decks, .fem is the recommended extension.

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4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file frf_response_optimization.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: frf_response_optimization.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. frf_response_optimization.HM.comp.tcl HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. frf_response_optimization.HM.ent.tcl HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs. frf_response_optimization.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. frf_response_optimization.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. frf_response_optimization.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the frf_response_optimization.fem file. frf_response_optimization.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. frf_response_optimization.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on.

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frf_response_optimization_des.h3d HyperView binary results file that contain optimization results. frf_response_optimization_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. frf_response_optimization.his_data The OptiStruct history file containing iteration number, objective function values and percent of constraint violation for each iteration.

Viewing the Results Element Density and Element Thickness results are output from OptiStruct for all iterations.

Viewing a Static Plot of the Density Results 1. From the OptiStruct panel, click HyperView. 2. Open the frf_response_optimization.mvw session file. a) From the menu bar, click File > Open > Session.

b) In the Open Session File dialog, navigate to your working directory and open the frf_response_optimization.mvw session file.

3. From the Results toolbar, click

to open the Contour panel.

4. In the Results Browser, select the last load case simulation.

Figure 607:

5. In the Contour panel, set the averaging method to simple. 6. Click apply. Each element of the model is assigned a legend color, indicating the density of each element for the selected iteration. The last design iteration gives the optimized material layout.

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Figure 608: Contour of the Baseline Model The final design iteration is displayed

Comparing the Peak Displacement of the Optimization Run 1. Open the FRF_response_analysis_freq.mvw session file. a) From the menu bar, click File > Open > Session.

b) In the Open Session File dialog, navigate to your working directory and open the FRF_response_analysis_freq.mvw session file.

2. On the Curves toolbar, click

to open the Build Plots panel, which you will use to add curves on

top of the existing analysis information. 3. In the Data file field, load the frf_response_optimization_s2.h3d optimization file, which contains the final iteration analysis.

Figure 609:

4. Set Subcase to the last iteration.

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OptiStruct Tutorials Topology Optimization 5. Set X Type to Frequency. 6. For Y Type, select Displacement (Grids). 7. For Y Request, select N3. 8. For Y Component, select X, Y, and Z. 9. Click Apply to overlay the new information onto the original plot.

Figure 610: Original and Final Design Results for the Plate

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OS-T: 2098 Excavator Arm In this tutorial you will set up an optimization problem of an MBD system using the equivalent static load method (ESL). You will setup the model in HyperMesh, and run the Topology optimization job with OptiStruct. The Objective of the optimization is to maximize the stiffness of the Lower arm of an excavator model, while keeping the mass to less than an allowable value. The model units are kg, N, m and s.

Figure 611: Excavator Model

The optimization problem for this tutorial is stated as: Objective

Minimize the maximum compliance in an ESL loadstep.

Constraints

Upper bound on volume fraction.

Design Variables

Element density of elements in the lower arm (flexible body) component.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears.

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2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the Excavator_MBD.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Excavator_MBD.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Submitting the Job The model already has the excavator MBD analysis set up with all the bodies defined as rigid bodies.. 1. From the Analysis page, click the OptiStruct panel.

Figure 612: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter excavator_MBD_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Clear the options field.

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9. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the excavator_MBD_analysis.fem was written. The excavator_MBD_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results 1. When the message ANALYSIS COMPLETED is received in the dialog, close the dialog. 2. From the OptiStruct panel, click HyperView. The results for the current run automatically load into HyperView. 3. From the Animation toolbar, click 4. On the Page Controls toolbar, click

to start the animation and review the MBD model. to delete the page, close HyperView, and return to

HyperMesh.

Setting Up the Optimization Changing the Rigid Body into a Flexible Body In this step you define the topology optimization on the body, Lower_Arm. It was originally modeled as a rigid body and needs to be converted to a flexible body for the optimization. 1. From the Analysis page, click the bodies panel. 2. Select the update subpanel. 3. Double-click body= and select Lower_Arm. 4. Click review. The lower arm component is highlighted. Body type PRBODY is shown for type=, indicating that lower arm is modeled as a rigid body. You will update this body to a flexible body type, and also define topology optimization on this body. 5. Click type= and select PFBODY. 6. In the nmodes= field, enter 20.

This increases the number of modes included in the CMS method to 20.

Figure 613: Updating Body Type for Lower_Arm

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7. Click update. A message appears in the lower left corner to indicate that the body has been update to a new type. 8. Click return.

Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter L_Arm_Topology. 5. Set type: to PSOLID.

6. Using the props selector, select lowerarm. 7. Click create. 8. Update the design variable's parameters. a) Select the parameters subpanel. b) Toggle minmemb off to mindim=, then enter 0.05. c) Click update. 9. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to by entity and no regionid. d) Using the props selector, select lowerarm. e) Click create. 4. Create the compliance response. a) In the response= field, enter Comp.

b) Below response type, select compliance. c) Set regional selection to total and no regionid. d) Click create. 5. Click return to go back to the Optimization panel.

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Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter Vol_Constr. 3. Click response = and select Volfrac.

4. Check the box next to upper bound, then enter 0.5. 5. Click create.

6. Click return to go back to the Optimization panel. A constraint is defined on the response Volfrac. The constraint will force the volume fraction used in the design space to be less than 0.5.

Defining the Objective Reference 1. From the Analysis page, Optimization panel, click the obj reference panel. 2. In the dobjref= field, enter MAX_Compin. 3. Select pos reference, and enter 1.0.

4. Select neg reference, and enter -1.0. 5. Click response and select Comp.

6. Set the loadsteps selection option to all. This ensures the design objective reference includes compliances from all the load steps that are calculated by the ESL method. 7. Click create. 8. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that minmax is selected. 3. Click dobjrefs and select MAX_Comp. 4. Click create. 5. Click return twice to exit the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter excavator_MBD_Topology.hm for the file name and save it to your working directory.

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Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter excavator_MBD_Topology for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file excavator_MBD_Topology.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results 1. When the message OPTIMIZATION HAS CONVERGED is received in the command window, close the DOS window. 2. From the OptiStruct panel, click HyperView. The results are load into HyperView. 3. In the Results Browser, select the final Outerloop iteration to load the optimized topology results.

Figure 614:

4. From the Results toolbar, click

to open the Iso Value panel.

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5. Set the Result type to Element densities (s). 6. Click Apply. Only the elements that have elemental density higher than what is shown Current value field display.

Figure 615:

7. Change the density threshold. • In the Current value field, enter 0.5.

• Under Current value, move the slider. 8. Set Show values to Above. 9. In the Model Browser, Component folder, right-click on Lower_Arm and select Isolate from the context menu. 10. In the Iso Value panel, under Clipped geometry, select Features to visualize the complete design space.

Figure 616:

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Topography Optimization Topography Optimization

This chapter covers the following: •

OS-T: 3000 Topography Optimization of a Plate Under Torsion (p. 659)

•

OS-T: 3010 Topography Optimization of an L-bracket (p. 670)

•

OS-T: 3020 Automatic Recognization of Bead Results of an L-Bracket (p. 678)

•

OS-T: 3030 Random Response Optimization (p. 684)

10

OptiStruct Tutorials Topography Optimization

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OS-T: 3000 Topography Optimization of a Plate Under Torsion In this tutorial you will perform a topography optimization of a plate under torsion. You will use a finite element model of the design space with loads and constraints in this tutorial. It is assumed that the part is to be formed using a stamping process. The objective is to minimize the displacement of the node where the force is applied in the positive z-direction. Only the shape of the plate can be changed to achieve the objective, not the thickness.

Figure 617: Finite Element Model of the Design Space with Loads and Constraints

A finite element model is loaded into HyperMesh. The constraints, load, material properties, and subcase (loadstep) of the model are already defined. Topography design variables and optimization parameters are defined and the OptiStruct software determines the optimal reinforcement patterns. The results are viewed as animations of the contours of shape changes of the design space. Finally, the use of the grouping patterns is shown; based on the shape changes suggested by OptiStruct, a possible pattern is chosen for ease of manufacturing. The optimization problem for this tutorial is stated as: Objective

Minimize nodal displacement at grid point where loading is applied.

Design Variables

Shape variables generated automatically on the designable space aligned with the elements normal.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the torsion_plate.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The torsion_plate.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Verifying the Thickness of the Component 1. In the Model Browser, Properties folder, click design. The design property opens in the Entity Editor, which displays information regarding shell thicknesses on the PSHELL card. 2. Verify that the thickness, T, is set to 1.0.

Setting Up the Optimization Defining Topography Design Variables For a topography optimization, a design space and a bead definition need to be defined. 1. From the Analysis page, click the optimization panel. 2. Click the topography panel. 3. Create a topography design space definition. a) Select the create subpanel. b) In the desvar= field, enter topo.

c) Using the props selector, select design. d) Click create.

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A topography design space definition, topo, has been created. All elements organized into the design component collector(s) are now included in the design space. 4. Create a bead definition for the design space topo. a) Select the bead params subpanel. b) Verify the desvar = field is set to topo, which is the name of the newly created design space. c) In the minimum width= field, enter 5.0.

This parameter controls the width of the beads in the model. The recommended value is between 1.5 and 2.5 times the average element width.

d) In the draw angle= field, enter 60.0 (this is the default).

This parameter controls the angle of the sides of the beads. The recommended value is between 60 and 75 degrees.

e) In the draw height=, enter 4.0.

This parameter sets the maximum height of the beads to be drawn.

f) Select buffer zone. This parameter establishes a buffer zone between elements in the design domain and elements outside the design domain. g) Toggle draw direction to normal to elements. This parameter defines the direction in which the shape variables are created. h) Set boundary skip to load and spc. This tells OptiStruct to leave nodes at which loads or constraints are applied out of the design space. i) Click update. A bead definition has been created for the design space topo. Based on this information, OptiStruct will automatically generate bead variable definitions throughout the design variable domain. 5. Update the bounds of the design variable. a) Select the bounds subpanel. b) Verify the desvar = field is set to topo, which is the name of the design space. c) In the Upper Bound= field, enter 1.0.

Upper bound on variables controlling grid movement (Real > LB, default = 1.0). This sets the upper bound on grid movement equal to UB*HGT.

d) In the Lower Bound= field, enter 0.0. e) Click update.

The upper bound sets the upper bound on grid movement equal to UB*HGT and the lower bound sets the lower bound on grid movement equal to LB*HGT. 6. Click return to go to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization.

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2. Click Responses. 3. Create the displacement response. a) In the response= field, enter displace.

b) Below response type, select static displacement. c) Click nodes > by id, then enter 2500 in the id= field. d) Set the displacement type to dof3. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

e) Click create. 4. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select displace. 4. Using the loadsteps selector, select torsion. 5. Click create. 6. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter torsion_plate for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization.

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The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file torsion_plate.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: torsion_plate.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. torsion_plate.hist The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history. torsion_plate.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. torsion_plate.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. torsion_plate.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the torsion_plate.fem file. torsion_plate.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. torsion_plate.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. torsion_plate_des.h3d HyperView binary results file that contain optimization results. torsion_plate_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. torsion_plate.grid An OptiStruct file where the perturbed grid data is written.

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Viewing the Results Shape contour information is output from OptiStruct for all iterations. In addition, Displacement and Stress results are output for the first and last iteration by default. This section describes how to view those results using HyperView.

Viewing a Static Plot of Shape Contours 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads the torsion_plate_des.h3d and torsion_plate_s1.h3d files reading the model and optimization results. 2. On the Results toolbar, click

to open the Contour panel.

3. Set Result type to Shape Change (v) and Mag.

Figure 618:

4. On the Animation toolbar, click A deformed plate appears.

to choose the last iteration from the Simulation list.

5. Click Apply. Is the max= field showing 4.0e + 00? In this case, it is. If it is not, your optimization has not progressed far enough. Decrease the OBJTOL parameter (set in the opti control panel on the optimization panel). This value, 4.0e+00, comes from the draw height defined earlier.

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Figure 619: Contour Plot showing the reinforcement pattern at the last iteration (converged solution)

Viewing a Transient Animation of the Shape Contour Changes A transient animation of contour shapes will give a good idea of the shape changes happening through different iteration. 1. From the Animation toolbar, set the animation mode to

(Transient).

Figure 620:

2. Click

to start the animation.

3. Click

to open the Animation Controls panel.

4. With the animation running, use the slider bar, below Max Frame Rate, to adjust the speed of the animation. 5. Click

to pause the animation.

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Viewing the Deformed Structure The displacement and stress results from the first and last iterations (default) are given in the torsion_plate_s1.h3d file. 1. In the top, right of the application, click

to go to the next page.

This page has the subcase information from the torsion_plate_s1.h3d file.

2. On the Animation toolbar, set the animation mode to Linear Static.

Tip: For a better visual of what it happening with this model, turn on mesh lines and contour the results. 3. On the Results toolbar, click

to open the Deformed panel.

4. Set the Result type to Displacement(v). 5. In the Results Browser, select the first iteration (Iteration 0).

Figure 621:

6. On the Animation toolbar, set the animation mode to 7. Click

to start the animation.

8. Click

to go to the Animation Controls panel.

(Linear Static).

9. With the animation running, use the slider bar, below Max Frame Rate, to adjust the speed of the animation. A deformation animation of the original model is shown. Does the deformed shape look correct for the boundary conditions you applied to the mesh? 10. Click

to stop the animation.

11. On the Page Controls toolbar, click

to delete the HyperView page.

Adding Pattern Grouping Constraints Pattern grouping will be added as a constraint for manufacturability.

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The configuration obtained in the previous example (see the contour plot showing the reinforcement pattern at the 17th iteration) might be difficult to manufacture. It does give an idea of what kinds of patterns are likely to optimize the structure (in this case -- to minimize the displacement at the selected node). A possible pattern, suggested by the static contour plot obtained in the previous exercise, is to use channels parallel to a diagonal. In this example, you choose the diagonal emerging from the node where the load is applied. 1. In HyperMesh, click return to exit the OptiStruct panel. 2. From the Analysis page, click the optimization panel. 3. Click the topography panel. 4. Select the pattern grouping subpanel. 5. Click desvar = and select topo. 6. Set the pattern type to linear. 7. Set the sub-type to basic. 8. Select nodes. a) Using the anchor node selector, select the node at the corner where the load is applied. HyperMesh automatically moves the blue halo around the first node. b) Using the first node selector, select the node in the opposite corner.

Figure 622: Pattern Grouping Node Location

9. Click update. 10. Click return twice to go to the main menu.

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Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter torsion_pattern for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file torsion_pattern.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

View the new results as before. Also check the objective value for the zero-th and last iteration in the .out file. How does the final value for the objective compare to the final value obtained using 'none' option for pattern grouping?

Viewing a Static Plot of Shape Contours Repeat the steps in the previous steps to view the contour plot of the shape change.

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Figure 623: Contour Plot Showing the Reinforcement Pattern with pattern grouping constraint at the last iteration.

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OptiStruct Tutorials Topography Optimization

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OS-T: 3010 Topography Optimization of an Lbracket In this tutorial you will perform a topography optimization on a L-bracket modeled with an attached mass. The bracket is modeled with shell elements. The objective is to maximize the frequency of the first mode by introducing beads or swages to the bracket. This can be achieved by using topography optimization. The regions around the holes are specified as non-designable, while the bulk of the bracket is available for developing stiffening beads.

Figure 624: L-bracket Layout

The optimization problem for this tutorial is stated as: Objective

Maximize 1st frequency mode.

Constraints

Bead dimensions and layout.

Design Variables

Perturbation of nodes normal to the shell's mid-plane.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the Lbkttopog.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Lbkttopog.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Defining Topography Design Variables For a topography optimization, a design space and a bead definition need to be defined. In this step, the values of a bead width of 15mm, a bead height of 5mm, and draw angle of 85 degrees will be used. Symmetry of the bead pattern should be forced along the symmetry line of the design space. 1. From the Analysis page, click the optimization panel. 2. Click the topography panel. 3. Create a topography design space definition. a) Select the create subpanel. b) In the desvar= field, enter topo.

c) Using the props selector, select design. d) Click create. A topography design space definition, topo, has been created. All elements organized into the design component collector(s) are now included in the design space. 4. Create a bead definition for the design space topo. a) Select the bead params subpanel.

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b) Verify the desvar = field is set to topo, which is the name of the newly created design space. c) In the minimum width= field, enter 15.0.

This parameter controls the width of the beads in the model. The recommended value is between 1.5 and 2.5 times the average element width.

d) In the draw angle= field, enter 85.0 (this is the default).

This parameter controls the angle of the sides of the beads. The recommended value is between 60 and 75 degrees.

e) In the draw height=, enter 5.0.

This parameter sets the maximum height of the beads to be drawn.

f) Select buffer zone. This parameter establishes a buffer zone between elements in the design domain and elements outside the design domain. g) Toggle draw direction to normal to elements. This parameter defines the direction in which the shape variables are created. h) Set boundary skip to load and spc. This tells OptiStruct to leave nodes at which loads or constraints are applied out of the design space. i) Click update. A bead definition has been created for the design space topo. Based on this information, OptiStruct will automatically generate bead variable definitions throughout the design variable domain. 5. Adding pattern grouping constraints. a) Select the pattern grouping subpanel. b) Click desvar = and select topo. c) Set the pattern type to 1-pln sym. d) Click anchor node, and enter 337 in the id= field. e) Click first node, and enter 613 in the id= field. f) Click update.

6. Update the bounds of the design variable. a) Select the bounds subpanel. b) Verify the desvar = field is set to topo, which is the name of the design space. c) In the Upper Bound= field, enter 1.0.

Upper bound on variables controlling grid movement (Real > LB, default = 1.0). This sets the upper bound on grid movement equal to UB*HGT.

d) In the Lower Bound= field, enter 0.0. e) Click update.

The upper bound sets the upper bound on grid movement equal to UB*HGT and the lower bound sets the lower bound on grid movement equal to LB*HGT. 7. Click return to go to the Optimization panel.

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Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the frequency response. a) In the responses= field, enter FREQ.

b) Below response type, select frequency. c) For Mode Number, enter 1.0. d) Click create.

A response, FREQ, is defined for the frequency of the first mode extracted. 4. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that max is selected. 3. Click response and select FREQ. 4. Using the loadsteps selector, select STEP. 5. Click create. 6. Click return twice to exit the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter Lbkttopog.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Lbkttopog for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file Lbkttopog.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: Lbkttopog.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. Lbkttopog.hist The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history. Lbkttopog.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. Lbkttopog.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. Lbkttopog.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the Lbkttopog.fem file. Lbkttopog.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. Lbkttopog.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. Lbkttopog_des.h3d HyperView binary results file that contain optimization results. Lbkttopog_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. Lbkttopog.grid An OptiStruct file where the perturbed grid data is written.

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Viewing the Results Shape contour information is output from OptiStruct for all iterations. In addition, Eigenvector results are output for the first and last iteration by default. This section describes how to view those results in HyperView.

Viewing a Transient Animation of Shape Contour Changes 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads the Lbkttopog_des.h3d file. 2. On the Animation toolbar, set the animation mode to Transient.

Figure 625:

3. Click

to start the animation.

4. Click

to open the Animation Controls panel.

5. Move the Max Frame Rate slider to adjust the animation speed.

Reviewing the Optimized Frequency Difference 1. In the top, right of the application, click

to proceed page 3, which contains the results for first

and the last iterations. 2. In the Results Browser, select the first iteration (Iteration 0). The frequencies of all of the modes requested from the analysis are shown in the Subcase drop-down.

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Figure 626: Frequency of the First Mode for Iteration 0

Look at the frequency values for the last iteration. Upon observation, the frequency for the first mode has changed from around 48 Hz to around 93 Hz for first and last iterations, respectively.

Figure 627: Frequency of the First Mode for Iteration 12

Applying Optimized Topography 1. In the top, right of the application, click 2. On the Animation toolbar, click

to go back to the Design History page (page 2).

to set the Current time to the last step.

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Figure 628: Topography Results

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OS-T: 3020 Automatic Recognization of Bead Results of an L-Bracket In this tutorial you will run the completed model from OS-T: 3010 Topography Optimization of an Lbracket, post-process the results, and use the autobead functionality. The objective of autobead is to offer automation of bead interpretation so that a prototype-like design could be created automatically.

Figure 629: L-bracket Layout

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the Lbkttopog_bead.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Lbkttopog_bead for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file Lbkttopog_bead.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Shape contour information is output from OptiStruct for all iterations. In addition, Eigenvector results are output for the first and last iteration by default. This section describes how to view those results in HyperView.

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Reviewing a Transient Animation of Shape Contour Changes 1. From the OptiStruct panel, click HyperView. 2. Load the results session. a) From the menu bar, click File > Open > Session. b) In the Open Session File dialog, navigate to your working directory and open the Lbkttopog_bead.mvw file.

3. On the Animation toolbar, set the animation mode to 4. Click

(Transient).

to start the animation.

The animation shows how the shape changes over the course of the optimization. 5. To slow down the animation, move the animation controls slider under the Current Frame Indicator and adjust the Max Frame Rate slider.

Figure 630:

Reviewing the Optimized Frequency Difference 1. In the top, right of the application, click

to proceed to the next page.

2. On the Animation toolbar, set the animation mode to

(Modal).

3. In the Results Browser, from the list of load cases, toggle between Iteration 0 and Iteration 12.

Figure 631:

The topography optimization yields an almost 100% increase in the frequency of the first mode by reviewing the Mode 1-F value in the Simulation list. 4. Click

to animate the model.

Generating a New Model Based on a Topography Result Applying Optimized Topography 1. Go back to HyperMesh.

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2. Click return to exit the OptiStruct panel. 3. From the Post page, click the apply results panel. 4. Click simulation = and select DESIGN - ITER 12. 5. Click data type = and select Shape Change. 6. Select displacements. 7. Set component selection to total disp. 8. Click nodes > all. 9. In the mult = field, enter 1.0.

10. Click apply. The final nodal positions are applied to the structure. Tip: Be careful with saving the model now, the HyperMesh database has changed. This model can be used for further analyses. Results can now be viewed on the final shape. 11. Click reject to get back the original shape. 12. Click return to go back to main menu.

Importing Final Geometry using OSSmooth and Autobead 1. From the Post page, click the OSSmooth panel.

Figure 632:

2. In the file: field, select the OptiStruct base input file from which to extract the final geometry. 3. In the output: field, select the IGES output format of the final geometry. • The default output format is STL. Other format options are: Mview, Nastran, IGES, and H3D. • If you select IGES as the output format, select the output unit type. The default is mm (millimeters). 4. Select load geom to load the new geometry into the current HyperMesh session. 5. Select autobead, and enter 0.3 for the bead threshold. 6. Leave the rest of the options at their default settings. 7. Click OSSmooth. 8. Click Yes to overwrite. The new geometry will be automatically loaded into the existing HyperMesh file, turn off the display of all the elements to view the new concept geometry. OSSmooth can automatically create geometry based on the new mesh.

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9. Click FE > Surf to generate new geometry from the optimization results. 10. Click Save and Exit to continue. 11. In the Mask browser, click Isolate for Geometry and click Hide for Load Collectors.

Figure 633:

12. In the Model Browser, uncheck geometry display for the original components design and fixed.

Figure 634:

New geometry for the optimized part is displayed.

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Figure 635:

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OS-T: 3030 Random Response Optimization In this tutorial you will perform a topography optimization with random response on a flat plate. A random response analysis has been set up. The flat panel is constrained through an RBE2 element. Two frequency-varying accelerations are applied on the independent node of the RBE2 element as excitations. They are correlated through a cross-spectral density. The objective of the optimization is to minimize the maximum (minmax) Power Spectral Density (PSD) acceleration in X direction at the center of the panel.

Figure 636: Model Review

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck.

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An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the panel.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Defining Topography Design Variables For a topography optimization, a design space and a bead definition need to be defined. In this step, the design space is composed of the shell elements with the property PSHELL_5. A minimum bead width of 0.4, a bead height of 1, and draw angle of 60 degrees is used in the bead definition. A 2-plane symmetrical pattern grouping constraint is defined to generate a symmetrical bead design. 1. From the Analysis page, click the optimization panel. 2. Click the topography panel. 3. Create a topography design space definition. a) Select the create subpanel. b) In the desvar= field, enter plate.

c) Using the props selector, select PSHELL_5. d) Click create. A topography design space definition, plate, has been created. All elements organized into the PSHELL_5 component collector(s) are now included in the design space. 4. Create a bead definition for the design space plate. a) Select the bead params subpanel. b) Verify the desvar = field is set to plate, which is the name of the newly created design space. c) In the minimum width= field, enter 0.4.

This parameter controls the width of the beads in the model. The recommended value is between 1.5 and 2.5 times the average element width.

d) In the draw angle= field, enter 60.0 (this is the default).

This parameter controls the angle of the sides of the beads. The recommended value is between 60 and 75 degrees.

e) In the draw height=, enter 1.0.

This parameter sets the maximum height of the beads to be drawn.

