2.PAUT Coursework [PDF]

Zitiervorschau

Phased Array Ultrasonic Testing Coursework

Phased Array Ultrasonic Testing Coursework

NDT44

NDT44 - 020417

1

Copyright © TWI Ltd.

PAUT Coursework 1

PAUT Coursework 1 1 An ultrasonic longitudinal wave travels in aluminium with a velocity of 635,000 cm/sec and has a frequency of 2 megahertz. The wavelength of this ultrasonic wave is: a b c d

6.35 1.33 6.35 3.17

feet mm mm mm

2 The velocity of sound waves is primarily dependent on : a b c d

The pulse length The frequency of the probe The material in which the sound is being transmitted and the mode of vibration None of the above

3 Angle beam transducers are used to: a b c d

Locate and evaluate discontinuities lying parallel to the surface of the test specimen Locate and evaluate discontinuities that lie parallel to the sound beam Detect discontinuities that are at 90 degrees to the sound beam Detect discontinuities in immersion testing.

4 The process of comparing an instrument or device with a standard is called: a b c d

Angulation Calibration Attenuation Correlation

5 Another name for a compression wave is: a b c d

Lamb wave Shear wave Longitudinal wave Transverse wave

6 A second name for Rayleigh waves is: a b c d

Shear waves Longitudinal waves Transverse waves Surface waves

7 A material used between the face of a search unit and the test surface to permit or improve the transmission of ultrasonic vibrations from the search unit to the material being tested is called: a b c d

A wetting agent A couplant An acoustic transmitter A lubricant

NDT44 - 020417

2

Copyright © TWI Ltd.

PAUT Coursework 1

8 The piezoelectric material in a probe, which vibrates to produce ultrasonic waves, is called: a b c d

A A A A

backing material lucite wedge transducer element or crystal couplant

9 Ultrasonic testing of a material where the probe is in direct contact with the material being tested is: a b c d

Compression wave testing Surface wave testing Angle beam testing All of the above could be performed by contact scanning

10 An advantage of using lithium sulphate in search units is that a b c d

It It It It

is one of the most efficient generators of ultrasonic energy is one of the most efficient receivers of ultrasonic energy is soluble can withstand high temperatures

11 The probe shown in Figure 1 is used for a b c d

Surface wave testing Angle beam testing Immersion testing Straight beam testing

Figure 1 12 Which of the following search units would contain the thinnest transducer element a b c d

A A A A

1-megahertz search unit 5-megahertz search unit 15-megahertz search unit 25-megahertz search unit

NDT44 - 020417

3

Copyright © TWI Ltd.

PAUT Coursework 1

13 Snell’s law can be used to calculate a b c d

Refracted angles Acoustic impedance Frequency All of the above

14 Surface waves can be used to detect defects located a b c d

Close to or at the surface 1 wavelength below the surface 3 wavelengths below the surface At radii

15 When an ultrasonic beam passes through the interface of two dissimilar metals with different velocities at an angle other than 90 degrees, a new angle of sound travel takes place in the second material due to: a b c d

Attenuation Rarefaction Compression Refraction

16 Figure 2 illustrates a contact test on an 80mm aluminium block, using a single crystal 0º compression probe with a calibrated range of 200 mm. A discontinuity is located 60 mm from the front surface and the screen representation for this is shown below. What does indication A represent? a b c d

Initial pulse First discontinuity indication First back surface reflection Mode conversion

Figure 2 17 What does indication B represent in Figure 2? a b c d

Front surface indication First discontinuity indication First back wall reflection None of these

NDT44 - 020417

4

Copyright © TWI Ltd.

PAUT Coursework 1

18 What does indication C represent in Figure 2? a b c d

Second back surface reflection First discontinuity indication Second discontinuity indication First back wall reflection

19 What does indication D represent in Figure 2? a b c d

First discontinuity indication Second indication of the discontinuity First back surface reflection Second back surface reflection

20 What does indication E represent in Figure 2? a b c d

First discontinuity indication Second discontinuity indication First back wall reflection Second back wall reflection

21 Most commercial ultrasonic testing is accomplished using frequencies between a b c d

1 and 25 Kilohertz 0.2 and 20 megahertz 1 and 1,000 kilohertz 15 and 100 megahertz

22 For any given elastic solid which of the following modes of vibration has the greatest velocity? a b c d

Shear wave Transverse wave Surface wave Longitudinal wave

23 Sound waves of a frequency beyond the hearing range of the human ear are referred to as “ultrasonic”. The highest frequency audible to the human ear is about: a b c d

20,000 hertz 2 megahertz 2 kilohertz 200 kilohertz

24 In an A-scan presentation, the horizontal base line represents the: a b c d

Amount of reflected ultrasonic sound energy Distance travelled by the search unit Elapsed time or distance none of the above

25 In an A-scan presentation, the amplitude or height of vertical indications on the screen represents: a b c d

the the the the

amount of ultrasonic sound energy returning to the search unit distance travelled by the search unit thickness of material being treated elapsed time since the ultrasonic pulse was generated

NDT44 - 020417

5

Copyright © TWI Ltd.