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f) Select buffer zone. This parameter establishes a buffer zone between elements in the design domain and elements outside the design domain. g) Toggle draw direction to normal to elements. This parameter defines the direction in which the shape variables are created. h) Set boundary skip to none. This tells OptiStruct to leave nodes at which loads or constraints are applied out of the design space. i) Click update. A bead definition has been created for the design space plate. Based on this information, OptiStruct will automatically generate bead variable definitions throughout the design variable domain. 5. Adding pattern grouping constraints. a) Select the pattern grouping subpanel. b) Click desvar = and select plate. c) Set the pattern type to 2-plns sym. d) Set the anchor node, first node, and second node selectors to coordinates, then enter the values indicated in Figure 637 to define a 2-plane symmetry constraint.

Figure 637:

e) Click update. 6. Update the bounds of the design variable. a) Select the bounds subpanel. b) Verify the desvar = field is set to plate, which is the name of the design space. c) In the Upper Bound= field, enter 1.0.

Upper bound on variables controlling grid movement (Real > LB, default = 1.0). This sets the upper bound on grid movement equal to UB*HGT.

d) In the Lower Bound= field, enter -1.0. e) Click update.

The upper bound sets the upper bound on grid movement equal to UB*HGT and the lower bound sets the lower bound on grid movement equal to LB*HGT. 7. Click return to go to the Optimization panel.

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Creating Design Response for Random Response Optimization The PSD acceleration in X direction at the center of the plate is defined as design response for the random response optimization. 1. Click the responses panel. 2. In the response = field, enter psdaccl.

3. Set the response type to psd acceleration. 4. Click nodes > by id, then enter 67 in the id= field. Node 67 is close to the center of the plate.

5. Select dof1 for the PSD acceleration in X direction. 6. Click randps= and select RANDPS100. This specifies the Power Spectral Density for the random response analysis. 7. Leave frequencys set to all freq. 8. Set the region to no regionid. 9. Click create. 10. Click return to go back to Optimization Setup panel.

Defining the Objective Reference 1. From the Analysis page, Optimization panel, click the obj reference panel. 2. In the dobjref= field, enter psdacclref.

3. Select pos reference, and enter 1.0e6.

The values of the response, psdaccl, will be normalized by the negative and positive reference values.

4. Select neg reference, and enter -1.0. 5. Click response and select psdaccl.

6. Set the loadsteps selection option to all. This ensures the DOBJREF entry is applied to all subcases.

7. Click create.

8. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that minmax is selected. 3. Click dobjrefs and select psdacclref. 4. Click create. 5. Click return twice to exit the Optimization panel.

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Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter panel_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file panel_complete.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results HyperView is used to view the bead design generated from the topography optimization. “XYPUNCH, ACCE, PSDF/67(T1RM)” was used to output the PSD accelerations to punch files. The PSD plot from punch output can be viewed with HyperGraph. The RMS and peak PSD values are output to the .peak file and can be viewed with text editor.

Viewing the Bead Patterns 1. From the OptiStruct panel, click HyperView. HyperView is launched and the optimization results (_des.h3d) are loaded. 2. On the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Shape Change (v). 4. In the Results Browser, select the last iteration. 5. In the Contour panel, click Apply. The shape change contour displays.

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Figure 638: Results of Random Response Optimization

Viewing the PSD Results 1. Launch HyperGraph. 2. On the Curves toolbar, click

to open the Build Plots panel.

3. Load the panel_complete.pch file.

4. Set the X Type to Frequency (Hz). 5. Set Group 1 Acceleration to Y Type. Node id 67 and X_Translation are highlighted. 6. Click Apply. The PSD plot of acceleration in X direction on node 67 at iteration 0 is loaded. 7. On the Annotations toolbar, click

to open the Axes panel and convert the linear plot of PSD

acceleration to logarithmic plot for the y-axis. 8. Select the last group acceleration as Y Type. 9. Click Apply. 10. On the Annotations toolbar, click

to open the Axes panel and convert the linear plot of PSD

acceleration to logarithmic plot for the y-axis.

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OptiStruct Tutorials Topography Optimization The PSD plot of acceleration in X direction on node 67 at final iteration is loaded. How much was the peak value of the PSD acceleration reduced?

Figure 639: PSD Acceleration Plots of the Original and the Optimized Designs

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Combination Optimization

11

Combination Optimization

This chapter covers the following: •

OS-T: 3100 Combined Topology and Topography Optimization of a Slider Suspension (p. 692)

•

OS-T: 3200 Design of a Composite Aircraft Underbelly Fairing (p. 700)

•

OS-T: 3300 Lattice Optimization Process (p. 726)

•

OS-T: 3400 Design an Open Hole Tension (OHT) (p. 741)

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OS-T: 3100 Combined Topology and Topography Optimization of a Slider Suspension In this tutorial you will perform a combined topology and topography optimization on a slider suspension using OptiStruct. The objective of this tutorial is to increase the stiffness of the slider suspension and make it lighter at the same time. This requires the use of both topology and topography optimization. The finite element model of the slider suspension contains force and boundary conditions. The structure is made of quad elements and has both linear statics and normal modes subcases (loadsteps). Steps are described to define topology and topography design space, responses, constraints, and objective function. The optimized structure will be stiffer for both linear statics and normal modes subcases and will have beads and less material.

Figure 640: Disk Drive Slider

Problem Statement Perform combined topology and topography optimization on a disk drive slider suspension to maximize the stiffness and weighted mode. The lower bound constraint on the seventh mode is 12 cycles/ms. Objective Function

Minimize the combined weighted compliance and the weighted modes.

Constraints

7

Design Variables

Element densities and nodes topography.

th

Mode > 12 cycles/ms.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the combined.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Creating Topology Design Variables 1. From the Analysis page, click optimization. 2. Click topology. 3. Select the create subpanel. 4. In the desvar= field, enter pin. 5. Set type: to PSHELL.

6. Using the props selector, select 1pin. 7. Verify that the base thickness is 0.0. A value of 0.0 implies that the thickness at a specific element can go to zero, and therefore becomes a void. 8. Click create. 9. Repeat the above steps to create a design variable labeled bend, and assign it the 3bend property. 10. Click return.

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Defining Topography Design Variables For a topography optimization, a design space and a bead definition need to be defined. 1. From the Analysis page, click the optimization panel. 2. Click the topography panel. 3. Create a topography design space definition. a) Select the create subpanel. b) In the desvar= field, enter tpg.

c) Using the props selector, select 1pin and 3bend. d) Click create. A topography design space definition, tpg, has been created. All elements organized into the 1pin and 3bend component collector(s) are now included in the design space. 4. Create a bead definition for the design space tpg. a) Select the bead params subpanel. b) Verify the desvar = field is set to tpg, which is the name of the newly created design space. c) In the minimum width= field, enter 0.4.

This parameter controls the width of the beads in the model. The recommended value is between 1.5 and 2.5 times the average element width.

d) In the draw angle= field, enter 60.0 (this is the default).

This parameter controls the angle of the sides of the beads. The recommended value is between 60 and 75 degrees.

e) In the draw height=, enter 0.15.

This parameter sets the maximum height of the beads to be drawn.

f) Select buffer zone. This parameter establishes a buffer zone between elements in the design domain and elements outside the design domain. g) Toggle draw direction to normal to elements. This parameter defines the direction in which the shape variables are created. h) Set boundary skip to load and spc. This tells OptiStruct to leave nodes at which loads or constraints are applied out of the design space. i) Click update. A bead definition has been created for the design space tpg. Based on this information, OptiStruct will automatically generate bead variable definitions throughout the design variable domain. 5. Adding pattern grouping constraints. Use 1-plane symmetric beads, as it is the simplest and can be symmetric at the same time. a) Select the pattern grouping subpanel. b) Click desvar = and select tpg. c) Set the pattern type to 1-pln sym. d) Click anchor node, and enter 41 in the id= field.

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e) Click first node, and enter 53 in the id= field. f) Click update.

6. Update the bounds of the design variable. a) Select the bounds subpanel. b) Verify the desvar = field is set to tpg, which is the name of the design space. c) In the Upper Bound= field, enter 1.0.

Upper bound on variables controlling grid movement (Real > LB, default = 1.0). This sets the upper bound on grid movement equal to UB*HGT.

d) In the Lower Bound= field, enter 0.0. e) Click update.

The upper bound sets the upper bound on grid movement equal to UB*HGT and the lower bound sets the lower bound on grid movement equal to LB*HGT. 7. Click return to go to the Optimization panel.

Creating Optimization Responses Since this problem is a combined linear static and normal mode analysis, you are trying to minimize compliance and increase frequency for the two load cases, while constraining the seventh frequency. Therefore, two responses are defined: freq and comb. 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the frequency response. a) In the responses= field, enter freq.

b) Below response type, select frequency. c) For Mode Number, enter 7.0. d) Click create.

A response, freq, is defined for the frequency of the seventh mode extracted. 4. Create the compliance index response. a) In the response= field, enter comb.

b) Set the response type to compliance index. c) Using the loadsteps selector, select force. d) Toggle the option to define the normalizing factor to autonorm. e) In the Mode and Weight fields, enter the mode numbers and their corresponding weights. Mode

Weight

1

1.0

2

2.0

3

1.0

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Mode

Weight

4

1.0

5

1.0

6

1.0

f) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter frequency. 3. Click response = and select freq.

4. Check the box next to lower bound, then enter 12. 5. Using the loadsteps selector, select frequency. 6. Click create. 7. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select comb. 4. Click create. 5. Click return twice to exit the Optimization panel.

Defining Optimization Control Cards 1. From the Analysis page, click the Optimization panel. 2. Click the opti control panel. 3. Select MINDIM, and enter 0.25.

Minimum member size is generally recommended to avoid checkerboarding. It also ensures that the structure has the minimum dimension specified in this card.

4. Select MATINIT, and enter 1.0.

MATINIT declares the initial material fraction in a topology optimization. MATINIT has several defaults based upon the following conditions: If mass is the objective function, the MATINIT default is 0.9. With constrained mass, the default is reset to the constraint value. If mass is not the objective function and is not constrained, the default is 0.6.

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5. Click return twice to exit the panel.

Setting Mode Tracking During the optimization, the frequencies and their mode shape may change order due to the change in element densities and other design changes. To overcome this, define a parameter to track the frequencies so that only the intended frequencies are tracked during optimization runs. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click PARAM. 3. Select MODETRAK. 4. Set MODET_V1 to Yes. 5. Click return. The PARAM button is now green, indicating that it is active. 6. Click return to go back to the Analysis page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter comb_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file comb_complete.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results

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Post-Processing the Shape Results Change (Topography) 1. From the OptiStruct panel, click HyperView. HyperView is launched. 2.

On the Results toolbar, click

to open the Deformed panel.

3. Under Deformed shape, define deformed shape settings. a) Set the Result type to Shape Change(v). b) Set Scale to Scale factor. c) Set Type to Uniform. d) In the Value field, enter 1.0.

4. Under Undeformed shape, set Show to None. 5. Click Apply. The shape change due to the topography optimization displays. 6. In the Results Browser, set the Load Case and Simulation Selection to 25th iteration.

Figure 641: Topography Result Applied on Slider Suspension

Contouring the Optimum Material Distribution (Topologic) 1. On the Results toolbar, click

to open the Contour panel.

2. Set the Result Type to Element Densities (s) and Density. 3. Set the Averaging method to Simple. 4. Click Apply to display the density contour.

Adding Iso Surface of the Optimum Material Distribution (Topologic)

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OptiStruct Tutorials Combination Optimization 1. On the Results toolbar, click

p.699 to open the Iso Value panel.

2. Set the Result Type to Element Densities (s) and Density. 3. Set Show values to Above. 4. Click Apply to display the density iso-surface plot. 5. In the Current value field, enter 0.3. An iso-surface plot is displayed. Those parts of the model with a density greater than the value of 0.3 are shown in with density contour, the rest are removed from the display.

Figure 642:

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OS-T: 3200 Design of a Composite Aircraft Underbelly Fairing Composite materials have become popular in the application of aircraft structures. The need for innovative designs has posed a great challenge. In this tutorial you will perform an optimization-driven design approach of a composite aircraft underbelly fairing using OptiStruct. The design takes a three-phased approach: Phase 1: Reference Design Synthesis (Free-Size Optimization)

Concept design synthesis Free-size optimization identifies the optimal ply shapes and locations of patches per ply orientation.

Phase 2: Design Fine Tuning (Size Optimization)

Design fine tuning Size optimization identifies the optimal thicknesses of each ply bundle.

Phase 3: Ply Stacking Sequence Ply stacking sequence optimization Shuffling optimization obtains Optimization an optimal stacking sequence. The process expands upon three important and advanced optimization techniques; free-size optimization, size optimization and ply stacking sequence optimization. By stringing these three techniques together, OptiStruct offers a unique and comprehensive process for the design and optimization of composite laminates. The process is automated and integrated in HyperWorks by generating the input data for a subsequent phase automatically from the previous design phase.

Model Definition The finite element model of the underbelly fairing was generated in HyperMesh. Material properties for carbon-fiber were considered and represented using an orthotropic material (MAT8) for two dimensional elements. The fairing was modeled with four ply orientations (0°, 90°, 45° and -45°) of uniform thickness. The SMEAR option is applied in the PCOMP card to eliminate stack biasing. Two load cases were defined to represent the operating conditions - an internal uniform pressure loading of 0.02MPa and an external gravity loading of 6.75g. The fairing was considered to be riveted along its edges to the surrounding structure. Two equipment masses, weighing 2Kg and 3Kg each, were mounted to the fairing through RBE3 elements. The fairing has been designed considering two major performance criteria: the first natural frequency is at least 20Hz, and the maximum strain is less than 1000 micro-strain.

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Figure 643:

Phase 1: Reference Design Synthesis (Free-Size Optimization) In free-size optimization, the thickness of each designable element is defined as a design variable. Applying this concept to the design of composites implies that the design variables are the thickness of each Super-ply (total designable thickness of a ply orientation) per element. The following optimization setup is defined in the concept design phase to identify the stiffest design for the given fraction of the material. To obtain more meaningful results, manufacturing constraints are incorporated and carried through all design phases automatically. Objective

Minimize the weighted compliance of the two load cases.

Constraints

Volume fraction < 0.3

Design Variables

Element thicknesses of each ply orientation.

Manufacturing Constraints

Ply percentage for the 0s no more than 80% exist. The manufacturable ply thickness is 0.1. A balance constraint that ensures an equal thickness distribution for the +45s and -45s.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK.

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This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the fairing.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Creating Free-size Optimization Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the free size panel. 3. Create the design variable fairing. a) Select the create subpanel. b) In the desvar= field, enter fairing. c) Set type to PCOMP(G).

d) Using the props selector, select fairing_ply. e) Click create subpanel. The design variable fairing is created for the free-size optimization. 4. Define the manufacturing constraints on ply percentage and ply balance. a) Select the composites subpanel. b) Verify fairing is selected in the desvar= field. c) Click edit. d) In the DSIZE card image, select PLYPCT. e) Set Ply Percentage Options to BYANG. f) In the DSIZE_NUMBER_OF_PLYPCT = field, enter 1. A PLYPCT continuation line is added to the DSIZE data entry. g) Select PLYMAN. A PLYMAN continuation line is added to the DSIZE data entry.

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OptiStruct Tutorials Combination Optimization h) Select BALANCE. i) In the DSIZE_NUMBER_OF_BALANCE= field, 1. A BALANCE continuation line is added to the DSIZE data entry. j) Define the PLYPCT, BALANCE and PLYMAN constraints as shown in Figure 644.

Figure 644: DSIZE Data Entry Fields

k) Click return to go back to the composites panel. l) Click update. 5. Click return and go back to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the weighted component response. a) In the responses= field, enter wcomp.

b) Below response type, select weighted comp. c) Click loadsteps, then select all loadsteps. d) Change the weighting factors for gravity and pressure to 1.0. e) Click return. f) Click create. 5. Click return to go back to the Optimization panel.

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Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter con_vol. 3. Click response = and select volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select wcomp. 4. Click create. 5. Click return twice to exit the Optimization panel.

Defining the Output Request In this step you will define the output control on composite strain and stress results. OUTPUT,FSTOSZ (free size to size) is used to output a ply-based input deck for size optimization. 1. From the Analysis page, click the control cards panel. 2. Define the GLOBAL_OUTPUT_REQUEST card. a) In the Card Image dialog, click GLOBAL_OUTPUT_REQUEST. b) Select CSTRAIN and CSTRESS. c) Define the options shown in Figure 645 to output all composite strain and composite stress results for all elements to the H3D file. d) Click return.

Figure 645: Requesting CSTRAIN and CSTRESS results output to the .h3d file

3. Define the OUTPUT card.

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a) Click OUTPUT. b) In the number_of_outputs field, enter 1. c) Set KEYWORD to FSTOSZ. d) Set FREQ to YES. e) Click return. OptiStruct automatically generates a sizing model after free-size optimization.

Figure 646: Requesting the free-size to size (FSTOSZ) optimization output file for Phase 2

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter fairing_freesize for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file fairing_freesize.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include:

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fairing_freesize.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the fairing_freesize.fem file. fairing_freesize_des.h3d HyperView binary results file that contain optimization results. fairing_freesize_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. fairing_freesize_sizing.*.fem A ply-based sizing optimization input file generated during free-sizing phase. This resulting deck contains PCOMPP, STACK, PLY, and SET cards describing the ply-based composite model, as well as DCOMP, DESVAR, and DVPREL cards defining the optimization data. The * sign represents the final iteration number. fairing_freesize_sizing.*.inc An ASCII include file contains the same ply-based modeling and optimization data as in the input deck. The * sign represents the final iteration number.

Viewing the Results Viewing the Element Thickness Results 1. From the OptiStruct panel, click HyperView. HyperView launches and opens the fairing_freesize.mvw session file, which contains three pages with the results from three H3D files. Page 1

Optimization results in fairing_freesize_des.h3d.

Page 2

Analysis results of subcase 1 in fairing_freesize_s1.h3d.

Page 3

Analysis results of subcase 2 in fairing_freesize_s2.h3d.

2. Verify that you are on page 1. 3. On the Results toolbar, click

to open the Contour panel.

4. In the Results Browser, select the last iteration.

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Figure 647: Selecting the Final Iteration

5. Click Apply. 6. On the Standard Views toolbar, click

to view the results in the X-Y plane.

The element thickness results from the free-size optimization are shown in the following image. The regions indicated in red or in colors tending towards red (from the legend) can be interpreted as thicker regions, while those in blue or tending towards blue are thinner regions. The contour plot indicated above is the total thickness distribution that includes contributions from each ply orientation, i.e. a thickness contribution from the 0s, +/-45s and the 90s. It also indicates the shape and layout of plies per orientation as can be seen in the ply thickness plot.

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Figure 648: Element Thicknesses Contour Plot after Free-size Optimization

Viewing the Ply Thickness Results 1. From the Contour panel, set the Result type to Ply Thicknesses (s). 2. Select the other plot options as indicated in Figure 649.

Figure 649: Ply Thicknesses Contour Plot

3. In the Results Browser, select the last iteration. 4. Click Apply. The thickness distribution of 0 degree super ply is generated. It represents the ply shapes and patch locations of the 0 degree ply bundles.

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Figure 650: Ply Thickness Contour Plot of the 0 degree super-ply

5. Create the ply thickness contours for super-ply 2 (45°), 3 (-45°), and 4 (90°) by selecting Layers 2, 3 and 4, respectively in the Contour panel. Due to the balance constraint applied, the thickness distribution of the +45° and the -45° super ply are the same.

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Figure 651: Ply Thickness Contour Plot of the -45/+45 degree super-plies

Figure 652: Ply Thickness Contour Plot of the 90 degree super-ply

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Viewing the Ply Bundles through Element Sets The optimized 'Super-ply' thickness is subsequently represented as 'Ply Bundles'. Four ply bundles per fiber orientation (Super ply) are output by default, based on an intelligent algorithm in OptiStruct. These ply bundles represent the shape and location of the plies per fiber orientation through element sets. In this case, a total of 16 ply bundles are created after free size optimization converges: element sets 1 through 4 represent the ply bundles for 0 degree super-ply; element sets 5 through 8 represent ply bundles for +45° super-ply; element sets 9 through 12 represent ply bundle -45° super-ply; element sets 13 through 16 represent ply bundles for 90° super-ply. 1. Go back to the HyperMesh session. 2. Import the solver deck fairing_freesize_sizing.*.inc, located in the same directory where the file fairing_freesize.fem, into the current session.

3. In the Model Browser, right-click on the Load Collectors folder and select Hide from the context menu. The display of all load collectors is turned off. 4. From the Analysis page, click the entity sets panel. 5. Click review and select set 5. set 5 represents the ply bundle 1 of the +45° orientation super-ply. Tip: You can review ply bundles in the Model Browser, Plies folder. Click any ply to view it's corresponding card data in the Entity Editor.

Figure 653: Element set 5 representing ply bundle 1 of the +45 degree super ply

6. Review the element sets 6 though 8.

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Figure 654: Element set 6 representing ply bundle 2 of the +45 degree super ply

Figure 655: Element set 7 representing ply bundle 3 of the +45 degree super ply

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Figure 656: Element set 8 representing ply bundle 4 of the +45 degree super ply

The shapes of the plies as indicated through the element set can be used as-is in design Phase 2: Design Fine Tuning (Size Optimization), or modified easily by updating the element sets in HyperMesh to improve the manufacturability. In this case, the element sets are used as-is.

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Phase 2: Design Fine Tuning (Size Optimization) In the second design phase, a size optimization is performed to fine tune the thicknesses of the optimized ply bundles from Phase 1: Reference Design Synthesis (Free-Size Optimization). To ensure that the optimization design meets the design requirements, additional performance criteria on natural frequencies and composite strains are incorporated into the problem formulation. A normal modes analysis load case is added to calculate the natural frequencies of the fairing under assembled conditions. The optimization setup is also modified to factor in these additional performance targets, among others. The following is the modified optimization setup: Design Variables

Ply thicknesses, which have been defined in the size input deck from Phase 1: Reference Design Synthesis (Free-Size Optimization).

Objective

Minimize the total designable volume.

Constraints

Natural frequencies (1st ~ 5th) > 0.02 KHz Composite strains in the fairing < 1000 micro-strain

Manufacturing constraints are preserved and transferred to the DCOMP card. A minimum manufacturable ply thickness of 0.1, defined in Phase 1: Reference Design Synthesis (Free-Size Optimization), is transferred to the PLY card. It allows for the optimal ply bundle thicknesses to be a multiple of the minimum ply thickness value, and helps in calculating the total number of plies required per fiber orientation.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the fairing_freesize.*.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Reviewing Size Optimization Design Variables Size design variables were generated automatically at the free-size stage.

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1. From the Analysis page, click the optimization panel. 2. Click the size panel. 3. Review the size design variables.

Figure 657:

4. Click return to exit the size panel.

Reviewing the Manufacturing Constraints The manufacturing constraints were carried over to the size optimization phase automatically. They can be reviewed in the composite size panel in HyperMesh. 1. From the Optimization panel, click the composite size panel. 2. Select the parameters subpanel. 3. Click dcomp= and select DCOMP9. 4. Click edit. 5. Review the DCOMP card image.

PLYPCT and BALANCE constraints (from DSIZE) are transferred to the DCOMP card. The manufacturable ply thickness constraint 0.1 in the PLYMAN continuation line (from DSIZE) is transferred to the PLY card.

Figure 658: DCOMP Entry

6. Select the parameters subpanel. 7. Click update. 8. Click return twice to go back to the main menu.

Deleting Responses in the Free-size Optimization The optimization will be re-formulated to satisfy the main design requirements. The responses of weighted compliance and volume fraction used in the free-size phase will be removed.

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OptiStruct Tutorials Combination Optimization 1. On the Collectors toolbar, click

p.716 to open the Delete panel.

2. Set the entity selector to optiresponses. 3. Click optiresponses and select wcomp and volfrac. 4. Click select. 5. Click delete entity. 6. Click return. The responses defined in free-sizing phase are deleted. The constraint and objective function defined based on them are automatically removed.

Creating Normal Modes Analysis Add a normal modes analysis to calculate the natural frequencies. 1. Create the load collector, eigrl.

a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) In the Name field, enter eigrl.

c) Click Color and select a color from the color palette. d) Set Card Image to EIGRL. e) For ND, enter 8.

This request the first 8 modes.

2. Create the load step, norm_modes. a) In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. b) In the Name field, enter norm_modes.

c) Click Color and select a color from the color palette. d) Set the Analysis type to normal modes. e) For SPC, click Unspecified > Loadcol. In the Select Loadcol dialog, select spc and click OK. f) For METHOD(STRUCT), click Unspecified > Loadcol. In the Select Loadcol dialog, select eigrl and click OK.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter volume. b) Below response type, select volume.

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c) Set regional selection to total and no regionid. d) Click create. 4. Create the frequency response. a) In the responses= field, enter freq1.

b) Below response type, select frequency. c) For Mode Number, enter 1.0. d) Click create.

A response, freq1, is defined for the frequency of the first mode extracted. 5. Create frequency responses for mode 2, 3, 4, and 5. 6. Create a composite strain response. a) In the response= field, enter cstrain.

b) Set the response type to composite strain. c) Set the entity selector to plies, then use the plies selector to select all plies. d) Set the strain type to maj. Principle. e) Click create. 7. Click return to go back to the Optimization panel.

Creating Constraints The responses of frequency and composite strain are defined as the optimization constraints. 1. From the Optimization panel, click the dconstraint panel. 2. Create the constraint, freq1.

a) In the constraint= field, enter freq1. b) Click response= and select freq1.

c) Check the box next to lower bound, then enter 0.02. d) Using the loadsteps select, select norm_modes. e) Click create. 3. Repeat step 2 to create the constraints freq2, freq3, freq4, and freq5 respectively with the same lower bound of 0.02. 4. Create the constraint, cstrain.

a) In the constraint= field, enter cstrain. b) Click response= and select cstrain.

c) Check the box next to upper bound, then enter 0.001.

d) Using the loadsteps select, select gravity and pressure. e) Click create. 5. Click return to go back to the Optimization panel.

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Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

Defining the Output Request for Shuffling Deck The output control on composite strain and stress results defined in the previous phase are carried over automatically. OUTPUT,SZTOSH (sizing to shuffling) writes a ply stacking optimization input deck. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click OUTPUT. 3. Set KEYWORD to SZTOSH. 4. Set FREQ to YES. 5. In the number_of_outputs field, enter 1.

Figure 659:

6. Click return twice to go back to the Analysis page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter fairing_size for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization.

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7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file fairing_size.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: fairing_size.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the fairing_size.fem file. fairing_size_des.h3d HyperView binary results file that contain optimization results. fairing_size_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. fairing_size_shuffling.*.fem A ply stacking optimization input deck. The DESVAR and DVPREL cards from the previous stage are removed, and a bare DSHUFFLE card is introduced. The * sign represents the final iteration number. fairing_size_shuffling.*.inc An ASCII include file containing ply stacking optimization data.

Viewing the Results 1. From the OptiStruct panel, click HyperView. 2. On the Results toolbar, click

to open the Contour panel.

3. In the Results Browser, select the last iteration. 4. Click Apply. The element thickness contour plot (final iteration) after phase-2 size optimization displays.

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Figure 660:

5. In the Contour panel, set the Result type to Orientation Thicknesses (s). The thickness contour for each ply orientation displays. 6. Set the Result type to Ply Thicknesses (s). The thickness contour for each ply bundle displays. After the free-size and size optimizations, a weight reduction of ~65% of the original design was achieved without violating any of the prescribed design constraints. The optimum ply shape and patch locations in Phase 1: Reference Design Synthesis (Free-Size Optimization), and subsequently optimized ply bundle thicknesses in Phase 2: Design Fine Tuning (Size Optimization), have been established, and allow us to determine the required number of plies. In the third and final phase of the design process you will try to identify a proposal for the optimal stacking sequence of the plies.

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Phase 3: Ply Stacking Sequence Optimization This algorithm is aimed at providing a global view of what the optimal stacking sequence could be. An input deck for the ply stacking sequence optimization, fairing_size_shuffling.*.fem, was generated from a previous design stage. Each ply bundle is divided into multiple PLYs whose thickness is equal to the manufacturable thickness (0.1 in this case), and the STACK card is updated accordingly. In this design phase, composite plies are shuffled to determine the optimal stacking sequence. It is important that design performances are preserved. Hence, the optimization problem is retained as previously formulated in the size optimization phase. Two manufacturing constraints are applied: • The maximum successive number of plies of a particular orientation does not exceed 4 plies. • The + 45s and - 45s are reversed paired.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the fairing_size_shuffling.*.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Updating the Composite Strain Response Since the ply bundles were divided into multiple plies in the shuffling model, the ply information in CSTRAIN response needs to be updated, as well. 1. From the Analysis page, click the optimization panel. 2. Click the responses panel. 3. Click response= and select cstrain. 4. Using the plies selector, select all of the plies. 5. Click update. 6. Click return.

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Creating the Manufacturing Constraints for Shuffling A DSHUFFLE card was created automatically during the sizing phase. Two manufacturing constraints will be added for the shuffling optimization. 1. From the Optimization panel, click the composite shuffle panel. 2. Select the create subpanel. 3. Click dshuffle= and select DSHUFFLE1. Review the type and stack ID. 4. Select the parameters subpanel. 5. Click dshuffle = and select DSHUFFLE1. 6. Select pairing constraint. 7. Set the pair type to reverse. 8. In the ply angles1 field, enter 45.0.

9. In the ply angles2 field, enter -45.0. 10. Click update. 11. Click edit. 12. Define the MAXSUCC constraint, as shown in Figure 661.

Figure 661:

13. Click return. 14. Click update. 15. Click return twice to go back to the Analysis page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter fairing_shuffling for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save.

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The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file fairing_shuffling.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Open the fairing_shuffling.shuf.html file in your Internet browser. The history of the shuffling optimization displays. The columns represent the global trend of the ply stacking sequence at a particular iteration, with the last column being the final solution. The plies are color coded based on their fiber orientations. The weight of the fairing has not been changed during the shuffling design phase.

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Figure 662: Shuffling Optimization History

Reviewing the results from this process: • Lowest natural frequency = 0.02 KHz (>0.02 KHz)

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OptiStruct Tutorials Combination Optimization • Maximum strain = 9.947e-4 ( Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the controlarm.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Adding LATTICE Continuation Card to the DTPL Card 1. Close HyperMesh Desktop. 2. In a text editor, open controlarm.fem.

3. Locate the optimization data in the deck. The DTPL card contains the data on the design space.

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Figure 666:

4. Below the DTPL line, enter + LATTICE 1 0.1 0.7 200.

Each field begins with the field's data and is padded with spaces to a total of 8 characters long.

Figure 667:

Field Descriptions +

A continuation of the preceding line/card, DTPL

LATTICE

This optimization should use lattice (porous) topology parameters.

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Field Descriptions 1

Sets the lattice type (LT) according to the solid element type that it is replacing. 1 is the default or enter 2 as an option. Element Types CHEXA

By default, this generates pyramidal lattices with quadrilateral bases and triangular internal adjoining faces. For option 2, it creates a tetrahedral matrix to replace the CHEXA element.

CPENTA

This creates a pair of lattices, one pyramidal, one tetrahedral regardless of setting (1 or 2).

CPYRA

This creates a pyramidal lattice regardless of setting (1 or 2).

CTETRA

This creates a tetrahedral lattice regardless of setting (1 or 2).

0.1

The lower bound (LB) for lattice structure. Any elements with a topology density below this value is considered void (empty) at the end of Phase I.

0.7

The upper bound (UB) for lattice structure. Anything above this element density in the optimization is considered fully solid. Elements where element density is between the lower and upper bound are considered porous and is replaced by lattice elements at the end of Phase I.

200.

Sets a stress constraint target for optimization for the second phase of lattice optimization (LATSTR). That means for Phase II, OptiStruct will automatically create a stress constraint (refer to Lattice Structure Optimization in the User Guide). The stress target for Phase I (via the STRESS continuation card which was already present in this deck and set to 200), is not automatically "copied" to Phase II.

5. Save controlarm.fem.

Adding DOPTPRM Optimization Parameters 1. Below the final stress continuation card for the DTPL entry, add: DOPTPRM,POROSITY,MED DOPTPRM,LATLB,CHECK

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DOPTPRM indicates that optimization parameters to control the optimization are being added. DOPTPRM, POROSITY determines the penalty factor applied to all designable elements throughout the optimization. In regular topology optimization, a penalty is applied to avoid medium dense elements by significantly reducing their stiffness. In Lattice optimization, medium dense elements can be accepted as they can be manufactured as a lattice structure. You can apply a smaller penalty or nothing, which controls the number of medium dense elements and consequently lattice type elements. This parameter has three options: LOW: Sets the penalty factor to 1.8. This setting accurately represents the structural relationship between intermediate dense solid elements and lattice type elements, which result in a model that has few lattice elements, as medium dense elements are widely removed, due to the penalty. MED: Sets the penalty factor to 1.25. This penalizes intermediate dense elements to some extent and results in a moderate presence of lattice zones. HIGH: Sets the penalty factor to 1, negating any penalty to the Young's Modulus and density relationship. This usually leads to a high number of lattice elements, but also produces a mathematical over-estimation of stiffness for structures known to be porous, which leads to a larger discrepancy between the structural performance of Phases I and II. In some cases a certain value for LB can lead to important parts of the structure being interpreted as void. For instance, for a high number, such as 0.5 or where important parts of the structure have low densities. In those cases, the removal of the void elements can lead to a non-functioning structure. DOPTPRM, LATLB aims at preventing such scenarios. It will force OptiStruct to check the structure for large differences in compliance between the final iteration of Phase I and the one where the elements with density below LB are removed. If the structure is found to be too 'soft', the lower bound for lattice zones can be adjusted downward during the optimization to create a more continuous or stiff structure that more closely represents the original mesh. This parameter has the following options: CHECK: Requests that OptiStruct check the lattice optimized representation of the model for differences in compliance. AUTO: Allows OptiStruct to automatically adjust the lower bound of the lattice-optimized model downward to increase the model continuity. NONE: No check for performance loss is made.

Figure 668:

2. Save controlarm.fem.

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Running the Optimization 1. Open the HyperWorks Solver Run Manager. 2. Open the controlarm.fem file.

3. Click Run to run the optimization.

Figure 669:

4. When the optimization has completed, open the controlarm.fem file in a text editor.

5. Check how the optimization progressed. Make sure that the optimization is fully converged and that the constraint is satisfied. OptiStruct provides a summary of the lattice optimization and its effects on the model, at the end of the output file.

Figure 670:

Since DOPTPRM, LATLB, CHECK was applied, OptiStruct checked the drop-in compliance, due to the removal of elements with density below LB. The drop is relatively small and this LB can be considered a good choice.

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Phase 2: Design Fine Tuning Opening and Reviewing the Model At the end of Phase I, OptiStruct automatically created a new file, controlarm_lattice.fem, from your original optimization model. In this model, the original designable elements with a density below LB have been removed, those above UP remain unchanged and those in-between are replaced by bars (CBAR) representing the lattice structure. The second phase of this optimization will optimize the radius of each joint in the lattice structure to determine where there is a need for material. The necessary design variables (DESVAR) and design variable property relationships (DVPREL1), along with the stress constraints are automatically created. In many cases, the model can be run as is, but it is advised to always review the optimization setup. 1. In a text editor, open controlarm_lattice.fem. 2. Review the model.

a) The beginning of the deck shows that the new file has retained your original objective, but added a new optimization parameter indicating that this size optimization is Phase II of a lattice structure optimization.

Figure 671:

b) OptiStruct has inserted the CBAR elements, which represent the new lattice material, below the GRID cards, which provides details about the model nodes.

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Figure 672:

c) Each CBAR element has its own PBAR property definition, listed later in the deck, which indicates each element can be individually optimized.

Figure 673:

d) Each joint between multiple CBAR elements has a design variable created for it.

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Figure 674:

e) At the end of the file are the design variable property relationships (DVPREL1), which relate properties to their associated design variable for the size optimization in the second phase. These are followed by the responses, the constraints, and the objective. Note: The volume fraction response in the original model has been replaced by total volume in the size optimization phase, which will now be minimized and a new response has been added to constrain the von Mises stress in the lattice region to 200. This was created from the value in the last field of the LATTICE continuation card in the first phase.

Figure 675:

3. Close the controlarm_lattice.fem file in the text editor.

Running the Optimization 1. Open the HyperWorks Solver Run Manager.

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2. Open the controlarm_lattice.fem file. 3. Click Run to run the optimization.

Figure 676:

4. When the optimization has completed, open the controlarm_lattice.fem file in a text editor to review critical information about the optimization run. 5. Verify that the optimization is fully converged and that the constraint is satisfied.

Figure 677:

The difference in lattice penalty (lower than 1.8, set by the optimization parameters) causes the compliance of the final Phase I model to differ from the initial Phase II model. This compliance difference is also affected by solid elements retained in the Phase II model, which recover their full density/stiffness. For this reason, post-processing a lattice optimization requires that you analyze changes to the model compliance between the Phase I final optimization compliance and the Phase II initial compliance calculation and again at the end of Phase II. 6. Open the HyperWorks Solver Run Manager. 7. Open the controlarm_lattice_optimized.fem file. 8. Click Run for verification purposes.

Since the optimization removes CBAR elements of small radius after the last optimization, the compliance for the last optimized run should be confirmed against the controlarm_lattice_optimized.fem file, an analysis of the optimized structure provided by OptiStruct.

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Figure 678:

9. Compare the final compliance between the controlarm_lattice.out and controlarm_lattice_optimized.out files.

Figure 679: Final Compliance from the Optimization Run

Figure 680: Final Compliance from the Analysis Model

Post-processing the Results 1. Open HyperMesh Desktop. 2. Import the file controlarm_lattice_optimized.fem into a new session.

3. On the Visualization toolbar, from the 1D Element Representation menu, select 1D Detailed Element Representation. The CBAR elements in the model with their radii applied display.

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Figure 681: View of the Optimized Solid/Lattice Model

Figure 682: Front View of the Optimized Lattice/Solid Model Showing the Variation in CBAR Radius

4. In a new HyperView session, load the file controlarm_lattice_s1.h3d.

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5. Edit visualization options. a) From the menu bar, click Preferences > Options. b) In the Options dialog, select the Visualization section. c) Select Enable element marks. d) Set the BAR representation to Cylinder. e) In the Size of mark (model %), enter 0.125. f) Click Apply. g) Click OK.

Figure 683:

6. On the Results toolbar, click

to open the Contour panel.

7. Set the type to CBAR/CBEAM Stresses (ROD). 8. Set the Subtype to NORMAL S1N(A). 9. Click Apply. The beam element visualization is contoured.

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Figure 684: Iteration 0 (Initial Sizing Design)

Figure 685: Last Iteration (Final Design)

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OS-T: 3400 Design an Open Hole Tension (OHT) Composite materials have become popular in the application of a variety of structures. The need for innovative designs has posed a great challenge. In this tutorial you will perform an optimization-driven design approach of an open-hole tension specimen using OptiStruct. The design takes a three-phased approach: Phase 1: Reference Design Synthesis (Free-size Optimization)

Concept design synthesis Free-size optimization identifies the optimal ply shapes and locations of patches per ply orientation.

Phase 2: Design Fine Tuning (Size Optimization)

Design fine tuning Size optimization identifies the optimal thicknesses of each ply bundle.

Phase 3: Ply Stacking Sequence Ply stacking sequence optimization Shuffling optimization obtains Optimization an optimal stacking sequence. The process expands upon three important and advanced optimization techniques; free-size optimization, size optimization and ply stacking sequence optimization. By stringing these three techniques together, OptiStruct offers a unique and comprehensive process for the design and optimization of composite laminates. The process is automated and integrated in HyperWorks by generating the input data for a subsequent phase automatically from the previous design phase. Together with these steps, an initial and final analysis will be utilized to determine the baseline and final characteristics of the designed part.

Model Definition The composite design optimization methodology presented within this tutorial was developed to solve very complex composite design optimization problems. The methodology breaks down the complex composite design optimization problem, which is not solvable by itself, into several simpler composite design optimization problems, which are solvable by themselves. The cumulative solution to each of the simpler composite design optimization problems provides a solution to the complex design optimization problem. This process of breaking down complex problems into several simpler problems is consistent with the engineering method.

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Figure 686: Model Overview

Model Setup and Baseline Analysis The following set of steps completes the analysis setup of the initial model and provides a baseline analysis for comparison with the final optimized structure.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the oht_analysis.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The oht_analysis.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Setting Up the Model Creating Carbon Epoxy Material 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter carbonepxy.

3. Set the Card Image to MAT8. 4. Enter the values shown in Figure 687.

Figure 687:

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Creating Element Set 1. In the Model Browser, right-click and select Create > Set from the context menu. A default set displays in the Entity Editor. 2. For Name, enter ply_shape.

3. Set the Card Image to SET_ELEM. 4. For Entity IDs, click 0 Elements > Elements. 5. Using the elems selector, select all of the elements in the model. 6. Click proceed to continue.

Creating Basic Plies 1. In the Model Browser, right-click and select Create > Ply from the context menu. The Create Ply dialog opens. 2. Create a ply named ply1. a) For Name, enter ply1.

b) Set the Material type to ORTHOTROPIC. c) Set Material to carbonepxy. d) For Thickness, enter 0.1.

e) For Orientation, enter 0.0.

f) Set the Shape selector to Set, then use the Sets selector to select the ply_shape set. g) Select Output results. h) Click Create.

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Figure 688:

3. Create a ply named ply2 with an orientation of 90. 4. Create a ply named ply3 with an orientation of 45. 5. Create a ply named ply4 with an orientation of -45. 6. Click Close to exit the dialog.

Creating Laminate 1. In the Model Browser, right-click and select Create > Laminate from the context menu. The Create Laminate dialog opens.

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2. For Name, enter laminate. 3. Set Card image to STACK.

4. Set Laminate option to Smear. 5. In the Define laminate section, select ply1 for the first row, with each successive ply on a consecutive row. Leave all other parameters set as default. 6. Click Create to create the laminate. 7. Click Close to exit the dialog.

Figure 689:

Creating and Assigning a Property 1. Create the property, laminate_property. a) In the Model Browser, right-click and select Create > Property from the context menu. A default property displays in the Entity Editor. b) For Name, enter laminate_property.

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c) Set Card Image to PCOMPP. 2. Assign elements to the property, laminate_property. a) In the Model Browser, Properties folder, right-click on laminate_property and select Assign from the context menu. b) In the panel area, use the elems selector to select all elements in the model. c) Click proceed.

Reviewing the Model 1. On the Visualization toolbar, click

to set the element visualization mode to 2D Detailed

Element Representation. This will thicken all shells in the model to their total thickness, displaying them as 3-dimensional representations of their thicknesses. 2. Click

to set the layers mode to Composite Layers.

This separates the view into individual plies. 3. Set the element color mode to By Prop. This will assist you in determining which plies are which in the layup. Each of the plies in the model are color coded according to the color of its ply as shown in the Model Browser. If all of the plies in the model are the same color, change the ply colors in the Model Browser so that each is different to help differentiate the plies in the modeling window.

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Figure 690:

Creating Output Requests 1. From the Analysis page, click the control cards panel. The Card Image dialog opens. 2. Edit the GLOBAL_OUTPUT_REQUEST card. a) Click GLOBAL_OUTPUT_REQUEST. b) Select CSTRAIN. c) Set EXTRA(1) to MECH. d) Set OPTION(1) to ALL. e) Select DISPLACEMENT. f) Set OPTION(1) to ALL. g) Select STRESS. h) Set OPTION(1) to NO. i) Click return. This requests that NO homogeneous stress be output. This control card output must be explicitly added as a request since homogeneous stress is output by default. In turning it off, the values will not be calculated by the solver for output. 3. Edit the OUTPUT card. a) Click OUTPUT.

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b) In the number_of_outputs= field, enter 2.

c) For the first OUTPUT, set KEYWORD to HTML and set OPTION to NO. This turns off HTML output for all analyses and optimizations which have this keyword combination. d) For the second OUTPUT, set KEYWORD to H3D and set FREQ to FL. This request that OptiStruct's .h3d output file be output at the first (F) and last (L) iteration. For analysis, this does not matter, but for optimization it applies when you get to the optimization runs. 4. Click return twice to return to the Analysis page.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 691: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter oht_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the oht_analysis.fem was written. The oht_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results

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1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. On the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Composites Strains(Mech) (s). 4. Set the subtype to Normal X Strain. 5. To view the individual strain contributions from any one ply, select the appropriate ply name in the Layers drop-down. 6. Click Apply.

Figure 692:

Deactivating the Composite Visualization Enhancements 1. On the Page Controls toolbar, click

to close the HyperView session and return to the

HyperMesh client. 2. On the Visualization toolbar, change the visualization settings. a) Set the element visualization mode to 2D Traditional Element Representation. b) Set the layers mode to Layers Off. c) Set the element color mode to By Comp.

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Phase 1: Reference Design Synthesis (Free-size Optimization) In this phase the optimization setup is defined in the concept design phase to identify the stiffest design for the given fraction of the material. In free-size optimization, the thickness of each designable element is defined as a design variable. Applying this concept to the design of composites implies that the design variables are the thickness of each 'Super-ply' (total designable thickness of a ply orientation) per element. To obtain more meaningful results, manufacturing constraints are incorporated and carried through all design phases automatically. Objective

Minimize the compliance of the load case.

Constraints

Volume fraction < 0.3

Design Variables

Element thicknesses of each ply orientation.

Manufacturing Constraints

Ply percentage for the 0s no more than 80% exist. The manufacturable ply thickness is 0.1. A balance constraint that ensures an equal thickness distribution for the +45s and -45s.

Setting Up the Optimization Creating Free-size Optimization Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the free size panel. 3. Create the design variable for the free-size optimization. a) Select the create subpanel. b) In the desvar= field, enter free-size. c) Set type to STACK.

d) Using the laminates selector, select laminate. e) Click create.

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Figure 693: Field Entries for the free-size Panel

4. Select the composites subpanel. 5. Click the desvar= field and select free-size. 6. Click edit. The DSIZE panel opens. In this panel you will define the manufacturing constraints on ply percentage, ply balance, and ply drop-off. 7. Define PLYPCT. a) Select PLYPCT. b) Set Ply Percentage Options to BYANG. c) In the DSIZE_NUMBER_OF_PLYPCT= field, enter 2.

Two PLYPCT continuation lines are added to the DSIZE Data Entry.

d) In the first PLYPCT row, enter 0 for PANGLE(1), 0.2 for PPMIN(1), and 0.7 for PPMAX(1).

e) In the next PLYPCT row, enter 90 for PANGLE(2), 0.2 for PPMIN(2), and 0.7 for PPMAX(2).

These values constrain the zero- and ninety-degree plies to between twenty and seventy percent of the total thickness of the laminate for any element in the design space.

Figure 694: DSIZE Data Entry Fields for the PLYPCT Cards

8. Define BALANCE. a) Select BALANCE. b) Set Balance Constraints Options to BYANG. c) In the DSIZE_NUMBER_OF_BALANCE= field, enter 1. A BALANCE continuation line is added to the DSIZE Data Entry.

d) In the BALANCE row, enter 45 for BANGLE1 and -45 for BANGLE2.

Figure 695: DSIZE Data Entry Fields for the BALANCE Card

9. Define PLYDRP. a) Select PLYDRP.

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OptiStruct Tutorials Combination Optimization A PLYDRP continuation line is added to the DSIZE Data Entry.

b) Set Ply Drop-off Options to All.

c) In the DSIZE_NUMBER_OF_PLYDRP= field, enter 1.

d) In the PLYDRP row, set PDTYP(1) to PLYSLP and for PDMAX(1) enter 0.33.

Figure 696: DSIZE Data Entry Fields for the PLYDRP Card Using the PLYSLP Method

10. Click return to go back to the composites subpanel. 11. Click update. 12. Click return and go back to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the compliance response. a) In the response= field, enter compliance. b) Below response type, select compliance.

c) Set regional selection to total and no regionid. d) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter volfrac. 3. Click response = and select volfrac.

4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

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Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select compliance. 4. Using the loadsteps selector, select nx_step. 5. Click create. 6. Click return twice to exit the Optimization panel.

Creating Output Requests The output control on composite strain and stress results are defined here. OUTPUT,FSTOSZ (free size to size) is used to output a ply-based input deck for size optimization. 1. From the Analysis page, select the control cards panel. 2. In the Card Image dialog, click OUTPUT. 3. In the number_of_outputs, enter 3.

4. On the third line, set KEYWORD to FSTOSZ and set FREQ to YES. With this keyword, OptiStruct automatically generates a sizing model after free-size optimization.

Figure 697: Requesting the free-size to size (FSTOSZ) optimization output file for Phase 2

5. Click return twice to go back to the Analysis page.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter oht_opti_ph1.hm for the file name and save it to your working directory.

Running the Optimization

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1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter oht_opti_ph1 for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file oht_opti_ph1.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: oht_opti_ph1.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the oht_opti_ph1.fem file. oht_opti_ph1_des.h3d HyperView binary results file that contain optimization results. oht_opti_ph1_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. oht_opti_ph1_sizing.*.fem A ply-based sizing optimization input file generated during free-sizing phase. This resulting deck contains PCOMPP, STACK, PLY, and SET cards describing the ply-based composite model, as well as DCOMP, DESVAR, and DVPREL cards defining the optimization data. The * sign represents the final iteration number. oht_opti_ph1_sizing.*.inc An ASCII include file contains the same ply-based modeling and optimization data as in the input deck. The * sign represents the final iteration number.

Viewing the Results

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Viewing the Element Thickness Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the session file oht_opti_ph1.mvw is opened, which contains three pages with the results from two H3D files. Page 2

Optimization results in oht_opti_ph1_des.h3d.

Page 3

Analysis results of subcase 1 in oht_opti_ph1_s1.h3d. Note: If opening these files from standalone HyperMesh, the page numbers will be decremented.

2. Navigate to the page with the results for oht_opti_ph1_des.h3d. 3. On the Results toolbar, click

to open the Contour panel.

4. Select the plot options.

Figure 698: Contour panel Plot Options (Free-Size Optimization Results)

5. In the Results Browser, select the last iteration.

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Figure 699: Selecting the Final Iteration

6. Click Apply. 7. On the Standard Views toolbar, click

to view the results in the X-Y plane.