PAUT Coursework 2

PAUT Coursework 2 The following questions are related to chapter 1 1 Who is generally given credit for the first ultrasonic phased array system? a b c d

Huygens Jan Somer Kelvin Hughes

2 When using phased array ultrasonics, off-axis beam “artefacts” are a result of: a b c d

destructive interference grating lobes non-uniform voltages applied to separate elements inclusions in the delay wedge

3 In addition to eliminating “ghost images”, eliminating grating lobes also improves _________? a b c d

the signal-to-noise ratio of the main beam acquisition speed dynamic range temporal resolution

4 What aspect of the older analogue systems with high bandwidth, and having large numbers of channels (addressing the large numbers of elements) made manufacturing prohibitive? a b c d

Cutting the wires to the correct length The number of taps required in the delay lines Cross-talk The poor quality of piezo materials available then

The following questions are related to chapter 2 5 What aspect of wave mechanics does a phased array constructed beam rely on? (remember that the best answer is required) a b c d

constructive interference amplitude of waves (i.e. applied voltage) gap between elements damping material used between the elements

6 Who is responsible for the theory used in phased arrays that states that every point on a wavefront may itself be regarded as a source of secondary waves? a b c d

Huygens Fresnel Fermat Fraunhoffer

NDT44 - 020417

6

Copyright © TWI Ltd.

PAUT Coursework 2

7 What is it about the “wavelets” generated by each element on the phased array probe is critical when shaping the beam? a b c d

phase and interaction point with the adjacent wavelet frequency content of the wavelets their acoustic impedance their electrical impedance

8 When two wavefronts of the same amplitude cross through a point in space such that the wave motions are 180° out of phase what is the total displacement of the particle at that point? a b c d

A maximum positive A maximum negative Zero (null displacement) It may be any value depending on the relative amplitudes of the 2 waves

9 In a phased array probe, when a voltage pulse is applied to the piezoelectric material what is the nature of the deformation? a b c d

Torsional Expansion (compression mode) Shear (SH mode) Bending mode

10 Element arrays (64 x 64) with elements having a pitch of approximately 0.25mm are less than 18mm per side. This requires what kind of technology? a b c d

CIVA modelling MEMS (micro-electro-mechanical system) Nano-bots Micro-bots

NDT44 - 020417

7

Copyright © TWI Ltd.

PAUT Coursework 3

PAUT Coursework 3 The following questions are related to chapter 3 1 Given a linear phased array probe, what variable available to the operator limits its near field length? a b c d

frequency voltage to the pulser pulse duration of the pulser voltage number of elements used

2 Given the standard 60 element phased array probe used on pipeline girth welds, what aspect of the phased array probe would be used to increase the position of the near zone for a focal law for an unfocused beam? a b c d

Increase Increase Increase Increase

delay times between adjacent elements the number of adjacent elements used the pulser voltage the receiver amplifier voltage

3 When using the standard 60 element linear array phased array probe what effect on the lateral beam size at the focal spot does a shortening of the focal distance have? a b c d

increases it decreases it no change results in the lateral direction none of the above, it is unpredictable

4 When using a linear 60 element linear array phased array probe what effect on the vertical (longitudinal axis) beam size at the focal spot does a shortening of the focal distance have? a b c d

increases it decreases it no change results in the lateral direction none of the above, it is unpredictable

5 Who is responsible for the theory used in phased array ray-tracing that states that a ray travelling from one point to another will follow a path such that, compared with nearby paths, the time required is a minimum? a b c d

Huygens Fresnel Fermat Fraunhoffer

6 The 32/128 phased array instrument used with 2-60 element phased array probes uses only 120 of the possible electrical connectors on the instrument to address the 2 probes. What are/can the other 8 pulser-receivers be used for? a b c d

dedicated TOFD transverse pair techniques spares all of the above

NDT44 - 020417

8

Copyright © TWI Ltd.