The element thickness results from the free-size optimization are shown in the image below. The regions indicated in red or in colors tending towards red (from the legend) can be interpreted as thicker regions, while those in blue or tending towards blue are thinner regions. The contour plot indicated above is the total thickness distribution that includes contributions from each ply orientation, i.e. a thickness contribution from the 0s, +/-45s and the 90s. It also indicates the shape and layout of plies per orientation as can be seen in the ply thickness plot.

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Figure 700: Element Thicknesses Contour Plot After Free-size Optimization

Viewing the Ply Thickness Results 1. From the Contour panel, set the Result type to Ply Thicknesses (s). 2. Select the plot options.

Figure 701: Ply Thicknesses Contour Plot

3. In the Results Browser, select the last iteration. 4. Click Apply. The thickness distribution of 0 degree super ply is generated. It represents the ply shapes and patch locations of the 0 degree ply bundles.

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Figure 702: Ply Thickness Contour Plot of the 0 Degree Super-Ply

5. Create the ply thickness contours for super-ply 2 (45°), ply 3 (-45°), and ply 4 (90°) by selecting Layers 2, 3 and 4, respectively in the Contour panel. Due to the balance constraint applied, the thickness distribution of the +45° and the -45° super ply are the same.

Figure 703: Ply Thickness Contour Plot of the -45/+45 Degree Super-ply

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Figure 704: Ply Thickness Contour Plot of the 90 Degree Super-ply

Viewing the Ply Bundles The optimized 'Super-ply' thickness is subsequently represented as 'Ply Bundles'. Four ply bundles per fiber orientation (Super ply) are output by default, based on an intelligent algorithm in OptiStruct. These ply bundles represent the shape and location of the plies per fiber orientation through element sets. In this case, a total of 16 ply bundles are created after free size optimization converges: plies 1 through 4 represent the ply bundles for 0 degree super-ply; plies 5 through 8 represent ply bundles for 90 degree super-ply; plies 9 through 12 represent ply bundle +45 degree super-ply; and applies 13 through 16 represent ply bundles for -45 degree super-ply. 1. Go back to the HyperMesh and start a new model. 2. Import the solver deck oht_opti_ph1_sizing.*.inc, located in the same directory where the file oht_opti_ph1.fem, into the current session. 3. In the Model Browser, right-click on the Load Collectors folder and select Hide from the context menu. The display of all load collectors is turned off. 4. In the Model Browser, right-click on the Plies folder and select Hide from the context menu. The display of all plies is turned off. 5. In the Model Browser, Plies folder, activate the mesh view icon for each ply individually to review the plies.

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Figure 705: Model Browser View Showing Ply 11300 Selected (Laminate 1, Ply 1, Shape 3)

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Figure 706: Graphics Area View of Ply 11300 (Laminate 1, Ply 1, Shape 3)

The shapes of the plies as indicated through the element set can be used as-is in design Phase 2, or modified easily by updating the element sets in HyperMesh or using ply smoothing to improve the manufacturability. Ply smoothing operations are shown in the next section.

Applying Ply Smoothing using OSSmooth Ply smoothing is an automated method to further reduce the ply shapes into more manufactural ply shapes. Although ply smoothing significantly improves the ply shapes for manufacturability, often it is still necessary to manually edit the ply shapes after this step. 1. From the Post page, click the OSSmooth panel. 2. In the Select model field, select oht_opti_ph1_sizing.35.fem. 3. Change the mode from Geometry to PLY Shape.

4. In the output file field, select the original location with the name of oht_opti_ph1_sizing.35.smoothed.fem. 5. In the smooth iterations field, enter 20.

6. Under small region, clear the split disconnected and create geometry checkboxes. 7. In the area ratio field, enter 0.010.

8. Click OSSmooth to run the analysis to smooth the model.

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Figure 707: View of Ply 11300 after Smoothing Operations (Laminate 1, Ply 1, Shape 3)

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Phase 2: Design Fine Tuning (Size Optimization) In the second design phase, a size optimization is performed to fine tune the thicknesses of the optimized ply bundles from Phase 1. To ensure that the optimization design meets the design requirements, additional performance criteria on may be incorporated into the problem formulation. These new criteria will be fiber strain, matrix strain, and mass. The following is the modified optimization setup: Design Variables

Ply thicknesses, which have been defined in the size input deck from Phase 1.

Objective

Minimize the total mass.

Constraints

Fiber Strain < 9000 με (microstrain) Matrix Strain < 7000 με (microstrain)

Manufacturing constraints previously applied are preserved and transferred to the DCOMP card.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter oht_opti_ph2.hm for the file name and save it to your working directory.

Setting Up the Optimization Editing the Size Design Variables 1. From the Optimization panel, click the size panel. 2. Click review. 3. Select autoply. 4. In the initial value= field, enter 0.04. This is the thickness of four plies.

5. In the upper bound field=, enter 0.2. 6. In the lower bound field=, enter 0.0.

7. Click update to update the design variable. 8. Repeat the above steps to update the bounds and starting value for each size design variable.

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Note: The DESVARs have the same ID numbers as the design variable property relationship (DVPREL) that they relate to. These ID numbers also refer to the plies created in the previous optimization - in this way, they can easily be cross-referenced.

Editing the Manufacturable Thickness and Initial Value of Each Ply 1. In the Model Browser, Plies folder, select all plies.

Figure 708:

2. In the Entity Editor, edit the plies. a) For TMANUF, enter 0.01.

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b) For Thickness, enter 0.04.

This changes the values for all plies simultaneously.

Updating the Laminate Calculation Type 1. In the Model Browser, Laminates folder, right-click on laminate and select Edit from the context menu. 2. In the Laminate Edit dialog, set Laminate option to Symmetric smear. 3. Click Update to exit. The laminate option defines the laminate behavior. In this case SMEAR theory is used to define the laminate behavior; that is the A-matrix is calculated exactly since it is stacking sequence independent, the D-matrix is calculated as AT2/12, and finally the B-matrix is set to zero. Adding the Symmetric option to the SMEAR theory just assures a symmetric laminate will be output by adding/removing 2 plies at a time vs. 1 ply at a time.

Deleting the Existing Responses, Constraints and Objective 1. In the Model Browser, right-click and select Optimization > Response > Delete from the context menu. 2. HyperMesh asks you to confirm the delete. Click Yes to continue. When responses are deleted in HyperMesh, all constraints and objectives which depend on those responses are deleted.

Creating Size Optimization Responses The responses of volume, natural frequency, and composite strain are created for size optimization. 1. From the Analysis page, click the optimization panel. 2. Click the responses panel. 3. Create a fiber mechanical strain response. a) In the response= field, enter fiber_e.

b) Set response type to composite strain. c) Set component to mechanical. d) Set the entity selector to plies, then use the plies selector to select all plies in the mode. e) Set the response component to normal 1. f) Select all plies. g) Click create.

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Figure 709: Fiber Mechanical Strain Response

4. Create a matrix mechanical strain response. a) In the response= field, enter matrix_e.

b) Set response type to composite strain. c) Set component to mechanical. d) Set the entity selector to plies, then use the plies selector to select all plies in the mode. e) Set the response component to normal 2. f) Select all plies. g) Click create.

Figure 710: Matrix Mechanical Strain Response

5. Create the mass response. a) In the response= field, enter mass. b) Set response type to mass. c) Set type to total. d) Click create. 6. Click return to go back to Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter fiber_e. 3. Click response = and select fiber_e.

4. Check the box next to upper bound, then enter 0.009. 5. Using the loadsteps selector, select nx_step.

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6. Click create. 7. Create constraint matrix_e on response matrix_e for loadstep nx_step with an upper bound of 0.007. 8. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

Editing the Composite Size Design Variable 1. From the optimization panel, click the composite size panel. 2. Select the create subpanel. 3. Click review. 4. Select the free-size design variable. This DESVAR has been carried over from the previous optimization as a size optimization with manufacturing constraints preserved from the original optimization. 5. Select the parameters subpanel. 6. Under laminate thickness, toggle minimimum thickness off to minimum thickness, and enter 0.04. 7. Click edit.

8. Review the manufacturing constraints. a) Verify PLYPCT is set to restrict 0 and 90-degree plies to between 0.2 and 0.7. b) Verify BALANCE is set to 45 and -45 degree plies. c) Verify PLYDRP is still set to TOTAL with a PDMAX of 0.33. 9. Click return to keep these parameters. 10. Click update. 11. Click return twice to return to the Analysis page.

Defining the Output Request The output control on composite strain and stress results defined in the previous phase are carried over automatically. OUTPUT,SZTOSH (sizing to shuffling) writes a ply stacking optimization input deck. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click OUTPUT. 3. Set the final KEYWORD to SZTOSH.

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4. Set the FINAL FREQ to YES. 5. Click return.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter oht_opti_ph2 for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file oht_opti_ph2.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: oht_opti_ph2.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the oht_opti_ph2.fem file. oht_opti_ph2_des.h3d HyperView binary results file that contain optimization results. oht_opti_ph2_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. oht_opti_ph2_shuffling.*.fem A ply stacking optimization input deck. The DESVAR and DVPREL cards from the previous stage are removed, and a bare DSHUFFLE card is introduced. The * sign represents the final iteration number. oht_opti_ph2_shuffling.*.inc An ASCII include file containing ply stacking optimization data.

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Viewing the Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. Navigate to the page with the results for oht_opti_ph2_des.h3d. 3. On the Results toolbar, click

to open the Contour panel.

4. Set the Result type to Ply Thicknesses (s). 5. Select the plot options.

Figure 711: Ply Thicknesses Contour Plot

6. In the Results Browser, select the last iteration. 7. Click Apply. An element thickness contour plot (final iteration) after phase-2 size optimization displays.

Figure 712:

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Phase 3: Ply Stacking Sequence Optimization This algorithm is aimed at providing a global view of what the optimal stacking sequence could be. An input deck for the ply stacking sequence optimization, oht_opti_ph2_shuffling.*.fem, was generated from a previous design stage. Each ply bundle is divided into multiple PLYs whose thickness is equal to the manufacturable thickness (0.01 in this case), and the STACK card is updated accordingly. In this design phase, composite plies are shuffled to determine the optimal stacking sequence. It is important that design performances are preserved. Hence, the optimization problem is retained as previously formulated in the size optimization phase. Two manufacturing constraints are applied: • The maximum successive number of plies of a particular orientation does not exceed 4 plies. • The outermost four layers of the layup must be -45, 0, 45, 90.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the oht_opti_ph2_shuffling.*.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open.

6. Click Import, then click Close to close the Import tab.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter oht_opti_ph3.hm for the file name and save it to your working directory.

Updating the Design Variables 1. In the optimization panel, click the composite shuffle panel. 2. Click review. 3. Select free-size to review the design variable. 4. Select the parameters subpanel. 5. Click edit. The DSHUFFLE card opens. 6. Select MAXSUCC and in the MSUCC field, enter 4.

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7. Select COVER and in the NUMBER_OF_VANG field, enter 4. 8. In the DSHUFFLE card editor, edit the card. a) In the VREP field, enter 1.

b) In the VANG(1) field, enter -45. c) In the VANG(2) field, enter 0.

d) In the VANG(3) field, enter 45. e) In the VANG(4) field, enter 90.

This sets the outermost layer of the shuffling sequence to maintain one repetition of a set of -45, 0, 45, 90 degree plies. This ply set is applied to both faces of this optimization, since the laminate is symmetric. 9. Click return to exit the editor. 10. Click update to update the design variable. 11. Click return to return to the optimization page.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter oht_opti_ph3 for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file oht_opti_ph3.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: oht_opti_ph3.prop OptiStruct property output file containing all updated property data from the last iteration for size optimization.

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oht_opti_ph3.shuf.html An HTML file contains the history of the shuffling optimization and the view of the ply stacking sequence.

Post-processing Results In an Internet browser, open the oht_opti_ph3.shuf.html file. The plies are color coded based on their fiber orientations. The columns represent the global trend of the ply stacking sequence at a particular iteration, with the last column being the final solution. The weight of the part has not been changed during the shuffling design phase, rather the plies were reordered to obtain the maximum performance. This light weight design therefore meets all of the performance requirements, is feasible and manufacturable.

Figure 713: Shuffling Optimization History

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Performing a Final Post-Optimization Analysis Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the oht_opti_ph3.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Model Importing Final Optimization Properties 1. In the Import Browser, File field, browser for the oht_opti_ph3.prop file. 2. Under Import options, select FE overwrite. 3. Click Import. The properties of the model are updated with the optimized parameters.

Editing the Contol Cards 1. In the Model Browser, expand the Cards folder. 2. Delete the OMIT card. a) Right-click on OMIT and select Delete from the context menu. b) HyperMesh asks you to confirm the delete. Click Yes to continue. 3. Edit the OUTPUT card.

a) Click the OUTPUT card. b) In the Entity Editor, in the number_of_outputs field, enter 2.

The final section of the card is deleted.

Deleting the Optimization Entities 1. In the Model Browser, right-click on the Design Variables folder and select Delete from the context menu.

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2. Click Yes to continue. 3. In the Model Browser, right-click on the Optimization Responses folder and select Delete from the context menu. 4. Click Yes to continue.

Reviewing the Model In this step you will change the settings on the Visualization toolbar to update the appearance of the model. 1. Set the element visualization model to 2D detailed element representation. This will thicken all shells in the model to their total thickness, displaying them as 3-dimensional representations of their thicknesses. 2. Set Layers to Composite Layers. This will separate the view into individual plies. 3. Set the element color mode to By Prop. This will assist you in determining which plies are which in the layup. This represents each of the plies in the model according to the color of its ply as shown in the Model Browser. If all of the plies in the model are the same color, change the ply colors in the Model Browser so that each is different to help differentiate the plies in the graphics area.

Figure 714: Model Thickness with Half of the Model's Elements Masked

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Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 715: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter oht_final for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the oht_final.fem was written. The oht_final.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results 1. From the OptiStruct panel, click HyperView. HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView. 2. On the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Composites Strains(Mech) (s) and the subtype to Normal X Strain. This corresponds to the fiber strain in the model. 4. To view the individual strain contributions from any one ply, select the appropriate ply name in the Layers drop-down. Confirm that no ply exceeds 9000 microstrain (9e-3). 5. Set the Result type to Composites Strains(Mech) (s) and the subtype to Normal Y Strain. This corresponds to the matrix strain value.

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6. To view the individual strain contributions from any one ply, select the appropriate ply name in the Layers drop-down. Confirm that no ply exceeds 7000 microstrain (9e-3) for the matrix. The final design weighs ~0.33 lbs.

Figure 716: Maximum Normal Y Strain Across all Plies No element exceed 0.007 me.

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Size Optimization Size Optimization

This chapter covers the following: •

OS-T: 4000 3D Size Optimization of a Rail Joint (p. 779)

•

OS-T: 4010 Size Optimization of a Welded Bracket (p. 788)

•

OS-T: 4020 Composite Bike Frame Optimization (p. 796)

•

OS-T: 4030 Discrete Size Optimization of a Welded Bracket (p. 806)

•

OS-T: 4040 Size Optimization of a Shredder (p. 814)

•

OS-T: 4050 Optimization of a Horizontal Tail Plane (p. 827)

•

OS-T: 4070 Free-sizing Nonlinear Gap Optimization on an Airplane Wing Rib (p. 856)

•

OS-T: 4080 Minimization of the Maximum Stress of a Rotating Bar (p. 865)

•

OS-T: 4090 Manufacturing Constraints of a Composite Structure (p. 872)

•

OS-T: 4095 Size Optimization using External Responses (DRESP3) (p. 883)

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OS-T: 4000 3D Size Optimization of a Rail Joint In this tutorial you will perform a size optimization on an automobile rail joint modeled with shell elements. A structural model with loads and constraints is used in this tutorial. The deflection at the end of the tubular cross-member should be limited. The optimal solution would be to use as little material as possible.

Figure 717: Structural Model of a Rail Joint

You will load the structural model into HyperMesh. The constraints, loads, material properties, and subcases (loadsteps) are already defined in the model. Size design variables and optimization parameters are defined, and OptiStruct determines the optimal gauges for the components. The results are then reviewed in HyperView. The optimization problem for this tutorial is stated as: Objective

Minimize volume.

Constraints

A given maximum nodal displacement at the loading grid point for two loading conditions.

Design Variables

Gauges of the two parts.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the joint_size.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The joint_size.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Size Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the size panel. 3. Select the desvar subpanel. 4. Create the design variable, tube. a) In the desvar = field, enter tube.

b) In the initial value = field, enter 1.0.

c) In the lower bound = field, enter 0.1.

d) In the upper bound = field, enter 5.0.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. 5. Create the design variable, rail. a) In the desvar = field, enter rail.

b) In the initial value = field, enter 1.0.

c) In the lower bound = field, enter 0.1.

d) In the upper bound = field, enter 5.0.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. 6. Select the generic relationship subpanel. 7. Create a design variable property relationship, tube_th. a) In the name = field, enter tube_th.

b) Using the prop selector, select tube2. c) Under the props selector, select Thickness T. d) Click designvars.

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e) Select tube. Notice: The linear factor is automatically set to 1.000. f) Click return. g) Click create. A design variable property relationship, tube_th, has been created relating the design variable tube to the thickness entry on the PSHELL card for the property tube2.

8. Create a design variable property relationship, rail_th. a) In the name = field, enter rail_th.

b) Using the prop selector, select tube1. c) Under the props selector, select Thickness T. d) Click designvars. e) Select rail. f) Click return. g) Click create. A design variable property relationship, rail_th, has been created relating the design variable rail to the thickness entry on the PSHELL card for the property tube1.

9. Click return to go to the Optimization panel.

Creating Responses 1. Click the responses panel. 2. Create the response, volume. a) In the response= field, enter volume. b) Set the response type to volume.

c) Set the regional selection to total. d) Click create. The response, volume, is defined for the total volume of the model. 3. Create the response, X_Disp. a) In the response= field, enter X_Disp.

b) Set the response type to static displacement. c) Click nodes > by id, then enter 3143 in the id= field.

This is the node at center of rigid spider at loading point.

d) Select dof1. e) Click create. The response, X_Disp, is defined for the x-displacement of the node 3143. 4. Create the response, Z_Disp. a) In the response= field, enter Z_Disp.

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OptiStruct Tutorials Size Optimization b) Set the response type to static displacement. c) Click nodes > by id, then enter 3143 in the id= field.

This is the node at center of rigid spider at loading point.

d) Select dof3. e) Click create. The response, Z_Disp, is defined for the z-displacement of the node 3143. 5. Click return to go to the Optimization panel.

Creating Constraints A response defined as the objective cannot be constrained. In this case, you cannot constrain the response volume. Upper bound constraints are to be defined for the responses X_Disp and Z_Disp. 1. Click the dconstraints subpanel. 2. Define a constraint on the response X_Disp. a) In the constraints= field, enter Disp_X.

b) Check the box next to upper bound, then enter 0.9. c) Click response = and select X_Disp.

d) Using the loadsteps selector, select Force_X. e) Click create. The constraint is an upper bound with a value of 0.9. The constraint applies to the subcase Force_X. 3. Define a constraint on the response Z_Disp. a) In the constraints= field, enter Disp_Z.

b) Check the box next to upper bound, then enter 1.6. c) Click response = and select Z_Disp.

d) Using the loadsteps selector, select Force_Z. e) Click create. The constraint is an upper bound with a value of 1.6. The constraint applies to the subcase Force_Z. 4. Click return to go to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

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Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter joint_sizeOPT.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter joint_sizeOPT for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file joint_sizeOPT.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: joint_sizeOPT.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. joint_sizeOPT.prop OptiStruct property output file containing all updated property data from the last iteration for size optimization. joint_sizeOPT.hist The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history. joint_sizeOPT.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the joint_sizeOPT.fem file.

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joint_sizeOPT.res HyperMesh binary results file. joint_sizeOPT.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. joint_sizeOPT_des.h3d HyperView binary results file that contain optimization results. joint_sizeOPT_s#.h3d HyperView binary results file that contains from linear static analysis, and so on.

Viewing the Results Displacement and stress results are output by OptiStruct (by default) for linear static analyses. You will view those results in HyperView. Size optimization results from OptiStruct are given in the .h3d files and joint_sizeOPT.out. joint_sizeOPT_des.h3d Contains the element thickness for all five iterations. joint_sizeOPT_s1.h3d Contains displacement and stress results for the linear static analysis for iteration 0 and iteration 4 of subcase with ID 1 (subcase Force_X). joint_sizeOPT_s2.h3d Contains displacement and stress results for the linear static analysis for iteration 0 and iteration 4 of subcase with ID 2 (subcase Force_Z). joint_sizeOPT.out Contains gauge and volume information for all iterations. The results contained in the HyperView binary results file will be examined first. Then the gauge history in the joint_sizeOPT.out file will be reviewed.

Viewing the Size Optimization Results 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads the result files. All three .h3d files get loaded into a different page in HyperView. The files joint_sizeOPT_des.h3d, joint_sizeOPT_s1.h3d, and joint_sizeOPT_s2.h3d get loaded in page 2, page 3, and page 4, respectively. The optimization iteration results (gauge thickness) are loaded in the first page. The name of the page is displayed as Design History to indicate that the results correspond to optimization iterations. 2. On the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Element Thicknesses (s) and Thickness. 4. Set the Averaging method to None.

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5. In the Results Browser, select the last load case simulation. 6. In the Contour panel, click Apply. A contoured image representing shell thickness should be visible. Each element in the model is assigned a legend color, indicating the thickness value for that element for the current iteration.

Figure 718: Thickness Contour at Last Iteration

Viewing the Displacement Results It is helpful to view the deformations of the model to determine if the boundary conditions have been met and also to see if the model is deforming as expected. These analysis results are available in pages 3 and 4. 1. In the top, right of the application, click

to proceed to third page.

The third page, which has results loaded from the file joint_sizeOPT_s1.h3d, is displayed. The name of the page is displayed as Subcase 1 - FORCE_X to indicate that the results correspond to subcase 1. 2. From the Animation toolbar, set the animation mode to Linear Static. 3. On the Results toolbar, click

to open Contour panel.

4. Set the Result type to Displacement [v] and X. 5. Click Apply. The resulting contours represent the x component displacement field resulting from the applied loads and boundary conditions. 6. Measure the displacement at node 3143 for which you have constrained the displacement. a) On the Annotations toolbar, click

to open the Measure panel.

b) Click Add to add a new measure group. c) Select Nodal Contour. d) Click Nodes > by id, then enter 3143 in the Node ID field and click OK.

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The x-displacement value for 3143 (center of rigid spider, where loading is applied) displays. The x-displacement is larger than the upper bound constraint, which was defined earlier, of 0.9.

Figure 719: Displacement on X-direction for the X-force loadcase at the first iteration

7. In the Results Browser, select the last iteration. The contour now shows the x-displacement results for Subcase 1 (FORCE_X) and iteration 4, which corresponds to the end of the optimization iterations. The x-displacement is now less than 0.9.

Figure 720: Displacement on X-direction for the X-force loadcase at the last iteration

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8. In the top, right of the application, click

to proceed to fourth page.

The fourth page shows the results loaded from the joint_sizeOPT_s2.h3d file. The name of the page is displayed as Subcase 2 - Force_Z to indicate that the results correspond to subcase 2. 9. On the Results toolbar, click

to open the Contour panel.

10. Set the Result type to Displacement [v] and Z. 11. Click Apply. The resulting contours represent the z component displacement field resulting from the applied loads and boundary conditions. 12. Measure and display the z-displacement value for node 3143.

Figure 721:

Viewing the Gauge Thickness Results In this step you will learn an alternate way to view the gauge thickness results. 1. From the Unix or MSDOS shell, open the joint_sizeOPT.out file in a text editor.

2. Review all five iterations, noting the volume, constraint information, and gauge at each iteration. Has the volume been minimized for the given constraints? Have the displacement constraints been met? What are the resulting gauges for the rail and tube?

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OS-T: 4010 Size Optimization of a Welded Bracket In this tutorial you will perform a size optimization on a welded bracket modeled with shell elements. A structural model with loads and constraints is used in this tutorial. The objective is to minimize the amount of material used in the model subject to certain stress specifications. The gauge changes of the bracket are linked to each other so that the gauge is identical for both sides at the optimal design.

Figure 722: Structural Model of the Welded Bracket

You will load the structural model into HyperMesh. The constraints, loads, material properties, and subcases (loadsteps) are already defined in the model. Size design variables and optimization parameters are defined and the OptiStruct software determines the optimal gauges. The results are then reviewed in HyperMesh. The optimization problem is stated as: Objective

Minimize volume.

Constraints

Maximum von Mises Stress of the brackets < 100 Mpa.

Design Variables

Gauges of the brackets.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the bracket_size.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The bracket_size.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Size Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the size panel. 3. Select the desvar subpanel. 4. Create the design variable, part1. a) In the desvar = field, enter part1.

b) In the initial value = field, enter 2.5.

c) In the lower bound = field, enter 1.0.

d) In the upper bound = field, enter 2.5.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. 5. Create the design variable, part2. a) In the desvar = field, enter part2.

b) In the initial value = field, enter 2.5.

c) In the lower bound = field, enter 1.0.

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d) In the upper bound = field, enter 2.5.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. 6. Select the generic relationship subpanel. 7. Create a design variable property relationship, part1_th. a) In the name = field, enter part1_th.

b) Using the prop selector, select part1. c) Under the props selector, select Thickness T. d) Click designvars. e) Select part1. Notice: The linear factor is automatically set to 1.000. f) Click return. g) Click create. A design variable property relationship, part1_th, has been created relating the design variable part1 to the thickness entry on the PSHELL card for the property part1.

8. Create a design variable property relationship, part2_th. a) In the name = field, enter part2_th.

b) Using the prop selector, select part2. c) Under the props selector, select Thickness T. d) Click designvars. e) Select part2. f) Click return. g) Click create. A design variable property relationship, part2_th, has been created relating the design variable part2 to the thickness entry on the PSHELL card for the property part2.

9. Click return to go to the Optimization panel.

Linking Design Variables 1. Click the desvar link panel. 2. In the dlink = field, enter link1.

3. Under dependent, click designvar= and select part2. 4. Under independent, click designvars and select part1. Notice: The linear factor is automatically set to 1.000. 5. Click return.

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6. In the C0 = field, enter 0.000.

7. In the CMULT = field, enter 1.000. 8. Click create.

9. Click return to go to the Optimization Setup panel. The design variable part2 is now linearly dependent on the design variable part1.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter volume. b) Below response type, select volume.

c) Set regional selection to total and no regionid. d) Click create. 4. Create a static stress response. a) In the response= field, enter stress1.

b) Set the response type to static stress. c) Using the props selector, select part1. d) Set the response selector to von mises. e) Under von mises, select both surfaces. f) Click create. 5. Create another static stress response named stress2, which is defined for the von Mises stress of the elements in the component part2. 6. Click return to go back to the Optimization panel.

Creating Constraints A response defined as the objective cannot be constrained. In this case, you cannot constrain the response volume. Upper bound constraints are to be defined for the responses stress1 and stress2. 1. Click the dconstraints subpanel. 2. Define a constraint on the response stress1. a) In the constraints= field, enter stress1.

b) Check the box next to upper bound, then enter 100. c) Click response = and select stress1.

d) Using the loadsteps selector, select STEP. e) Click create.

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The constraint is an upper bound with a value of 100. The constraint applies to the subcase STEP. 3. Define a constraint on the response stress2. a) In the constraints= field, enter stress2.

b) Check the box next to upper bound, then enter 100. c) Click response = and select stress2.

d) Using the loadsteps selector, select STEP. e) Click create. The constraint is an upper bound with a value of 100. The constraint applies to the subcase STEP. 4. Click return to go to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter bracket_size.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter bracket_size for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED.

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FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file bracket_size.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: bracket_size.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. bracket_size.prop OptiStruct property output file containing all updated property data from the last iteration for size optimization. bracket_size.hist_dat OptiStruct iteration history file, containing the iteration history of the objective function and of the most violated constraint. Can be used for an xy plot of the iteration history. bracket_size.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. bracket_size.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the bracket_size.fem file. bracket_size.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. bracket_size.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. bracket_size.h3d HyperView binary results file.

Viewing the Results Size optimization results from OptiStruct are given in two places. The bracket_size.out file contains gauge and volume information for all iterations. The bracket_size.h3d file contains the element thickness for all five iterations and Displacement and Stress results for the linear static analysis for iteration 0 and iteration 3. In this step you will review all results. The results contained in the HyperMesh binary results file will be examined first. The gauge history in the bracket_size.out file will then be reviewed.

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Viewing the Stress Results After the size optimization, the stress value should be reviewed to make sure the stress constraints are not violated. 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads the result files. All of the .h3d files get loaded into a different page in HyperView. The files bracket_size_des.h3d and bracket_size_s1.h3d get loaded in page 2 and page 3, respectively. 2. In the top, right of the application, click

to proceed to the next page.

The third page has the results loaded from the bracket_size_s1.h3d file. The name of the page is displayed as Subcase 1 - STEP to indicate that the results correspond to subcase 1. 3. On the Results toolbar, click

to open the Contour panel.

4. Set the Result type to Element Stresses [2D & 3D] (t) and vonMises. 5. Set the Averaging method to None. 6. Click Apply. A contoured image representing von Mises stresses should be visible. Each element in the model is assigned a legend color, indicating the von Mises stress value for that element resulting from the applied loads and boundary conditions. If you did not change the Iteration step, you should contour the stress of the initial step. To contour the final step, set the last iteration of that loadcase using the Model Browser. 7. In the Results Browser, select the last iteration from the simulation list. Only two iterations are displayed; the First and Last (FL) is the default setting for optimization runs. To change this setting, add an OUTPUT control card with a frequency setting of ALL.

Figure 723:

This will now contour your final iteration of that loadcase. Review the stress to see that it is under the proper constraints.

Viewing the Thickness Results

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p.795 to go back to the previous page.

2. Set the Result type to Element Thicknesses (s). 3. In the Results Browser, select Iteration 2 from the Load Case and Simulation Selection. 4. Click Apply. Alternatively, you can also open the bracket_size.prop file in a text editor to view the final gauge thicknesses of the two parts.

Reviewing the .out File The .out file contains a summary of the optimization process. From the information in the .out file, you can see how the objective, constraints, and design variables are changing from one iteration, to the next. Has the volume been minimized for the given constraints? Have the stress constraints been met? What are the resulting gauges for the two parts? Did the design variable linking work?

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OS-T: 4020 Composite Bike Frame Optimization In this tutorial you will perform a ply orientation optimization for a composite structure.

Figure 724: Bicycle Frame Model

The optimization problem for this tutorial is stated as: Objective

Minimize volume.

Constraints

A given maximum nodal displacement.

Design Variables

Layer thickness.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the bicycle_frame.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The bicycle_frame.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Load Collectors 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. For Name, enter crank.

3. Click Color and select a color from the color palette. 4. Set Card Image to None. 5. Create another load collector. a) For Name, enter spcs.

b) For Card Image, select None.

Creating Loads 1. In the Model Browser, Load Collectors folder, right-click on crank and select Make Current from the context menu. 2. Create a force. a) From the Analysis page, click the forces panel. b) Select the create subpanel. c) Set the entity selector to nodes, then select the node at the center of the rigid spider. d) Set the coordinate system toggle to global system. e) In the magnitude = field, enter -100.0. f) Set the direction definition to z-axis. g) Click create. h) Click return. A point force is created at the pedal location. 3. Create a moment. a) From the Analysis page, click the moments panel.

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b) Select the create subpanel. c) Set the entity selector to nodes, then select the node at the center of the rigid spider. d) Set the coordinate system toggle to global system. e) In the magnitude = field, enter 100.0. f) Set the direction definition to x-axis. g) Click create. h) Click return. A moment is created at the pedal location. Note: This is a simplified loading regime that represents the transformed loads from a person's foot on the pedal.20.

Figure 725: Loads applied to bottom bracket of a bicycle

Creating Constrains 1. In the Model Browser, Load Collectors folder, right-click on spcs and select Make Current from the context menu. 2. From the Analysis page, click the constraints panel. 3. Select the create subpanel. 4. Set the entity selector to nodes, then select the nodes to constrain the structure by clicking on the center of the rigid spiders.

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Figure 726: SPCs Applied to Rear Wheel Location of Frame

Figure 727: SPCs Applied to Upper and Lower Portion of Head Tube

5. Constrain all dofs.

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Dofs with a check are to be constrained, while dofs without a check will be free. Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom. Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom. 6. Click create. 7. Click return. Constraints are applied to the selected nodes.

Creating Load Steps 1. In the Model Browser, right-click and select Create > Load Step from the context menu. A default load step displays in the Entity Editor. 2. For Name, enter crank.

3. Set Analysis type to linear static. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select spcs and click OK. 5. Define LOAD. a) For LOAD, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select crank and click OK.

Creating Design Variables 1. From the 2D page, click the HyperLaminate panel. HyperLaminate opens. 2. Create the design variable, thk1. a) In the Laminate Browser, expand Design Variable, right-click on DESVAR, and select New from the context menu. A new design variable, named NewDv1 by default, is added. b) In the Desvar field, enter thk1.

c) In the Initial value field, enter 1.0.

d) In the Lower bound field, enter 0.0. e) In the Upper bound field, enter 2.0. f) Click Apply.

3. Create four more design variables named thk2, thk3, thk4, and thk5 using the same values as thk1. Tip: Quickly create identical design variables by right-clicking on thk1 and selecting Duplicate from the context menu. 4. Examine the PCOMP branch to see all of the PCOMPs in the model.

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5. Select the seat_tube PCOMP. Details of the laminate appear. 6. Click the check box next to Optimization at the top of the middle panel. New fields appear in the Ply lay-up order table allowing design variables to be associated to ply thicknesses or ply orientations. 7. In the Ply lay-up order table, row 1, set Thickness Designvar to thk1. 8. Change the Thickness Designvar for the other rows as shown in Figure 728.

Figure 728:

9. Click Update Laminate. The design variables thk(i) are now associated with the thickness for the ply(i) of this laminate. In this case, ply(11-i) too, since this is a symmetric laminate. 10. Repeat this process for TOP_tube and down_tube using the same DVs as on the seat_tube property. 11. From the menu bar, click File > Exit.

Setting Up the Optimization Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter volume. b) Below response type, select volume.

c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter disp.

b) Below response type, select static displacement.

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c) Using the nodes selector, select the node at the bottom of the bracket where the loads were applied. d) Set the displacement type to total disp. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

e) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter Disp. 3. Click response = and select disp.

4. Check the box next to upper bound, then enter 1.8. 5. Using the loadsteps selector, select crank. 6. Click create. 7. Click return to go back to the Optimization panel. A constraint is defined on the response disp. It states that any solution (min. volume) needs to have a displacement lower than 1.8 mm to be feasible.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as.

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3. In the Save As dialog, specify location to write the OptiStruct model file and enter bicycle_frameOPT for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file bicycle_frameOPT.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results In this step you will view the design variable and objective history. 1. From the Page Controls toolbar, click

to open a session of HyperView.

2. From the menu bar, click File > Open > Session. 3. In the Open Session File dialog, navigate to your working directory and open the bicycle_frameOPT_hist.mvw file. This file contains plots of the objective, constraints, and design variables against iteration history. The first page shows the objective function.

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Figure 729: Objective function (Volume) for each iteration

The second page shows the maximum constraint violation.

Figure 730: Maximum constraint violation (% [disp > 1.8 mm]) for each iteration

The next pages show the design variables (DVs) which are grouped together making it possible to compare the behavior of the different plies. This plot can be created by opening the bicycle_frameOPT.hgdata file.

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OptiStruct Tutorials Size Optimization

Figure 731: Design variable values for each iteration

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OS-T: 4030 Discrete Size Optimization of a Welded Bracket In this tutorial you will perform a size optimization on a welded bracket modeled with shell elements using discrete design variables. A structural model with loads and constraints is used in this tutorial. The objective is to minimize the amount of material used in the model subject to certain stress specifications.

Figure 732:

You will load the structural model into HyperMesh. The constraints, loads, material properties, and subcases (loadsteps) are already defined in the model. Size design variables and optimization parameters are defined, and OptiStruct determines the optimal gauges. The results are then reviewed in HyperView. The optimization problem is stated as: Objective

Minimize volume.

Constraints

Maximum von Mises stress of the brackets < 120 MPa.

Design Variables

Gauges of the brackets.

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the bracket_size.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The bracket_size.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Discrete Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the discrete dvs panel. 3. Create the discrete design variable, DDV1. a) In the name= field, enter DDV1. b) In the from= field, enter 0.5. c) In the to= field, enter 3.0.

d) In the increment= field, enter 0.1. e) Click create.

A discrete design variable is created with a starting value of 0.5 and ending value of 3.0. The variables are incremented by 0.1, making the possible values as 0.5, 0.6, 0.7, and so on until 3.0. 4. Create the discrete design variable, DDV2, with the same discrete values as DDV1. 5. Click return to go back to the optimization panel.

Creating Size Design Variables 1. From the Analysis page, click the optimization panel.

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2. Click the size panel. 3. Select the desvar subpanel. 4. Create the design variable, part1. a) In the desvar = field, enter part1.

b) In the initial value = field, enter 2.5.

c) In the lower bound = field, enter 0.5.

d) In the upper bound = field, enter 3.0.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to ddval=, then click ddval and select DDV1. This links the design variable to the DDVAL (Discrete Design Variable Value) DDV1. g) Click create. 5. Create the design variable, part2. a) In the desvar = field, enter part2.

b) In the initial value = field, enter 2.5.

c) In the lower bound = field, enter 0.5.

d) In the upper bound = field, enter 3.0.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to ddval=, then click ddval and select DDV2. g) Click create. 6. Select the generic relationship subpanel. 7. Create a design variable property relationship, part1_th. a) In the name = field, enter part1_th.

b) Using the prop selector, select part1. c) Under the props selector, select Thickness T. d) Click designvars. e) Select part1. Notice: The linear factor is automatically set to 1.000. f) Click return. g) Click create. A design variable property relationship, part1_th, has been created relating the design variable part1 to the thickness entry on the PSHELL card for the property part1.

8. Create a design variable property relationship, part2_th. a) In the name = field, enter part2_th.

b) Using the prop selector, select part2. c) Under the props selector, select Thickness T. d) Click designvars. e) Select part2. f) Click return.

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g) Click create. A design variable property relationship, part2_th, has been created relating the design variable part2 to the thickness entry on the PSHELL card for the property part2.

9. Click return to go to the Optimization panel.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter volume. b) Below response type, select volume.

c) Set regional selection to total and no regionid. d) Click create. 4. Create a static stress response. a) In the response= field, enter stress1.

b) Set the response type to static stress. c) Using the props selector, select part1. d) Set the response selector to von mises. e) Under von mises, select both surfaces. f) Click create. 5. Create another static stress response named stress2, which is defined for the von Mises stress of the elements in the component part2. 6. Click return to go back to the Optimization panel.

Creating Constraints A response defined as the objective cannot be constrained. In this case, you cannot constrain the response volume. Upper bound constraints are to be defined for the responses stress1 and stress2. 1. Click the dconstraints subpanel. 2. Define a constraint on the response stress1. a) In the constraints= field, enter stress1.

b) Check the box next to upper bound, then enter 100. c) Click response = and select stress1.

d) Using the loadsteps selector, select STEP. e) Click create. The constraint is an upper bound with a value of 100. The constraint applies to the subcase STEP.

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3. Define a constraint on the response stress2. a) In the constraints= field, enter stress2.

b) Check the box next to upper bound, then enter 120. c) Click response = and select stress2.

d) Using the loadsteps selector, select STEP. e) Click create. The constraint is an upper bound with a value of 120. The constraint applies to the subcase STEP. 4. Click return to go to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select volume. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter discrete_bracket_size for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file discrete_bracket_size.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

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Viewing the Results After the size optimization, the stress value should be reviewed to make sure that the stress constraints are not violated. The analysis results are available on page 3 (the second page has the optimization results). 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads the result files. All of the .h3d files get loaded into a different page in HyperView. The files discrete_bracket_size_des.h3d and discrete_bracket_size_s2.h3d get loaded in page 2 and page 3, respectively. 2. Click the Next Pagetoolbar icon

to move to the third page.

The third page has the results loaded from the discrete_bracket_size_s1.h3d file. The name of the page is displayed as Subcase 1 - STEP to indicate that the results correspond to subcase 1. 3. On the Results toolbar, click

to open the Contour panel.

4. Set the Result type to Element Stresses [2D & 3D] (t) and vonMises. 5. Set the Averaging method to None. 6. Click Apply. A contoured image representing von Mises stresses should be visible. Each element in the model is assigned a legend color, indicating the von Mises stress value for that element resulting from the applied loads and boundary conditions. If you did not change the Iteration step you should be contouring the stress of the initial step.

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Figure 733: von Mises contour for the initial design

7. On the Animation toolbar, click

to set the last iteration of that loadcase and contour the final

step. Only two iterations are displayed; the First and Last (FL) is the default setting for optimization runs. To change this setting, add an OUTPUT control card with a frequency setting of ALL. This will now contour your final iteration of that loadcase. Review the stress to see that it is under the proper constraints.

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Figure 734:

Review The .out file contains a summary of the optimization process. From the information in the.out file, you can see how the objective, constraints, and design variables are changing from one iteration to the next. Has the volume been minimized for the given constraints? Have the stress constraints been met? What are the resulting gauges for the two parts? Hints Go to the des.h3d page, clear the contour if one was applied, set to the last simulation step and apply the Element Thickness contour. Append discrete_bracket_size.mvw to review objective, constraints, and other information.

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OS-T: 4040 Size Optimization of a Shredder In this tutorial you will perform a size optimization for a model comprised of shell and bar elements. You will update the PBARL property to simulate the properties of the bar elements and then link that to the design variable. The resulting design will have higher frequencies and updated element properties. Size optimizations involve the changing of the properties of either 1D or 2D elements. These properties include area, moments of inertia of the 1D elements, and the thickness of 2D elements. Size optimization is performed when it is not necessary to remove materials, generate beads or change the shape of the structure. With size optimization, the cross-sectional properties of the elements are changed to meet the necessary objective. Properties are linked with design variables (DESVAR) using DVPREL cards. This tutorial outlines using OptiStruct macros under an OptiStruct user profile to setup the optimization problem.

Figure 735: Finite Element Model of a Shredder

The optimization problem is stated as: Objective

Minimize the global mass.

Constraints

Transverse modes higher than 6 Hz.

Design Variables

Beam width, beam thickness, beam depth, and shell thickness.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears.

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2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the shredder.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Performing Finite Element Analysis and Checking Results Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 736: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter shredder_analysis for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save.

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The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the shredder_analysis.fem was written. The shredder_analysis.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Eigen Modes 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and a new page and session file, shredder_analysis.mvw, loads. This file is linked with the shredder_analysis.h3d file, which contains the model and results. 2. On the Animation toolbar, set the animation type to 3. On the Results toolbar, click

(Modal).

to open the Deformed panel.

4. Define deformed shape settings. a) Set the Result type to Eigen Mode(v). b) Set Scale to Model Units. c) Set Type to Uniform. d) In the Value field, enter 1000. This means that the maximum displacement will be 1000 modal units and all other displacements will be proportional. Using a scale factor higher than 1.0, amplifies the deformations while a scale factor smaller than 1.0 would reduce them. In this case, you are accentuating displacements in all directions. 5. Define undefomed shape settings. a) Set Show to Edges. b) Set Color to Mesh. 6. Click Apply. 7. In the Results Browser, from the list of simulations, select Mode 1.

Figure 737:

8. On the Results toolbar, click

to open the Contour panel.

9. Click Apply.

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The Eigen Mode contour is plotted. 10. On the Annotations toolbar, click

to open the Note panel.

11. In the Description pane, remove the first two lines.

Figure 738:

12. Click Apply. 13. On the Page Controls toolbar, set the page layout to

.

Figure 739:

14. Click the first window, then click Edit > Copy > Window from the menu bar. 15. Click the second window, then click Edit > Paste > Window from the menu bar. 16. Copy the first window into the third and fourth windows.

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Figure 740: First mode on contour on all windows

17. Change the mode assigned to the windows by clicking a window to make it active, then selecting a mode in the Results Browser. • Set the second window to Mode 2. • Set the third window to Mode 3. • Set the fourth window to Mode 4.

Figure 741:

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Figure 742: First Four Eigen Modes Contour

18. On the Animation toolbar, click

to start the animation. Click again to stop the animation.

The third and fourth mode (~ 3.9 and 4.8 Hz) has a transversal shape that can reduce the performance of the shredder when it gets excited. The objective, then, is to get the minimum mass to greater than 7Hz. 19. From the menu bar, click File > Save As > Report Template. 20. In the Save Report As dialog, navigate to your working directory and save the file as report.tpl.

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Figure 743:

21. In the top, right of the application, click

and

to navigate back to the HyperMesh client on

the first page.

Setting Up the Optimization Defining Design Variables The design variables for this problem are the thickness of the cover, width, thickness, and depth of the bar. You will define the first design variable using the Size panel. 1. From the Analysis page, click the optimization panel. 2. Click the size panel. 3. Select the desvar subpanel. 4. Create the design variable, coverthck. a) In the desvar = field, enter coverthck. b) In the initial value = field, enter 3.0.

c) In the lower bound = field, enter 1.0.

d) In the upper bound = field, enter 6.0.

e) Set the move limit toggle to move limit default.

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f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. 5. Create four more design variables. Design Variable

Initial Value

Lower Bound

Upper Bound

Beamwide

50

30

90

Beamhigh

100

80

125

Beamthck1

10

5

15

Beamthck2

20

15

30

6. Select the generic relationship subpanel. 7. Create a design variable property relationship, coverthck. a) In the name = field, enter coverthck. b) In the C0 field, enter 0.0.

c) Using the prop selector, select cover. d) Under the props selector, select Thickness T. e) Click designvars, select coverthck, and click return. f) Click create. In the next steps you will define property relations for beam dimensions. Each dimension of a C beam will be defined as a design variable.

Figure 744:

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Table 2: Property Values on the Initial Design

Name

Represents

Value

DIMs(1)

Beam Width

50

DIMs(2)

Beam High

100

DIMs(3)

Beam Thck1

10

DIMs(4)

Beam Thck2

20

8. Create a design variable property relationship, DIM1. a) In the name = field, enter DIM1. b) In the C0 field, enter 0.0.

c) Using the prop selector, select frame2. d) Under the props selector, select Dimension 1. e) Click designvars, select Beamwide, and click return. f) Click create. 9. Create a design variable property relationship, DIM2. a) In the name = field, enter DIM2. b) In the C0 field, enter 0.0.

c) Using the prop selector, select frame2. d) Under the props selector, select Dimension 2. e) Click designvars, select Beamhigh, and click return. f) Click create. 10. Create a design variable property relationship, DIM3. a) In the name = field, enter DIM3. b) In the C0 field, enter 0.0.

c) Using the prop selector, select frame2. d) Under the props selector, select Dimension 3. e) Click designvars, select Beamthck1, and click return. f) Click create. 11. Create a design variable property relationship, DIM4. a) In the name = field, enter DIM4. b) In the C0 field, enter 0.0.

c) Using the prop selector, select frame2. d) Under the props selector, select Dimension 4. e) Click designvars, select Beamthck2, and click return. f) Click create. 12. Click return to go back to the Optimization panel.

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Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the mass response, which is defined for the total volume of the model. a) In the responses= field, enter mass. b) Below response type, select mass.

c) Set regional selection to total and no regionid. d) Click create. 4. Create the frequency response. a) In the responses= field, enter f3.

b) Below response type, select frequency. c) For Mode Number, enter 3. d) Click create.

A response, f3, is defined for the frequency of the third mode extracted. 5. Create another frequency response, named f4, for mode 4. 6. Click return to go back to the Optimization panel.

Defining Constraints 1. Click the dconstraints panel. 2. Create the constraint, c_f3. a) In the constraint= field, enter c_f3.

b) Check the box next to lower bound, then enter 6.0. c) Click response = and select f3.

d) Using the loadsteps selector, select ld1. e) Click create. 3. Create the constraint, c_f4. a) In the constraint= field, enter c_f4.

b) Check the box next to lower bound, then enter 6.0. c) Click response = and select f4.

d) Using the loadsteps selector, select ld1. e) Click create. 4. Click return to exit the panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected.

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3. Click response and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter shredder_optimization.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter shredder_optimization for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file shredder_optimization.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and the results are loaded. 2. In the top, right of the application, click

and

3. In the Results Browser, select the last iteration.

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Figure 745:

4. On the Results toolbar, click

to open the Contour panel.

5. Set the Result type to Element Thicknesses (s) and Thickness. 6. Click Apply. The resulting colors represent the thickness fields resulting from the applied loads and boundary conditions. The final optimized thickness of the cover component is 1.0. 7. Open the shredder_optimization.prop file using any text editor to review final optimized PBAR property.

Figure 746:

The final dimensions could be rounded off to: Beam Wide (DIM1)

70.10

Beam High (DIM2)

125

Beam Thck (DIM3)

5

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This .prop file can be read into HyperMesh with over write mode on and the PBARL card will be updated.

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OS-T: 4050 Optimization of a Horizontal Tail Plane In this tutorial you will optimize the thickness of the aluminum ribs for a horizontal tail plane.

Figure 747: Horizontal Tail Plane Model

It is assumed that the tail is cantilevered about its inboard section. Three loading scenarios are considered; one where the tail experiences pressure loads of 0.25 psi on the bottom skin, a second where the tail experiences a tip load of 400 lbs, and a third where the tail experiences both the pressure load and tip load simultaneously. The applied loading is represented below.

Figure 748: Loading Experienced by Horizontal Tail Plane

The optimum design should be as light as possible without failing or buckling under the given loading conditions.

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Table 3: Part Materials

Glass_fabric

Core

Aluminum 2024-T3

E1

4Msi (4.0e6 psi)

2ksi (2000 psi)

E

10.6Msi (10.6e6 psi)

E2

6Msi (6.0e6 psi)

4ksi (4000 psi)

Nu

0.33

NU12

0.1

0.3

G

4.06Msi (4.06e6 psi)

G12

800ksi (800000 psi)

3ksi (3000 psi)

Rho

0.1 lb/in3

G1,Z

800ksi (800000 psi)

4ksi (4000 psi)

Yield

50ksi (50000 psi)

G2,Z

800ksi (800000 psi)

4ksi (4000 psi)

RHO

0.07 lb/in3

0.001074 lb/in3

Xt

35ksi (35000 psi)

500 psi

Xc

35ksi (35000 psi)

500 psi

Yt

35ksi (35000 psi)

500 psi

Yc

35ksi (35000 psi)

500 psi

S

4ksi (4000 psi)

150 psi

The optimization problem may be stated as Objective

Minimize mass.

Constraints

Composite skins must not fail. Aluminum ribs must not yield. Buckling must not occur.

Design Variables

Composite ply thicknesses. Rib thicknesses.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK.

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This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the tail_baseline.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The tail_baseline.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Model Creating Isotroic Materials and Properties; Assigning to Metallic Ribs Creating the Material 1. In the Model Browser, right-click and select Create > Material from the context menu. A default material displays in the Entity Editor. 2. For Name, enter al2024-t3. 3. Set Card Image to MAT1.

4. Enter the material values next to the corresponding fields. These values are taken from the table Aluminum 2024-T3 at the beginning of the tutorial. a) For E (Young's Modulus), enter 10.6e6. b) For NU, (Poisson's Ratio), enter 0.33. c) For RHO (Mass Density), enter 0.1

A new material, al2024-t3, has been created. The material uses OptiStruct's linear isotropic material model, MAT1.

Creating the Property 1. In the Model Browser, right-click and select Create > Property from the context menu. A default property displays in the Entity Editor. 2. For Name, enter Ribs.

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3. Set Card Image to PSHELL. 4. Enter the property values next to the corresponding fields. An empty Value field indicates that it is turned off. To edit these properties, click on the blank Value fields next to them and enter the required values. a) For Material, click Unspecified > Material. In the Select Material dialog, select a12024t3 and click OK. b) For T (thickness of the plate), enter 1.0. A new property, Ribs, has been created as a 2D PSHELL. Material information is also linked to this property.

Assigning Material and Property Data to the Ribs Component 1. In the Model Browser, right-click and select Create > Component from the context menu. A default component template displays in the Entity Editor. 2. For Name, enter Ribs.

3. For Property, click Unspecified > Property. In the Select Property dialog, select Ribs and click OK. A property collector named Ribs has been created. It has a PSHELL definition with a thickness of 1.0. It also references the Aluminum 2024-T3 material definition and the component name Ribs.

Figure 749:

Creating Materials and Geometric Properties using HyperLaminate Creating Orthotropic Material Properties 1. From the 2D page, click the HyperLaminate panel. HyperLaminate opens.

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2. Create the material definition, glass_fabric. a) In the Laminate Browser, right-click on MAT8 and select New from the context menu. A new material definition is created and appears in the Laminate Browser under MAT8. b) Under the Define, Edit material section, enter Glass_fabric in the Material field. c) Edit the following fields: E1

4Msi (4.0e6 psi)

E2

6Msi (6.0e6 psi)

NU12

0.1

G12

800ksi (800000 psi)

G1Z

800ksi (800000 psi)

G2Z

800ksi (800000 psi)

RHO

0.07 lb/in3

Xt

35ksi (35000 psi)

Xc

35ksi (35000 psi)

Yt

35ksi (35000 psi)

Yc

35ksi (35000 psi)

S

4ksi (4000 psi)

d) Click Apply. An orthotropic material definition for Glass_fabric is complete. 3. Create the material definition, core. a) In the Laminate Browser, right-click on MAT8 and select New from the context menu. A new material definition is created and appears in the Laminate browser under MAT8. b) Under the Define, Edit material section, enter Core in the Material field. c) Edit the following fields: E1

2ksi (2000 psi)

E2

4ksi (4000 psi)

NU12

0.3

G12

3ksi (3000 psi)

G1Z

4ksi (4000 psi)

G2Z

4ksi (4000 psi)

RHO

0.001074 lb/in3

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Xt

500 psi

Xc

500 psi

Yt

500 psi

Yc

500 psi

S

150 psi

d) Click Apply. Two new orthotropic material definitions have been created on the MAT8 branch of the Laminate Browser.

Creating Composite Laminates 1. In the Laminate Browser, right-click on PCOMP and select New from the context menu. A new laminate definition is created and appears in the Laminate Browser under PCOMP. 2. Under the Laminate definition section, edit laminate information. a) In the Name field, enter Inboard_section_top.

b) Click the color box and select a new color for the laminate. 3. Under Stacking sequence convention, set Convection to Symmetric-Midlayer. 4. Under Add/Update plies, edit ply information. a) Set Material to Glass_fabric. b) For Thickness T1, enter 0.25.

c) For Orientation (Degrees), enter 0.0. d) For No. of Repetitions, enter 1.0.

5. Click Add New Ply three times.

6. Under Ply lay-up order, edit the first ply (row 1). a) Set Material to Core. b) For Thickness T1, enter 0.5.

c) For Orientation (Degrees), enter 45. d) Set SOUT to YES.

7. Under Ply lay-up order, edit the second ply (row 2). a) For Orientation (Degrees), enter 90. b) Set SOUT to YES.

8. Under Ply lay-up order, edit the third ply (row 3). a) Set SOUT to YES.

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Figure 750:

9. Click Update Laminate. The Inboard_section_top laminate definition is complete.

Figure 751: Inboard_section Laminate

10. In the Laminate Browser, right-click Inboard_section_top and select Duplicate from the context menu. 11. Under the Laminate definition section, edit laminate information. a) In the Name field, enter Inboard_section_btm.

b) Click the color box and select a new color for the laminate. 12. Click Update Laminate. 13. Update the ply angles on the laminates Outboard_section_btm, Outboard_section_top, Midspan_section_btm, and Midspan_section_top to be the same as Inboard_section_top, then click Update Laminate. 14. From the menu bar, click File > Exit. HyperLaminate closes, and the laminate information is exported back to HyperMesh. Six laminate definitions have been created using the PCOMP keyword.

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Figure 752: Laminate Definitions

Assigning Newly Created Properties to the Associated Component At this point, the model is meshed and the material and geometric properties are defined. However, the elements are not referencing the correct property and material information. 1. Edit the component, Inboard_section_top. a) In the Model Browser, Component folder, select Inboard_section_top. The Entity Editor opens and displays the component's corresponding data. b) For Property, click Unspecified > Property. In the Select Property dialog, select Inboard_section_top and click OK. 2. Edit the component, Inboard_section_btm. a) In the Model Browser, Component folder, select Inboard_section_btm. The Entity Editor opens and displays the component's corresponding data. b) For Property, click Unspecified > Property. In the Select Property dialog, select Inboard_section_btm and click OK.

Arranging Elements in Respective Component Collectors 1. In the Model Browser, right-click on the Load Collector folder and select Hide from the context menu. 2. Edit the feature angle.

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a) Press O on the keyboard to open the Options panel. b) Select the mesh subpanel. c) In the feature angle= field, enter 37. d) Click return.

This allows you to select elements by feature angle. 3. From Tool page, click the organize panel. 4. Organize elements on the top inboard section into the Inboard_section_top component. a) Select one of the elements on the top inboard section. b) Click elems > by face. Several elements are selected on the top surface, stopping where the angle between elements is greater than 37 degrees. The ribs elements in between the top and bottom surface create a 90 degrees, thus the selection set stops here. c) Click dest component = and select Inboard_section_top. d) Click Move. 5. Organize the remaining elements into the correct component collectors indicated in Figure 753.

Figure 753:

6. In the Model Browser, Components folder, right-click on Tail and select Isolate Only from the context menu. Only the elements forming the ribs which are in the tail collector display. 7. Organize the elements forming the ribs in the Ribs component collector. a) In the Organize panel, click elems > displayed.

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b) Click dest component = and select Ribs. c) Click Move. d) Click return to exit the panel. 8. In the Model Browser, right-click on the Components folder and select Show from the context menu. 9. Clear empty components. a) Press F2 on the keyboard. b) Set the entity selector to comps. c) Click preview empty and delete entity to clear any empty components (the tail component in this case). d) Click return to exit the panel.

Orienting Elements 1. From Tool page, click the normals panel. 2. Select the elements subpanel. 3. Set the entity selector to elems, then click elems > by collector. 4. Select Ribs. 5. Click comps > reverse. 6. Click select. 7. Click display. Verify the element normals are not all in the same direction. 8. If element normals are not all in the same direction, adjust element normals. a) Under orientation, set the selector to elem and select an element whose normal is pointing inward. b) Click adjust. All skin normals should now point inwards. These skin normals are the local z-axes for each element. 9. Click return to return to the main menu. 10. From the 2D page, click the composites panel. 11. Select the material orientation subpanel. 12. Use the comps selector to select the components that contain all of the elements belonging to the skin. Note: This is all components, except Ribs. 13. Set Material orientation method to by vector. 14. Under by vector, select z-axis. 15. Click project. 16. Click return to exit the panel.

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The local x-axis of each of the selected elements is oriented to be the projection of the global z-axis. This is indicated by the small white arrows that appear on each element. Having defined the local x and z axes of the elements belonging to the component collectors Inboard_section_top, Inboard_section_btm, Midspan_section_top, Midspan_section_btm, Outboard_section_top, and Outboard_section_btm, you have fully established the local orientation for each element referencing a composite laminate.

Creating Static and Buckling Subcases Three loading scenarios are to be considered in this exercise: one where the tail experiences pressure loads on the bottom skin, a second where the tail experiences a tip load, and a third where the tail experiences both the pressure load and tip load simultaneously. In previous steps, a load collector containing the pressure loads and another containing the tip load were created, but a load collector containing both together is still needed. Next is to create a load collector which is a combination of the load collectors pressure and tip_load.

Creating Combination Load Collector 1. In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. 2. In the Name field, enter Combined. 3. Click Color and select a color from the color palette. 4. Set the Card Image to LOADADD. 5. For S, enter 1.0.

6. For LOAD_Num_Set = and enter 2.

This indicates how many load-collectors to combine.

7. In the Data: S1, field, click

.

8. In the LOAD_Num_Set= dialog, edit load collector information. a) For S1(1), enter 1.0.

b) For L1(1), select pressure. c) For S1(2), enter 1.0.

d) For L1(2), select tip_load. e) Click Close. A combination load collector, combining 1.0 times the loads in the pressure load-collector with 1.0 times the loads in the tip_load collector, is created.

Creating Static and Associated Buckling Subcase 1. From the menu bar, click View > Browsers > HyperMesh > Utility. 2. In the Utility tab, select FEA.

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3. Under LoadSteps, click Buckling. The Create Buckling Subcases opens. 4. Create a linear static subcase named pressure_only, which combines the pressure loads in the load-collector pressure with the single-point constraints in the load collector constraints, and an associated buckling eigenvalue subcase named buck_pressure_only which calculates the first 10 buckling modes greater than 0.0 for the pressure_only static subcase. a) In the Name field, enter pressure_only.

This is the user-defined name for the static subcase. If you call the static subcase name, then the associated buckling subcase will be named buck_name.

b) After the Name field, select EIGRL. This indicates that eigenvalue analysis is to be used to calculate the buckling modes. Currently this is the only option available. c) In the V1 field, enter 0.0.

This indicates that the lower bound for the eigenvalue extraction is 0.0. This prevents negative buckling modes being calculated (negative buckling modes indicate that buckling will occur if the loading is reversed).

d) Leave the V2 field blank. This is the upper bound for the eigenvalue extraction. You will select a number of modes to calculate (instead of a range of eigenvalues) for this exercise. e) In the ND field, enter 10.

This requests that the 10 lowest buckling modes (which are greater than V1) be calculated.

f) Set LOAD to pressure. g) Set SPC to constraints. h) Click Create. 5. Create a static subcase named tip_load_only, which combines the point loads in the load-collector tip_load with the single point constraints in the load collector constraints, and an associated buckling subcase which calculates the first 10 modes greater than 0.0. 6. Create a static subcase named combo, which combines the loads in the load-collector combined (that is, both pressure and tip_load) with the single point constraints in the load collector constraints, and an associated buckling subcase which calculates the first 10 modes greater than 0.0. 7. Exit the Create Buckling Subcases dialog.

Requesting Stress, Strain and Failure Results for Composite Laminates Stress, strain, and failure results are not output by default for composite laminates, but need to be requested. 1. Edit the property, Outboard_section_top. a) In the Model Browser, Properties folder, click Outboard_section_top. The Entity Editor opens and displays the properties card image. b) Set FT to HILL.

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This activates failure theory calculation. c) For SB, enter 3,500.

This is the interlaminate shear strength of the laminate, which is the bonding material shear strength. 3.5ksi is an assumed value, as no material data was provided.

d) In the Data: MID field, click

.

e) In the Number_of_Plies= dialog, set SOUT for all plies to YES and click Close. This requests stress and strain results to be output for all plies. 2. Repeat step 1 for the other composite laminates. 3. Edit the GLOBAL_CASE_REQUEST control card. a) From the Analysis page, click the control cards panel. b) In the Card Image dialog, click GLOBAL_CASE_REQUEST. c) Verify CSTRAIN and CSTRESS is selected. d) Click return twice to exit the dialog. Stress, strain, and failure results will now be output for the composite laminates.

Submitting the Job 1. From the Analysis page, click the OptiStruct panel.

Figure 754: Accessing the OptiStruct Panel

2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter tail_baseline_complete for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to analysis. 7. Set the memory options toggle to memory default.

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8. Click OptiStruct to launch the OptiStruct job. If the job is successful, new results files should be in the directory where the tail_baseline_complete.fem was written. The tail_baseline_complete.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Viewing the Results Reviewing the Analysis Summary File After running the OptiStruct analysis, the tail_baseline_complete.out file is written to your working directory. This file contains a summary of the analysis run. Using a text editor, open the tail_baseline_complete.out file. The file contains: • A summary of the finite element model. • A summary of the optimization parameters. • Memory and disk space estimations. • Analysis results. The Volume, Mass, and Buckling Modes for the baseline model are given in the analysis results section. ANALYSIS RESULTS : -----------------ITERATION

0

(Scratch disk space usage for starting iteration = 30 MB) (Running in-core solution) Volume

=

Subcase 1 3 5

Compliance 5.455666E+02 2.486638E+01 7.735856E+02

Subcase 2 2 2 2 2 2 2 2 2 2 4 4 4

Mode

1 2 3 4 5 6 7 8 9 10 1 2 3

Buckling Eigenvalue 1.583435E+01 1.610702E+01 1.638024E+01 1.665444E+01 1.681097E+01 1.693918E+01 1.715172E+01 1.723870E+01 1.739906E+01 1.748200E+01 8.267695E+01 8.326373E+01 8.393269E+01

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7.71079E+04

Mass

=

2.49519E+03

OptiStruct Tutorials Size Optimization 4 4 4 4 4 4 4 6 6 6 6 6 6 6 6 6 6

4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

p.841 8.466939E+01 8.541136E+01 8.618942E+01 8.695226E+01 8.765920E+01 8.834313E+01 8.907416E+01 1.329775E+01 1.351079E+01 1.372538E+01 1.394187E+01 1.416444E+01 1.417737E+01 1.439755E+01 1.445274E+01 1.464175E+01 1.466889E+01

Reviewing Displacment Results 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and the results are loaded. 2. On the Animation toolbar, set the Animation type to 3. On the Results toolbar, click

(Linear).

to open the Contour panel.

4. Set the Result type to Displacement [v] and Mag. 5. Click Apply. The displacement contour displays for the 1st subcase [pressure only]. You could also view the same for other subcases.

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Figure 755: Displacement Contour for pressure_only subcase.

Reviewing Stress Results 1. On the Visualization toolbar, click

to open the Entity Attributes panel.

2. Select Auto apply mode. 3. For Display, click Off. This will cause any component selected, either in the display or from the list of components, to be hidden. 4. Hide all of the components except the ribs. 5. On the Results toolbar, click

to open the Contour panel.

6. Set the Result type to Element Stresses (2D & 3D) [t] and von Mises. 7. Click Apply. A contour plot of the von Mises stresses for the metallic ribs displays.

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Figure 756:

8. On the Visualization toolbar, click

to open the Entity Attributes panel.

9. Click Flip. The Ribs component is now hidden and the composite laminate components are displayed. 10. On the Results toolbar, click

to open the Contour panel.

11. Set the Result type to Composite Stresses (s) and Ply Failure. 12. Set Layers to 1. 13. Click Apply. A contour plot of the composite failure indices from the composite skins results is displayed for the first layer.

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Figure 757: Failure index for the first layer for the pressure only loadstep

After calculating the failure indices for individual plies, OptiStruct calculates the potential failure index for the composite shell element. This is based on the premise that failure of a single layer qualifies as failure of the composite. Thus, a failure index for composite elements is calculated as a maximum of all computed ply and bonding failure indices. Note: Only plies with requested stress output are taken into account here. 14. Set Layers to Max. The maximum index for the laminate displays.

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Figure 758: Max failure index found on all layers for pressure only loadstep

Repeat this process to have the maximum failure index for all loadsteps. MAX FAILURE INDEX = 3.73 e-3 (Combo Loadstep)

Setting Up the Optimization Next you will setup the optimization problem in HyperMesh. The first step in this process is to define the design variables. The design variables for this exercise are the rib thicknesses and the laminates used in the composite skins.

Returning to HyperMesh Desktop HyperMesh Desktop allows you to use one HyperMesh page and multiple pages from the HyperView, HyperGraph, MotionView, and MediaView clients without having to switch applications.

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Return to HyperMesh Desktop by deleting the HyperView page or navigating back to the HyperMesh client. • To delete the HyperView page and return to the HyperMesh client, click

on the Page Controls

toolbar. • To keep the page open but return to the HyperMesh client page, click

/

in the top, right of the

application until the HyperMesh client returns.

Creating and Referencing a Thickness Design Variable for Metallic Ribs 1. From Analysis page, click the optimization panel. 2. Click the gauge panel. 3. Select the create subpanel. 4. Using the props selector, select the Ribs collector. 5. Set the top toggle to value from property. This sets the initial value of the design variable to be the thickness value defined on the property card. 6. Toggle lower bound % to lower bound =, then enter 0.01. This sets the lower bound for the design variable.

7. Toggle upper bound % to upper bound =, then enter 2.0. This sets the upper bound for the design variable.

8. Set type to PSHELL - T. 9. Click create. 10. Click return twice to go to the main page.

Figure 759: Gauge Panel Settings for Rib Thickness Design Variable

Creating Composite Laminate Design Variables 1. From the 2D page, click the HyperLaminate panel. HyperLaminate opens. 2. In the Laminate Browser, right-click on DESVAR and select New from the context menu. A new design variable, named NewDv1, is created. 3. In the Defne/Edit material section, edit the design variable.

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a) In the Material field, enter istgf_th.

istgf_th stands for (inboard_section_top, glass_fabric, and thickness).

b) In the Initial value field, enter 0.25.

c) In the Lower bound field, enter 0.01. d) In the Upper bound field, enter 1.0.

4. Click Apply.

5. Create one more design variables named isbgf_th using the same bounds as the istgf_th design variable. Tip: Quickly create an identical design variable by right-clicking on istgf_th in the Laminate Browser and selecting Duplicate from the context menu. 6. Review the other ten design variables in HyperLaminate and verify their bounds match the information in Table 4. Table 4:

Name

Initial Value

Lower bound

Upper bound

mstgf_th

0.25

0.01

1.0

msbgf_th

0.25

0.01

1.0

ostgf_th

0.25

0.01

1.0

osbgf_th

0.25

0.01

1.0

istc_th

0.5

0.01

2.0

isbc_th

0.5

0.01

2.0

mstc_th

0.5

0.01

2.0

msbc_th

0.5

0.01

2.0

ostc_th

0.5

0.01

2.0

osbc_th

0.5

0.01

2.0

Twelve total composite design variables now exist, one for the thickness of the glass fabric for each composite laminate component, and the other for the thickness of the core for each composite laminate component. As the laminates are symmetric, the glass fabric will reference the same design variables on either side of the core.

Updating Composite Laminate Properties

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1. In the Laminate Browser, under PCOMP, select Inboard_section_top. 2. Select Optimization. New fields appear in the Ply lay-up order table, allowing design variables to be associated to ply thicknesses or ply orientations. 3. In the first row of the Ply lay-up order table, set Thickness Designvar to istgf_th. Now the design variable istgf_th is associated to the thickness of the Glass_fabric material used in ply1, and, in this case, ply5 (as this is a symmetric-midlayer type laminate) of the Inboard_section_top component collector. 4. In the second row, set Thickness Designvar to istc_th. Now the design variable istc_th is associated to the thickness of the Core material used in ply2 and ply4 of the Inboard_section_top component collector. 5. In the third row, set Thickness Designvar to istgf_th. 6. Click Update Laminate to save the design variable assignments. 7. Repeat the above steps for the Inboard_section_btm composite laminate component collector, associating the appropriate design variables. 8. From the menu bar, click File > Exit. HyperLaminate closes, and the design variable and updated laminate information is exported back to HyperMesh.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the mass response, which is defined for the total volume of the model. a) In the responses= field, enter mass. b) Below response type, select mass.

c) Set regional selection to total and no regionid. d) Click create. 4. Create the composite failure response. a) In the response= field, enter hl_ist.

b) Set response type: to composite failure. c) Using the props selector, select the Inboard_section_top collector. d) Set the switch next to the props selector to hill. e) Click create. 5. Create the responses hl_osb, hl_ost, hl_msb, hl_mst, and hl_isb by repeating step 4 to create optimization responses for the hill failure criteria for the plies of the other composite laminate skins. 6. Create a static stress response. a) In the response= field, enter vm_strs.

b) Set the response type to static stress. c) Using the props selector, select Ribs.

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d) Set the response selector to von mises. e) Under von mises, select both surfaces. f) Click create. 7. Create the buckling response. a) In the response= field, enter buckle. b) Set response type: to buckling.

c) In the Mode Number field, enter 1.

d) Click create. The optimization response buckle, which is the lowest calculated buckling mode for the structure, is created. 8. Click return to go back to the Optimization panel.

Creating Constraints In this step you will define constraints. You will attempt to minimize the total mass of the structure, while keeping the von Mises stress in the metallic ribs below yield, the composite failure index of the composite skins below 1.0, and the buckling modes of the structure above 1.0. 1. Click the dconstraints panel. 2. Create the constraint, cnst1. a) In the constraints= field, enter cnst1.

b) Click response= and select vm_strs. c) Check the box next to upper bound, then enter 50,000.

d) Using the loadsteps selector, select pressure_only, tip_load_only, and combo. e) Click create. A constraint is defined on the von Mises stress of the metallic ribs to be less than 50ksi for all of the static subcases. 3. Create the constraint, cnst2. a) In the constraints= field, enter cnst2. b) Click response= and select hl_ist.

c) Check the box next to upper bound, then enter 1.0.

d) Using the loadsteps selector, select pressure_only, tip_load_only, and combo. e) Click create. A constraint is defined on the hill failure criteria for the Inboard_section_toplaminate to be less than 1.0. for all of the static subcases. 4. Create the cnst3 through cnst7 constraints by repeating step 3. 5. Create the constraint, cnst8. a) In the constraints= field, enter cnst8. b) Click response= and select buckle.

c) Uncheck the box next to upper bound.

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d) Check the box next to lower bound, then enter 1.0.

e) Using the loadsteps selector, select buck_pressure_only, buck_tip_load_only, and buck_combo. f) Click create. A constraint is defined on the lowest calculated buckling mode of the structure to be greater than 1.0 for all of the linear buckling subcases. 6. Click return to return to the optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

Creating Additional Run Parameters For the buckling constraint to be effectively maintained, an additional parameter needs to be defined. 1. Click the opti control panel. 2. Select MAXBUCK=. By default, the box preceding GBUCK= is checked automatically. 3. Click return. Together, these two options ensure that up to 10 modes are considered in the buckling constraint.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter tail_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job:

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OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file tail_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file. 9. Click Close.

Viewing the Results Reviewing the Optimization Summary File Using a text editor, navigate to the directory where you ran the OptiStruct optimization and open the tail_opt.out file. The tail_opt.out file contains: • A summary of the finite element model. • A summary of the optimization parameters. • Memory and disk space estimations. • An optimization iteration history. The value of the objective, the retained constraints, and the design variables are provided for all iterations in the optimization iteration history section. The final iteration provides information on the mass of the optimized structure, the values of the design variables for the optimized structure and the values of the objective and retained constraints for the optimized structure.

Reviewing the Iteration History 1. From the Page Controls toolbar, click

to create a new page with the HyperView client.

2. From the menu bar, click File > Open > Session. The Open Session File window appears. 3. In the Open Session File dialog, navigate to the directory where you ran the OptiStruct optimization and open the tail_opt_hist.mvw file. This is a HyperView session which creates plots of the objective, constraints, and design variables against iteration number using information from the tail_opt.hist file. The Figure 760 shows page 1 of the session, which is the plot of the objective against iteration. It shows how the mass decreased through the optimization process and how convergence is achieved when the change in mass levels out.

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Similar plots are available for the design variables and the constraints. There is also a plot showing the maximum constraint violation for a given iteration against iteration. When this value is zero, it indicates that there is no constraint violation.

Figure 760:

Comparing Baseline Results with Optimized Results 1. From the menu bar, click File > New > Session. A new session starts. 2. From the client selector, select

to change the current client to HyperView.

3. Click Yes to continue. 4. From the Page Controls toolbar, change the page layout to

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Figure 761:

5. Click the first window to activate it. The blue halo that surrounds the window indicates that it is active. 6. From the Standard toolbar, click

to load a new model file.

7. In the Load Model File dialog, navigate to the directory where you ran the OptiStruct baseline analysis and open the Tail_baseline_complete.h3d file. The path and file name for Tail_baseline_complete.h3d appears in the fields to the right of Load model and Load results. This is good because the Hyper3D format contains both model and results data. 8. Click Apply. The model and results are loaded in the current HyperViewwindow. 9. Click the second window to active it. 10. From the Standard toolbar, click

to load a new model file.

11. In the Load Model File dialog, navigate to the directory where you ran the OptiStruct optimization and open the tail_opt_s1.h3d file. For the optimization, analysis results are written to files named *_s#.h3d (static analysis results, where # is the subcase ID) and *_m#.h3d (eigenvalue analysis results, where # is the subcase number), while the density, thickness and shape results are written to the file *_des.h3d. 12. Activate the first window.

13. On the Results toolbar, click

to open the Contour panel.

14. Set the Result type to Displacement (v). 15. Click Apply. 16. Activate the second window. 17. In the Results Browser, select subcase 1 (pressure only) load case and the last iteration.

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Figure 762:

18. On the Results toolbar, click

to open the Contour panel.

19. Set the Result type to Displacement (v). 20. Click Apply. A side-by-side comparison of the displacement results before the optimization with those after the optimization displays. Notice the big change in the value of the total displacement. The optimized displacement results are greater than the baseline because you were optimizing for mass without displacement constraints.

Figure 763:

21. On the Animation toolbar, set the animation mode to 22. Click

(Linear static).

to animate the deformation. Click again to stop the animation.

Similar steps can be followed to compare stress and composite failure plots before and after the optimization.

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Notice how the maximum value for the composite failure index is almost at the design limit of 1.0.

Assign Thicknesses and Orientations In this step you will import the optimum property file to assign thicknesses and orientations. 1. From the menu bar, click File > New > Session. 2. From the client selector, select

to switch to the HyperMesh client.

All result information is cleared out of the client, including all pages. This will not affect your files on your hard drive. 3. From the menu bar, click File > Import > Solver Deck. 4. In the Import browser, click the optimization.

and open the tail_opt.fem file from the directory where you ran

5. Click Import. The *.fem that the optimization was run with is loaded into HyperMesh. 6. In the Import browser, click ran the optimization.

and open the tail_opt.prop file from the directory where you

The tail_opt.prop file is created by OptiStruct at the end of the optimization run and contains the optimized property data for model. 7. Expand the import options and select FE overwrite. 8. Click Import. 9. From the 2D page, click the HyperLaminate panel. 10. In HyperLaminate, review the new thicknesses assigned to the PCOMP properties.

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OS-T: 4070 Free-sizing Nonlinear Gap Optimization on an Airplane Wing Rib In this tutorial you will use an existing finite element model of an aluminum wing rib model to demonstrate how to do free-sizing optimization. HyperView is used to post-process the thickness pattern in the rib.

Figure 764: Wing Rib Model

There are four shell components in the model: the mounting flange, the web, the top and bottom flanges, and the lug. The web is connected to the lug by gap elements. Appropriate properties, loads, boundary conditions, and nonlinear subcases have already been defined in the model. The design region is the web and the rest of the components are non-design. Since a large portion of aerospace components are shell structures which are manufactured by machining or milling operations, freesizing optimization is very suitable for those components. To understand the limitations of topology optimization for such applications, a nonlinear gap topology optimization will also be done on the wing rib model. The optimization problem for this tutorial is stated as: Objective

Minimize weighted compliance WCOMP.

Constraints

Volume fraction on the web < 0.3.

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Design Variables for Free Sizing Optimization

Thickness of each shell element in the design space.

Design Variables for Topology Optimization

Element density of each element in the design domain.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Performing a Free-Sizing Nonlinear Gap Optimization Opening the Model 1. Click File > Open > Model. 2. Select the rib_complete.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The rib_complete.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Free-sizing Optimization Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the free size panel. 3. Select the create subpanel. 4. In the desvar= field, enter shells. 5. Set type to PSHELL.

6. Using the props selector, select the Web component. 7. Click create.

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Creating Free-sizing Manufacturing Constraints 1. Select the parameters subpanel. 2. Click desvars and select shells. 3. Toggle minmemb off to mindim =, and enter 2.0. 4. Click update. 5. Click return.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume fraction response. a) In the responses= field, enter Volfrac.

b) Below response type, select volumefrac. c) Set regional selection to total and no regionid. d) Click create. 4. Create the weighted component response. a) In the responses= field, enter wcomp.

b) Below response type, select weighted comp. c) Click loadsteps, then select all loadsteps. d) Click return. e) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter vol.

3. Click response = and select volfrac. 4. Check the box next to upper bound, then enter 0.3. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response= and select wcomp.

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4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rib_freesize for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file rib_freesize.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

The default files that get written to your run directory include: rib_freesize.hgdata HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration. rib_freesize.hist The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history. rib_freesize.HM.comp.tcl HyperMesh command file used to organize elements into components based on their density result values. This file is only used with OptiStruct topology optimization runs. rib_freesize.HM.ent.tcl HyperMesh command file used to organize elements into entity sets based on their density result values. This file is only used with OptiStruct topology optimization runs. rib_freesize.html HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration. rib_freesize.mvw HyperView session file.

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rib_freesize.oss OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results. rib_freesize.out OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the rib_freesize.fem file. rib_freesize.res HyperMesh binary results file. rib_freesize.sh Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run. rib_freesize.stat Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on. rib_freesize_des.h3d HyperView binary results file that contain optimization results. rib_freesize_frame.html HTML file used to post-process the .h3d with HyperView Player using a browser. It is linked with the _menu.html file. rib_freesize_hist.mvw Contains the iteration history of the objective, constraints, and the design variables. It can be used to plot curves in HyperGraph, HyperView, and MotionView. rib_freesize_menu.html HTML file used to post-process the .h3d with HyperView Player using a browser. rib_freesize_s#.h3d HyperView binary results file that contains from linear static analysis, and so on. rib_freesize.fsthick The element definitions for those elements that were part of a free size design space. The optimized thickness of these elements is provided as nodal thickness values (Ti).

Viewing the Results Element thickness distributions are output from OptiStruct for all iterations. In addition, Displacement and Stress results are output for each subcase for the first and last iteration by default. This section describes how to view those results in HyperView. 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and the results from the rib_freesize.h3d file are loaded. 2. On the Visualization toolbar, click

to open the Entity Attributes panel..

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3. Select Auto appy mode: Display Off, then select the Web component. All of the components are undisplayed except Web. 4. Click the Mesh shaded mesh option

.

5. Click the Web component to get a shaded mesh. 6. On the Results toolbar, click

to open the Contour panel.

7. Set the Result type to Element Thicknesses. 8. In the Results Browser, select the last iteration listed in the Simulation list.

Figure 765:

9. On the Standard Views toolbar, click

to show the top view of the Web.

The contour element thickness on the Web component displays. The result from free-sizing optimization is a web with optimized thickness distribution that can be reduced subsequently into larger zones for simplification of the manufacturing process. Moreover, the design obtained from free-sizing offers the freedom to create cavities, ribs, and varying thickness simultaneously, which is not possible in topology optimization.

Figure 766: Thickness contour from free-sizing nonlinear gap optimization on the Web of plate thickness 0.1mm

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OptiStruct Tutorials Size Optimization 10. On the Page Controls toolbar, click

p.862 to close the HyperView client pages until the HyperMesh

client displays.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter rib_complete.hm for the file name and save it to your working directory.

Performing a Topology Nonlinear Gap Optimization Setting Up a Topology Optimization with Nonlinear Gap Elements Creating Topology Design Variables 1. In the Model Browser, right-click on the Design Variable folder and select Delete from the context menu. 2. From the Analysis page, click the optimization panel. 3. Click the topology panel. 4. Select the create subpanel. 5. In the desvar = field, enter shells.

6. Using the props selector, select the Web component. 7. Set type to PSHELL. 8. Leave the base thickness as 0.0. 9. Click create. The web component has now been defined as the design component for topology optimization.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter rib_topology.hm for the file name and save it to your working directory.

Creating Topology Optimization Manufacturing Constraints 1. Select the parameters subpanel. 2. Click desvars = and select shells. 3. Toggle minmemb off to mindim =, then enter 2.0 for minimum member size control.

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4. Click update. 5. Click return twice.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rib_topology for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file rib_topology.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Element density results are output from OptiStruct for all iterations. In addition, displacement and stress results are output for each subcase for the first and last iteration by default. 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and the results from the rib_topology.mvw file are loaded. This file is linked with the .h3d file where the model and results are defined. 2. On the Visualization toolbar, click

to open the Entity Attributes panel..

3. Select Auto appy mode: Display Off, then select the Web component. All of the components are undisplayed except Web. 4. Click the Mesh shaded mesh option

.

5. Click the Web component to get a shaded mesh. 6. On the Results toolbar, click

to open the Contour panel.

7. Set the Result type to Element Densities. 8. In the Results Browser, select the last iteration listed in the Simulation list.

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p.864 to show the top view of the Web.

10. Click Apply to show the contour of element density on the Web component. The results from topology optimization show very discrete results as expected.

Figure 767: Contour of element density on the Web component from topology nonlinear gap optimization

Reviewing and Comparing Results from Free-size Optimization and Topology Optimization Results from the topology optimization show a truss type design with extensive cavities and voids, while the results from free-sizing optimization tend to come up with shear panels. While solid/void density distribution is the only choice for solid elements; for shell structures, intermediate densities can be interpreted as different thicknesses and penalizing then could result in potentially inefficient shell structures. Moreover, since a large portion of aerospace structures are shell structures, a shear panel type design is often desirable for manufacturing purposes especially for machine milled shell structures. Free-sizing optimization can prove to be very beneficial in those situations.

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OS-T: 4080 Minimization of the Maximum Stress of a Rotating Bar In this tutorial you will set up and run a multibody dynamics (MBD) size optimization of a rotating bar. Angular velocity at the revolute joint defined left end of the bar is 10*SIN(2*TIME) rad/sec. The objective is to minimize the maximum stress of the structure subject to certain mass specifications. The bar consists of five bar elements with a solid circle cross section (each element has its own PBARL with ROD cross section). The design variables are the radius of each bar property.

Figure 768: Structural Model of a Rotating Bar

The optimization problem is stated as: Objective

Minimize maximum normal stress.

Constraints

Mass < 10kg.

Design Variables

Radius of each bar properties (PBARL).

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the rotating_bar_design.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files.

3. Click Open. The rotating_bar_design.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

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Setting Up the Model Defining Boundary Conditions for Structural Analysis Structural analysis and optimization of the flexible bodies of this model are performed in ESL optimization. Thus, the boundary condition for the flexible bodies needs to be defined. 1. Create a load collector. a) In the Model Browser, right-click and select Create > Load Collector from the context menu. A default load collector displays in the Entity Editor. b) In the Name field, enter BCforOpt.

2. Enable coincident picking.

a) From the menu bar, click Preferences > Graphics. b) Select the graphics subpanel. c) Select coincident picking. d) Click return.

Figure 769:

3. In the Model Browser, click

to display the properties view.

4. Create constraints. Only 6 dof per flexible body should be fixed to remove 6 rigid body motion of each flexible body. a) From the Analysis page, click the constraints panel. b) Click the left end of the model. Two node numbers display. c) Select node number 1.

Figure 770:

d) Select all dofs (dof1 to dof6), and verify that their values are set to 0.0. e) Click create.

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f) Click return.

Defining a Driving Motion Not Supported by HyperMesh In this tutorial, the driving motion at a joint, MOTNJE is defined. However, MOTNJE is currently not supported by HyperMesh. Thus, you need to enter this card and a corresponding MBVAR card manually. 1. From the Analysis page, click the control cards panel. 2. Click BULK_UNSUPPORTED_CARDS. 3. Verify the following two cards are listed. If they are not listed, enter the cards.

Figure 771:

4. Click OK. 5. Click return.

Editing the Load Step 1. In the Model Browser, click SUBCASE1. The load step's data displays in the Entity Editor. 2. In the Name field, enter Dynamic.

3. Set the Analysis type to multi-body dynamics. 4. Define SPC. a) For SPC, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select BCforOpt and click OK. 5. Define MBSIM. a) For MBSIM, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select MBSIM1 and click OK.

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6. Define MOTION. a) For MOTION, click Unspecified > Loadcol. b) In the Select Loadcol dialog, select MBSIM1 and click OK.

Setting Up the Optimization Defining the Size Optimization Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the size panel. 3. Select the desvar subpanel. 4. Create the design variable, rad1. a) In the desvar = field, enter rad1.

b) In the initial value = field, enter 10.

c) In the lower bound = field, enter 0.05. d) In the upper bound = field, enter 100.

e) Set the move limit toggle to move limit default. f) Set the discrete design variable (ddval) toggle to no ddval. g) Click create. A design variable, rad1, has been created. The design variable has an initial value of 10, a lower bound of 0.05, and an upper bound of 100. 5. Create the design variable rad2, rad3, rad4, and rad5 using the same initial value, lower, and upper bounds as rad1. 6. Select the generic relationship subpanel. 7. Create a design variable property relationship, bar1_rad1. a) In the name = field, enter bar1_rad1.

b) Using the prop selector, select PBARL_1. c) Under the props selector, select Dimension 1. d) Click designvars. e) Select rad1. Notice: The linear factor is automatically set to 1.000. f) Click return. g) Click create. A design variable to property relationship, bar1_rad1, has been created relating the design variable rad1 to the radius entry on the PBARL card for property PBARL_1.

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8. Create the design variable to property relationship bar2_rad2, bar3_rad3, bar4_rad4, and bar5_rad5 relating the design variables to the radius entry on the PBARL cards for the property PBARL_2, PBARL_3, PBARL_4, and PBARL_5. 9. Click return to go to the optimization panel.

Creating the Mass and Stress Responses 1. Create the response, Mass. a) Click the responses panel. b) In the response = field, enter Mass. c) Set the response type to mass.

d) Set the regional selection to total (this is the default). e) Click create. A response, mass, is defined for the total mass of the model. 2. Create the response, Stress. a) Click the responses panel. b) In the response = field, enter Stress.

c) Set the response type to static stress. d) Click props. e) Select all of the properties in the list and click select. f) Set the stress to normal. g) Set the stress recovery point to all. h) Click create.

Figure 772:

3. Click return to go to the optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter Mass.

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3. Click response = and select Mass. 4. Check the box next to upper bound, then enter 10.0. 5. Click create.

6. Click return to go back to the Optimization panel.

Defining the Objective Function The objective of this tutorial is to minimize the maximum stress of the model while the model rotates. 1. Create an objective reference. a) Click the obj reference panel. b) In the dobjref= field, enter MaxStress. c) Click response= and select Stress.

d) Select neg reference= and pos reference=. e) Switch the toggle from all to loadsteps, then use the loadsteps selector to select Dynamic. f) Click create. g) Click return to go back to the Optimization panel. 2. Define the objective. a) Click the objective panel. b) Select minmax. c) Using the dobjrefs= selector, select MaxStress. d) Click create. e) Click return to go back to the Optimization panel.

Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter rotating_bar_design.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter rotating_bar_design for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog.

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5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. 9. Click Close. If the optimization was successful, no error messages are reported to the shell. The optimization is complete when the message Processing completed successfully appears in the shell. If the job was successful, the new results file can be seen in the directory where the input file was saved. In addition to ordinary output files, you can see a text file with the name rotating_bar_design.eslout. This file is a good source to see the process of the ESL optimization. After ~ 7 interations, the model should converge to the descending values shown in Figure 773.

Figure 773:

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OS-T: 4090 Manufacturing Constraints of a Composite Structure In this tutorial you will perform a free-size optimization with manufacturing constraints. One of the advantages with composite materials is that the structural performance can be controlled precisely by choosing the appropriate ply thickness, ply orientation, stacking sequence, ply materials, and so on. The ability to vary many different parameters provides greater flexibility, but at the same time it is tougher to optimize the part as the number of design variables increases many fold. OptiStruct has the ability to directly or indirectly optimize the ply thickness, ply orientation and stacking sequence for composite structures. Free-size optimization handles the thickness of each ply in each element as a design variable and optimizes the structure by determining the optimal thickness distribution for each ply in the laminate. For several reasons, every composite manufacturer has their own manufacturability standards for the laminated composites. These additional manufacturing constraints are to be included with freesize optimization to achieve an acceptable manufacturing solution. OptiStruct supports different manufacturability constraints that can be defined with free-size optimization. This tutorial helps explain the procedure used to define the manufacturing constraints in the free-size optimization of composite structures. The optimization problem for this tutorial is stated as: Objective

Minimize the Mass.

Constraints

Displacement of selected 6 nodes < 3 mm.

Design Variables

Thickness of each ply of each element in the design space.

Figure 774: Composite Wing Model

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Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the Composite_Wing.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Composite_Wing.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Reviewing the Model Setup The model is already set up for the analysis. The model properties, loads, boundary conditions, and loadsteps are already defined. The model has 15 components out of which the TopSkin and BottomSkin components are defined with the composite property PCOMP. The rest of the components are defined with PSHELL property which references the material property, Aluminum. In this step you will use HyperLaminate to define, review, and edit ply lay-up information. Size design variables can also be set up in this panel for performing size optimization.

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Figure 775: Wing geometry

1. From the 2D page, click the HyperLaminate panel. HyperLaminate opens. 2. In the Laminate Browser, Laminates section, click TopSkin. The TopSkin component properties display in the Laminate definition and Review sections. The Laminate definition section shows the ply material, ply thickness, ply orientation, and so on, which is shown graphically under the Review section. 3. From the menu bar, click File > Exit to exit HyperLaminate and return to HyperMesh.

Setting Up the Optimization Creating Design Variable In this step you will create the design variable for free-sizing optimization. 1. From the Analysis page, click the optimization panel. 2. Click the free size panel. 3. Select the create subpanel. 4. In the desvar= field, enter Skins. 5. Set type: to PCOMP(G).

6. Using the props selector, select the TopSkin and BottomSkin properties. 7. Clicks create.

Adding a Minimum Dimension Manufacturing Constraints You should still be in the free size panel.

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In this step you will define the minimum member size control to be 5.0. Member size control gives you some control over the member size in the final free-size design and the resulting structure will have discrete members that are easy to interpret during post-processing. 1. Select the parameters subpanel. 2. Click desvars= and select Skins. 3. Toggle minmemboff to mindim =, and enter 5.0. 4. Click update.

Adding Minimum Thickness Manufacturing Constraints You should still be in the free size panel. In this step you will define the percentage following manufacturing constraints. • Minimum laminate thickness of 0.2. • A Minimum of 10% and a maximum of 60% thickness (of total laminate thickness) constraints defined for all the plies. This means that for each element, none of the plies will have thickness less than 10% or greater than 60% of the totals laminate thickness. • The thickness of ply with ply angle of 45 degree to be same as the thickness of ply with ply angle of -45 degree. 1. Select the composites subpanel. 2. Click desvars= and select Skins. 3. Under laminate thickness, toggle minimum thickness off to minimum thickness = and enter 0.2. 4. Click update. The above defined minimum laminate thickness constraint is updated to the free-size design variable. 5. Click edit. 6. In the Card Image dialog, select PLYPCT. 7. Under PLYPCT, select BYSET. 8. In the DSIZE_NUMBER_OF_PLYPCT= field, enter 4.

This specifies that ply percentage constraints will be defined on 4 plies. In the Card Image dialog, four additional lines appear, in which you can enter the ply percentage constraints. PANGLE

Ply orientation to which the PLYPCT constraints are applied.

PPMIN

Minimum ply percentage thickness for the PLYPCT constraint.

PPMAX

Maximum ply percentage thickness for the PLYPCT constraint.

PTMAN

Manufacturable ply thickness.

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Figure 776:

9. In the first COMP PLYPCT row, edit the PANGLE, PPMIN, PPMAX, and PTMAN constraints. a) For PANGLE, enter 0.

This define that ply percentage constraints are defined for the ply with ply angle of 0 degree.

b) For PPMIN, enter 0.1.

c) For PPMAX, enter 0.6.

d) Leave the PTMAN field blank. This defines that for each element, the thickness of the ply with ply angle 0, should be no less than 10% or more than 60% of the total thickness. 10. In the second COMP PLYPCT row, edit the PANGLE, PPMIN, PPMAX, and PTMAN constraints. a) For PANGLE, enter 45. b) For PPMIN, enter 0.1.

c) For PPMAX, enter 0.6.

d) Leave the PTMAN field blank. 11. In the third COMP PLYPCT row, edit the PANGLE, PPMIN, PPMAX, and PTMAN constraints. a) For PANGLE, enter -45. b) For PPMIN, enter 0.1.

c) For PPMAX, enter 0.6.

d) Leave the PTMAN field blank. 12. In the second COMP PLYPCT row, edit the PANGLE, PPMIN, PPMAX, and PTMAN constraints. a) For PANGLE, enter 90. b) For PPMIN, enter 0.1.

c) For PPMAX, enter 0.6.

d) Leave the PTMAN field blank. 13. Select BALANCE. The BALANCE constraint ensures that two plies will always be of equal thickness. BALANCE

BALANCE flag indicating that a balancing constraint is applied.

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BANGLE1

First ply orientation to which the BALANCE constraint is applied.

BANGLE2

Second ply orientation to which the BALANCE constraint is applied.

14. In the BALANCE row, edit the BANGLE1 and BANGLE2 constraints. a) For BANGLE1, enter 45.

b) For BANGLE2, enter -45.

This defines that the plies with ply angle of 45 and -45 will always have the same thickness. 15. Click return to return from the panel. 16. Click update to update the above defined manufacturing constraints to the free-size design variable. 17. Click return to return from the free size panel.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the mass response, which is defined for the total volume of the model. a) In the responses= field, enter mass. b) Below response type, select mass.

c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter disp.

b) Below response type, select static displacement. c) Click nodes > by sets, then select Nodes and click select. 6 nodes at the end side of the wing are selected. d) Set the displacement type to dof3. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

e) Click create. 5. Click return to go back to the Optimization panel.

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Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter disp_constr. 3. Click response = and select disp.

4. Check the box next to upper bound, then enter 2.0.

5. Using the loadsteps selector, select Subcase1 and Subcase2. 6. Click create. 7. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Wing_FreeSize_with_PLYPCT for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file Wing_FreeSize_with_PLYPCT.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

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Viewing the Results OptiStruct provides element thickness, ply thickness information for all iterations, and also writes out displacement and von Mises stress results for the linear static analysis. This section describes how to view the results in HyperView.

Viewing a Contour Plot of Element and Ply Thicknesses 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads all .h3d result files. 2. On the Results toolbar, click

to open the Contour panel.

3. Set the Result type to Element thicknesses and Thickness. 4. Click Apply. The contour of total laminate thickness for the selected iteration displays. 5. In the Results Browser, select the last design iteration result.

Figure 777:

The contoured thickness is the optimal laminate thickness distribution for the current design.

Viewing a Contour Plot of Ply Thickenesses Since only the TopSkin and BottomSkin components are in the free-size design space and the thickness of only these two components are changing, it is convenient to view only these two components. Also, for easy visualization purposes, it is convenient to move the two surfaces apart as they are very close to each other. 1. On the Results toolbar, click

to open the Iso panel.

2. Click Apply. The isometric view of the model displays. 3. In the Results Browser, click

to activate the Component view.

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Figure 778:

4. From the view controls in the Results Browser, click

(Isolate Shown) and click the

BottomSkin and TopSkin components. The two components are isolated. 5. On the Visualization toolbar, click

to open the Exploded View panel.

6. Click Add to add a new explosion view. 7. Click one of the components to select it for translating. 8. Under Translate, set the Direction to X Axis. 9. In the Distance field, enter 5.

10. Click + to move the selected component in the positive X direction. Repeat until the component is moved enough to view both the components.

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Figure 779: Laminate Optimized Thickness Contour

11. On the Results toolbar, click

to open the Contour panel.

12. Set the Result type to Ply Thickness and Thickness. 13. Set Entity with Layer to 1. 14. Click Apply. The first ply thickness contour displays. You can repeat these steps to plot the thickness for Ply 2, Ply 3, and Ply 4 or Max, and so on.

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Figure 780: First Ply Optimized Thickness Contour

Verify if all the manufacturing constraints (ply percentage, balance and minimum laminate thickness) are satisfied. Additionally, open the Wing_FreeSize_with_PLYPCT.out file in a text editor and verify that the displacement constraints are satisfied in the last iteration.

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OS-T: 4095 Size Optimization using External Responses (DRESP3) In this tutorial, the standard responses available in OptiStruct are passed to a HyperMath script and the newly created responses from the script are used as optimization constraints. Since HyperMath is an interpreter, you can build custom responses without having to compile your HyperMath script. You will load the structural model into HyperMesh. The materials, shell properties, loads and boundary conditions are already defined in this model. The thicknesses of the three components are identified as design variables. The von Mises stress of element numbers 58 and 59 (elements located on the circumference of the hole) are defined as responses, and a total volume response is defined as well. The von Mises stress of elements 58 and 59 are passed as inputs to the HyperMath script which in turn, returns two values: the sum of the two von Mises stresses, and the average value of the two elemental von Mises stresses. The optimization problem for this tutorial is stated as: Objective

Minimize volume.

Constraints

Constraints on the sum of the von Mises stresses and the average von Mises stress.

Design Variables

Gauges of the three parts.

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Figure 781:

Launching HyperMath 1. Launch HyperMath. 2. From the menu bar, click File > Open. 3. In the Open File dialog, open the dresp3_simple_h.hml file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 4. Examine the HyperMath script to calculate external responses.

The HyperMath script identified with the function MYSUM takes two inputs, rparam[1] and rparam[2], and returns two responses, rresp[1] - sum of the two inputs, and rresp[2] average value of the two inputs. The calculated responses rresp[1] and rresp[2] are sent back to OptiStruct for use in the optimization. The script above will be linked to the DRESP3 related cards in the OptiStruct input file, which will pass the two inputs to this script and then receive two outputs from this script.

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Note: In this script, it is possible to assign any name to the function, like MYSUM, myresponses, sumandavg, etc. However, the argument names to the function such as iparam, rresp, rparam, and so on. cannot be changed. External responses will now be set up using DRESP3.

Figure 782:

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK.

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This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Importing the Model 1. Click File > Import > Solver Deck. An Import tab is added to your tab menu. 2. For the File type, select OptiStruct. 3.

Select the Files icon . A Select OptiStruct file browser opens.

4. Select the dresp3_simple.fem file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 5. Click Open. 6. Click Import, then click Close to close the Import tab.

Setting Up the Optimization Attaching the HyperMath Script Library to OptiStruct OptiStruct will need the location of the HyperMath script for it to pass and receive the necessary inputs and outputs respectively. This is achieved using the LOADLIB card. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click LOADLIB. 3. Enter inputs. a) Set Type to DRESP3. b) In the GROUP field, enter HLIB.

c) In the PATH field, enter the location of the .hml file. Example: c:/temp/dresp3_simple_h.hml Note: There is a limited amount of space within the HyperMesh Desktop to enter the file path and name. If the full file path with file name does not fit, exit the panel and edit the rest manually. 4. Click return.

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Creating Design Variables In this step you should still be in the Card Image dialog. The design variables for the thicknesses of the three components are already defined. The responses for the total volume and the von Mises stress of elements 58 and 59 have also been defined. The DRESP3 bulk data entry is not supported in the current version of HyperMesh. Therefore, these cards will be defined in the BULK_UNSUPPORTED_CARDS panel. Note: A '$' symbol indicates a comment and the following data will not be read by the solver. 1. Click BULK_UNSUPPORTED_CARDS. 2. In the Control Card dialog, enter in the following DRESP3 information:

Figure 783:

This defines two external responses: the sum of the von Mises stresses of elements 58 and 59 (SUMH) and the average von Mises stress for elements 58 and 59 (AVGH). The DRESP3 responses have different IDs from the DRESP1 responses and point to the library called HLIB defined. Also, the function MYSUM is the same function name in the dresp3_simple_h.hml script. This completes linking of the DRESP3 cards with the HyperMath Script.

Creating Constraints In this step you should still be in the Control Card dialog.

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Since the DRESP3 card is not supported in the current version of HyperMesh, the DCONSTR cards cannot be assigned to the DRESP3 responses from the dconstraints panel either. The DCONSTR cards are therefore also added using the BULK_UNSUPPORTED_CARDS panel. 1. In the Control Card dialog, enter the following constraint data (DCONSTR and DCONADD) following the DRESP3 information:

Figure 784:

2. Click OK. 3. Click return. The upper bound constraints of 50 and 25 on the SUMH response and the AVGH response are now defined.

Running the Optimization 1. Export the dresp3_simple.fem file.

a) From the menu bar, click File > Export > Solver Deck. b) Select the export directory for the solver file. c)

In the Export browser, click

d) Click Export.

, select the file dresp3_simple.fem, and click Save.

The .fem file name is used for OptiStruct input decks.

2. Edit the dresp3_simple.fem file.

a) In a text editor, open the dresp3_simple.fem file.

b) Under the subcase information section, add DESSUB = 10.

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c) Save the file. The DRESP3s created are subcase dependent responses and therefore are to be referenced from within a subcase. The DESSUB command does this. This line has to be added manually since the current version of HyperMesh does not support the DRESP3 Bulk Data Entry.

3. Run the optimization.

a) From the Start menu, click All Programs > HyperWorks 2019 > OptiStruct. b) In OptiStruct, open the dresp3_simple.fem file. c) Click Run.

4. When the job is complete, post-process the results. Note: The complete FEM deck, dresp3_simple_complete.fem, is available and can be used as a reference.

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Shape Optimization

13

Shape Optimization

This chapter covers the following: •

OS-T: 5000 2D Shape Optimization of a Cantilever Beam (p. 891)

•

OS-T: 5010 Cantilever L-beam Shape Optimization (p. 902)

•

OS-T: 5020 3D Bracket Model using the Free-shape Method (p. 910)

•

OS-T: 5030 Buckling Optimization of a Structural Rail (p. 923)

•

OS-T: 5040 Rail Joint (p. 933)

•

OS-T: 5050 4 Bar Linkage (p. 953)

•

OS-T: 5060 3D Model using the Free-shape Method with Manufacturing Constraints (p. 964)

•

OS-T: 5070 Fatigue Optimization of a Torque Control Arm (p. 972)

•

OS-T: 5080 Global Search Optimization (p. 983)

•

OS-T: 5090 Thermal Optimization on Aluminum Fins (p. 989)

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OS-T: 5000 2D Shape Optimization of a Cantilever Beam In this tutorial you will perform a shape optimization on a cantilever beam modeled with shell elements. You will use a structural model with loads and constraints. The deflection at the lower right corner should be limited to 3mm. The optimal design would use as little material as possible.

Figure 785: Cantilever Beam, Structural Model

The structural model is loaded into HyperMesh and is used to generate and run a shape optimization of the cantilever beam. Shape perturbation vectors are generated using HyperMorph, which is accessed, through the HyperMesh interface. The OptiStruct software determines the optimal shape. The results are then reviewed in HyperView. The optimization problem for this tutorial is stated as: Objective

Minimize volume.

Constraints

Given maximum nodal displacement at the end of the beam < 3.0 mm.

Design Variables

Shape variables defined with HyperMorph.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK.

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This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model. 2. Select the beamshape.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The beamshape.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Shapes using HyperMorph In this step you will use HyperMorph to create shapes. 1. From the Analysis page, click the optimization panel. 2. Click the HyperMorph panel. 3. Create domain handles. a) Click the domains panel. b) Select the create subpanel. c) Switch from global domains to auto functions and keep the default settings. d) Click generate. e) Click return to return to the HyperMorph panel. A number of domains and handles are created which will enable us to morph the shape of the beam. There are two types of handles: global handles, which are represented by larger red balls; and local handles, which are represented by smaller yellow balls. Only local handles will be covered in this tutorial. 4. Move handles. a) Select the morph panel. b) Select the move handles subpanel. c) Switch interactive to move to node. d) Using the handles selector, select the top right local handle (where the force is applied).

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Figure 786:

e) Using the nodes selector, select the node in the middle of the right-hand side of the beam. The beam changes shape, so that the handle you selected moved to the location of the node you selected. Notice how the mesh adjusted to this change in shape.

Figure 787: Morphed Shape 1

5. Save the shape. a) Select the save shape subpanel. b) In the shape= field, enter shape1.

c) Click the color button to select a new color for the shape vectors. d) Under shape=, set the toggle to as node perturbations. e) Click save. f) Click Yes. This shape has been saved, and can be associated with a design variable later. 6. Click undo all. The model returns to the original shape. 7. Click return to return to the HyperMorph panel. 8. Create handles. a) Select the handles panel. b) Select the create subpanel. c) In the name = field, enter aux1.

d) Using the domain selector, select the top edge domain. Tip: To ensure that you select the top edge domain, hold down the left mouse button and move the mouse over the top edge of the beam until the edge is highlighted (white), then release the mouse button. e) Set the toggle to by nodes.

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f) Using the nodes selector, select the node at the center of the top edge of the beam. g) Click create. h) Click return to return to the HyperMorph panel. A new handle, 'aux1', is created at the center of the top edge of the beam.

Figure 788:

9. Move the handles. a) Click the morph panel. b) Select the move handles subpanel. c) Switch from move to nodes to interactive. d) Using the handles selector, select the yellow handle you just created. A manipulator axis is created on the selected handle. e) Left-click and hold down the mouse button on the manipulator axis pointing in the positive X direction. While holding the mouse button down, pull the selected axis in the positive X direction. Pull down approximately until the center of the beam and release the mouse button. Notice: The mesh morphs interactively as the handle moves along the axis.

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Figure 789: Morphed Shape 2

10. Set biasing. a) Select the set biasing subpanel. b) Using the handles selector, select aux1. c) Select make retroactive. d) Switch bias to screen edit. The number 1.000 appears next to the handle 'aux1'. e) Click the number and hold the mouse button down until the value reads 1.500. Tip: If you move the mouse upwards the number increases, if you move the mouse downwards the number decreases. f) Click update. The curvature of the top edge has altered.

Figure 790: Morphed Shape 3

11. Save the shape.

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a) Select the save shape subpanel. b) In the shape= field, enter shape2.

c) Click the color button to select a new color for the shape vectors. d) Under shape=, set the toggle to as node perturbations. e) Click save. f) Click Yes if you wan to save perturbations for nodes at global and morph volume handles. This shape is now saved, later it can be associate to a design variable. 12. Click undo all. The model returns to its original shape. 13. Click return twice to return to the OptiStruct panel.

Creating Shape Design Variables 1. Click the shape panel. 2. Select the desvar subpanel. 3. Switch the design variable option from single desvar to multiple desvars. 4. Using the shapes selector, select shape1 and shape2. 5. Click create. 6. Click return to return to the Optimization panel. Two shape design variables are created using the shapes that were saved earlier.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the volume response, which defines the volume fraction of the design space. a) In the responses= field, enter vol.

b) Below response type, select volume. c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter disp.

b) Below response type, select static displacement. c) Click nodes > by id, then enter 1115 in the id= field. d) Set the displacement type to dof1. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

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total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

e) Click create. 5. Click return to go back to the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter constr. 3. Click response = and select disp.

4. Check the box next to upper bound, then enter 3.0. 5. Using the loadsteps selector, select Load. 6. Click create. 7. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select vol. 4. Click create. 5. Click return twice to exit the Optimization panel.

Defining the SHAPE Card Only displacement and stress results are available in the _s#.h3d file by default. In order to look at displacement/stress results on top of a shape change that was applied to the model in HyperView, a SHAPE card needs to be defined. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click SHAPE. 3. Set FORMAT to H3D. 4. Set TYPE to ALL. 5. Set OPTION to ALL. 6. Click return twice to go back to the main menu.

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Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter beamshape for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file beamshape.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Viewing the Shape Results 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads beamshape_des.h3d on page 1 and beamshape_s2.h3d opens on page 2. 2. Use the navigations buttons to navigate to Design History on page 1.

Figure 791:

3. In the Results Browser, select the iteration.

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Figure 792:

4. On the Results toolbar, click

to open the Contour panel.

5. Set the Result type: to Shape change (v) and Mag. 6. Click Apply. Shape optimization results are applied to the model.

Figure 793:

Viewing a Contour Plot of the Displacement 1. In the top, right of the application use the navigation buttons to move to page 2.

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2. In the Results Browser, select the last iteration.

Figure 794:

3. On the Results toolbar, open the Deformed panel. 4. Set the Result type: to Shape Change (v). 5. Click Apply. The optimized shape of the beam displays. 6. On the Results toolbar, click

to open the Contour panel.

7. Set the Result type: to Displacement (v) and Mag. 8. Click Apply. 9. On the Annotations toolbar, click

to open the Measures panel.

10. Select Static MinMax Result. Node 1115 has a displacement which is within the constraint value.

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Figure 795:

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OS-T: 5010 Cantilever L-beam Shape Optimization In this tutorial you will perform a shape optimization on an L-section cantilever beam modeled with shell elements. In the schematic, the vertical deflection at point N should be limited to 2.0mm while minimizing the amount of material required.

Figure 796: Cantilever L-Beam Schematic

The optimization problem for this tutorial is stated as: Objective

Minimize mass.

Constraints

A given maximum nodal displacement < 2 mm.

Design Variables

Shape of each of the beam flanges.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Opening the Model 1. Click File > Open > Model.

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2. Select the Lbeamshape.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The Lbeamshape.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Shapes with HyperMorph 1. From the Analysis page, click the optimization panel. 2. Click the HyperMorph panel. 3. Create domains and handles. a) Click the domains panel. b) Select the create subpanel. c) Set the switch to auto functions. d) Click generate. e) Click return to return to the HyperMorph panel. A number of domains and handles are created which will enable us to morph the shape of the beam. There are two types of handles; global handles, which are represented by larger red balls and local handles, which are represented by smaller yellow balls. Only local handles are available in this tutorial. 4. Move handles. a) Click the morph panel. b) Select the move handles subpanel. c) Switch from interactive to translate. d) Using the handles subpanel, select the local handle that is located at the node where the load is applied. Note: Local handles are indicated by a yellow ball. e) In the y val= field, enter -10.0. f) Click morph.

The beam changes shape so that the handle you selected moved -10.0 in the y-direction. Note how the mesh adjusted to this change in shape. 5. Save the shape. a) Select the save shape subpanel. b) In the name= field, enter shape1.

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c) Click color and select a color for the shape. d) Under shape=, select as node perturbations. e) Click save. f) Click Yes to the message regarding the perturbations.

Figure 797:

This shape is saved as shape1. Later, you can associate it to a design variable. 6. Click undo all. The model returns to its original shape. 7. Repeat steps 4 and 5 for the local handles 3, 4 and 5. a) Translate handles 3 and 4 by x=-10 and handle 5 by y=-10. b) Save the shapes after morphing each handle as shape2, shape3 and shape4, respectively.

Figure 798: Handles to be Morphed

8. Click return twice to go to the Optimization panel.

Creating Shape Optimization Design Variables 1. Click the shape panel. 2. Select the desvar subpanel.

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3. Toggle the switch from single desvar to multiple desvars. 4. Using the shapes selector, select shape1, shape2, shape3, and shape4. 5. Click create. 6. Click return to go to the optimization panel. Four shape design variables are created using the shapes that were saved earlier. A potential variation in shape of the vertical flange of the L-beam that could be achieved using the set up described.

Figure 799:

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create the mass response, which is defined for the total volume of the model. a) In the responses= field, enter Mass. b) Below response type, select mass.

c) Set regional selection to total and no regionid. d) Click create. 4. Create the displacement response. a) In the response= field, enter Disp.

b) Below response type, select static displacement. c) Using the nodes selector, select the response node. d) Set the displacement type to dof2. dof1, dof2, dof3

Translation in the X, Y, and Z directions.

dof4, dof5, dof6

Rotation about the X, Y, and Z axes.

total disp

Resultant of the translational displacements in x, y, and z directions.

total rotation

Resultant of the rotational displacements in x, y, and z directions.

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Figure 800:

5. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Click the objective panel. 2. Verify that min is selected. 3. Click response and select mass. 4. Click create. 5. Click return twice to exit the Optimization panel.

Creating Design Constraints 1. Click the dconstraints panel. 2. In the constraint= field, enter constr. 3. Click response = and select Disp.

4. Check the box next to lower bound, then enter -2.0. 5. Using the loadsteps selector, select load. 6. Click create. 7. Click return to go back to the Optimization panel.

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Saving the Database 1. From the menu bar, click File > Save As > Model. 2. In the Save As dialog, enter lbeamshape_opt.hm for the file name and save it to your working directory.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter lbeamshape_opt for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file lbeamshape_opt.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Viewing the Deformed Structure It is helpful to view the deformed shape of a model to determine if the boundary conditions have been defined correctly and also to check if the model is deforming as expected. In this section, use the Deformed panel to review the deformed shape for the last design iteration and a scale factor, and overlay the undeformed shape. 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads .h3d files that contain optimization results on page 2 and analysis results on page 3.

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2. In the top, right of the application, use the navigations buttons to navigate to the Design History (page 2).

Figure 801:

3. In the Results Browser, select the last iteration (iteration 6).

Figure 802:

4. On the Results toolbar, click

to open the Contour panel.

5. Set the Result type: to Shape change (v). 6. Click Apply. The final shape for the Iteration # can now be seen.

Viewing a Transient Animation of the Shape Contour Changes 1. On the Animation toolbar, click

to start the animation.

The seek slider and playback speed slider (top and bottom respectively) are located next to the playback controls.

Figure 803:

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2. Move the speed slider to adjust the animation speed. 3. After reviewing the animation, click

to stop the animation.

4. Move the Current time: back to 0.

Plotting a Displacements Contour 1. In the top, right of the application, click 2. On the Results toolbar, click

to go to page 3, which contains the analysis results.

to open the Contour panel.

3. Set the Result type: to Displacement (v) and Y (Y component of the Displacement, which is what was constrained). 4. In the Results Browser, select the last iteration (iteration 6).

Figure 804:

5. Click Apply. A plot of the displacements on your final shape displays. The maximum displacements for the last Iteration #, is still below 2.0.

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OS-T: 5020 3D Bracket Model using the Free-shape Method In this tutorial you will perform a shape optimization on a solid bracket model using the Free Shape optimization method. The objective of this optimization is to reduce the stress by changing the geometry of the bracket model. The essential idea of free-shape optimization, and where it differs from other shape optimization techniques, is that the allowable movement of the outer boundary is automatically determined, thus relieving users of the burden of defining shape perturbations.

Figure 805:

The optimization problem for this tutorial is stated as: Objective

Minimize (Max von Mises Stress).

Constraints

No Constraints.

Design Variables

Grids move normal to the surface.

Launching HyperMesh and Setting the OptiStruct User Profile 1. Launch HyperMesh. The User Profile dialog appears. 2. Select OptiStruct and click OK. This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

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Opening the Model 1. Click File > Open > Model. 2. Select the free_shape3D.hm file you saved to your working directory from the optistruct.zip file. Refer to Accessing the Model Files. 3. Click Open. The free_shape3D.hm database is loaded into the current HyperMesh session, replacing any existing data. The database only contains geometric data.

Setting Up the Optimization Creating Free-shape Design Variables 1. From the Analysis page, click the optimization panel. 2. Click the free shape panel. 3. In the name= field, enter shape. 4. Using the nodes selector, select the nodes shown in Figure 806. Sselect only the face nodes that are also on shells.

Figure 806: Free-shape Design Space

5. Click create.

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6. Click return to go to the main menu.

Creating Optimization Responses 1. From the Analysis page, click optimization. 2. Click Responses. 3. Create a static stress response. a) In the response= field, enter Stress.

b) Set the response type to static stress. c) Using the props selector, select stress_faces. d) Set the response selector to von mises. e) Under von mises, select both surfaces. f) Click create. 4. Click return to go back to the Optimization panel.

Defining the Objective Function 1. Create an objective reference. a) Click the obj reference panel. b) In the dobjref= field, enter MAX_STR. c) Click response= and select stress.

d) Select pos reference=. A value of 1.0 is assigned by default. e) Click create. f) Click return to go back to the Optimization panel. 2. Define the objective. a) Click the objective panel. b) Select minmax. c) Using the dobjrefs= selector, select MAX_STR. d) Click create. e) Click return to go back to the Optimization panel.

Defining the SHAPE Card Only displacement and stress results are available in the _s#.h3d file by default. In order to look at displacement/stress results on top of a shape change that was applied to the model in HyperView, a SHAPE card needs to be defined. 1. From the Analysis page, click the control cards panel. 2. In the Card Image dialog, click SHAPE.

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3. Set FORMAT to H3D. 4. Set TYPE to ALL. 5. Set OPTION to ALL. 6. Click return twice to go back to the main menu.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Free_Shape3D for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save. The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file Free_Shape3D.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Viewing the Shape Results 1. From the OptiStruct panel, click HyperView. HyperView launches within the HyperMesh Desktop and loads Free_Shape3D_des.h3d file in page 2 and the Free_Shape3D.h3d file in page 3. 2. In the top, right of the application, use the navigations buttons to navigate to the Design History (page 2).

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Figure 807:

3. In the Results Browser, select the last iteration (Iteration 8).

Figure 808:

4. On the Results toolbar, click

to open the Deformed panel.

5. Set the Result type: to Shape change. 6. Click Apply. Shape optimization results are applied to the model.

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Figure 809:

Viewing a Contour Plot of the Stress 1. In the top, right of the application, use the navigations buttons to navigate to the Subcase 1 step (page 3).

Figure 810:

2. In the Results Browser, select the last iteration (iteration 8).

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Figure 811:

3. On the Results toolbar, click

to open the Contour panel.

4. Set the Result type to Element Stresses [2D & 3D]. 5. Set the stress type to von Mises. 6. Click Apply. The stress contour shows on top of the shape changes applied to the model.

Figure 812:

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Setting Up a New Free-shape Optimization Simulation with Moving Constraints In the previous run, no constraints were applied on the movement of the DSHAPE grids. Therefore, grids are free to move and the part thickness increases.

Figure 813: Free-shape Results Without Constraints

In practice, however, there will be some sort of constraints imposed upon the movement of grids due to manufacturability. For this tutorial model, thickness must be unchanged to avoid any interference with other parts. In this step you will define constraints on DSHAPE grids such that the thickness of design space will remain unchanged. The constraints on free-shape design grids will be created separately for curved and flat parts of the design space. The parts of the design space that are grouped as curved and those grouped as flat.

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Figure 814: Design Space On Curved And Flat Part

The constraints on the curved part will be created using a local rectangular coordinate system (the other constraints on the flat part do not need a local coordinate system). Therefore, a local rectangular coordinate system (z-axis will point to normal to DSHAPE surface) needs to be created first. 1. In the top, right of the application, click

/

to move back to Page 1 and the HyperMesh client.

2. In HyperMesh, click return. 3. Define a local coordinate system. a) From the 1D page, click the systems panel. b) Select the create by axis direction subpanel. c) Click nodes > by id, then enter 20999 in the id= field. d) Click origin and enter 20999 in the id= field.

e) Click x-axis and enter 15989 in the id= field.

f) Click xy-plane and enter 19462 in the id= field. g) Click create.

h) Click return.

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Figure 815: Local Coordinate System

4. From the Analysis page, click the optimization panel. 5. Click the free shape panel. 6. Select the gridcon subpanel. 7. Create constraints on the flat part without any coordinate system. a) Click desvar= and select shape. b) Set the constraint type to planar. c) Using the nodes selector, select the nodes shown in Figure 816.

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Figure 816: Constraints On Free Shape Design Space

d) Set the vector definition to vectors. e) Using the N1, N2, and N3 selectors, select the three nodes on plane geometry.

Figure 817: Three Nodes To Defined The Plane

f) Click add. These nodes will move only on the specified plane.

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OptiStruct Tutorials Shape Optimization 8. Create constraints on the curved part using a local coordinate system. a) Set the constraint type to vector. b) Using the nodes selector, select the nodes shown in Figure 818. Only select the nodes that are on the curved part.

Figure 818: Constraints On Free-shape Design Space On Curved Part

c) Set the direction selector to local system, then click the local coordinate system you created. d) Set the vector definition switch to vector. e) Set the direction definition, under vector, to z-axis. f) Click add. 9. Click return twice to get back to the main menu.

Running the Optimization 1. From the Analysis page, click OptiStruct. 2. Click save as. 3. In the Save As dialog, specify location to write the OptiStruct model file and enter Free_Shape3D_const for filename. For OptiStruct input decks, .fem is the recommended extension.

4. Click Save.

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The input file field displays the filename and location specified in the Save As dialog. 5. Set the export options toggle to all. 6. Set the run options toggle to optimization. 7. Set the memory options toggle to memory default. 8. Click OptiStruct to run the optimization. The following message appears in the window at the completion of the job: OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED). OptiStruct also reports error messages if any exist. The file Free_Shape3D_const.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file.

9. Click Close.

Viewing the Results Follow the previously described steps on how to post-process the results (optimization results without constraints) using HyperView, and compare the final shape change and stress results.

Figure 819:

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OS-T: 5030 Buckling Optimization of a Structural Rail In this tutorial, you will perform a size and shape optimization on a structural rail to increase the buckling factor, thereby increasing the load it can carry before buckling. The rail has external forces applied at one end, and is constrained in all degrees of freedom at the other end. By performing buckling optimization, the buckling factor can be increased and thereby increase critical buckling force. Structures are said to "buckle" when a certain combination of loads cause them to be unstable and deflection occurs. When a particular loading is reached, the structure continues to deflect without an increase in the magnitude of the load. The critical load at which buckling occurs is the product of the critical buckling factor and the applied reference load. The buckling factor is an eigenvalue and has no dimension. Generally speaking, the lowest buckling load is usually of the most interest to engineers, since a structure will fail prior to reaching any higher buckling loads. When using OptiStruct to solve a lin