PAUT Coursework 3

7 When a group of focal laws is fired in a sequence with a normal beam wedge, that is simply the same set of delays for a fixed angle repeated by multiplexing the focal law across a group of elements, what is the result called? a b c d

DDF E-scan S-scan M-scan

8 When a group of focal laws is fired in a sequence with delays between adjacent elements altered from one focal law to the next to produce a range of angles, what is the result called? a b c d

DDF E-scan S-scan M-scan

9 When a single focal law is fired to transmit an ultrasonic pulse and then the receiver is adjusted to dynamically change the focal distance as the signal returns to the phased array probe, what is the result called? a b c d

DDF Dyna-scan Deconvolution Signal Averaging

10 Which of the following phased-array probe designs does not allow beam steering?

a 10 element linear array

a b c d

b 4x4 matrix planar array

c 4 element annular array

a b c all three allow beam steering

11 What is the type of phased array scan that uses a series of focal laws multiplexed to duplicate a raster scan (similar to manual scanning)? a b c d

Sectorial Linear or electronic Azimuthal Dynamic depth focusing

12 What is the type of phased array scan that uses a series of focal laws to sweep through a range of angles from a fixed aperture? a b c d

Sectorial Linear Arc Dynamic depth focusing

NDT44 - 020417

9

Copyright © TWI Ltd.

PAUT Coursework 3

13 What is another name for the S-scan? a b c d

Sectorial Azimuthal Linear Both a and b

14 What combination of phased array scan types would be used to examine a point on a radiused curve in the figure below using a 128 element linear array probe with 16 elements in each focal law? The arrows indicate the centre rays of the extremes of the focal laws from one end to the other over the full range of 128 elements.

PA Probe Ray paths

Area of interest

a b c d

Sectorial and Azimuthal Linear and S-scan Azimuthal and dynamic depth focusing None of the above, it cannot be done using phased array scanning

15 A 16/128 PA unit is used to perform a focussed inspection, the 1D linear probe has 64 elements, Calculate the maximum limit of the probes focus with no wedge present in the active plane using a 0° compression wave. Frequency – 5MHz Element width – 0.9mm Gap between elements – 0.1mm Vs – 3.24mm/μs Vc – 5.96mm/μs a b c d

53.7mm 98.8mm 107.4mm 197.5mm

16 Based upon the above probe dimensions which problem may be encountered? a b c d

Cross talk between elements due to gap size Dead elements may occur due to frequency and gap size Grating lobes due to element width E-scanning is not possible due to the PA unit

NDT44 - 020417

10

Copyright © TWI Ltd.

PAUT Coursework 3

17 A Square wave tuneable pulse is to be used to reduce the ring time to a minimum, the nominal frequency of the broad band probe is 4MHz, what will the pulse duration be in order to achieve this? a b c d

125ns 250ns 75ns Square wave pulses cannot be tuned

18 Based upon the probe data in Q15, what will be the Beam diameter for a focused inspection carried out at 50mm focal path (-6dB boundary) a b c d

2.8mm 3.3mm 3.6mm 3.8mm

NDT44 - 020417

11

Copyright © TWI Ltd.

PAUT Coursework 4

PAUT Coursework 4 The following questions are related to chapter 4 1 Phased array systems invariably use a tuneable pulse. Which of the following is not a tuneable pulse form? a b c d

spike tone burst square wave d. all of the above are tuneable Spike pulse

Tone burst pulse

Square wave pulse

2 What is the main benefit of a tuneable pulse? a b c d

Increasing impedance matching Maximising transducer surface displacement (amplitude output) Avoid ringing There are no advantages to a tuneable pulser

3 What ultimately determines the accuracy of the position of a signal in the time gate? a b c d

the encoder the reference target amplitude probe frequency Analogue to Digital digitising frequency

4 If a plan view was plotted with indications exceeding a threshold (typically 5% FSH), represented as a different colour for each 20% increment of depth, we could have a colour-coded depth distribution of flaws. What is the name given to such a display? a b c d

B-scan C-scan Depth-encoded C-scan P-scan

5 What is the dynamic range of a 10-bit digital instrument being used with an unrectified display? a b c d

60dB 54dB 48dB 42dB

NDT44 - 020417

12

Copyright © TWI Ltd.

PAUT Coursework 4

6 Phased-array data displays are better used with TCG than with DAC curves. Why? a b c d

Because evaluation of displays is usually based on amplitude colour-coding More TCG points can be used than are available with DCG points Accept/reject assessments are made using the A-scans TCGs provide better dynamic range and avoid saturating signals

The following questions are related to chapter 5 7 How many horizontal linearity checks must be run on a Phased-array system prior to use? a b c d

1 16 One for each pulser in the unit One for each element that can be addressed by the system

8 How many amplitude control linearity checks must be run on a Phased-array system prior to use? a b c d

1 16 One for each pulser/receiver in the unit One for each element that can be addressed by the system

9 What is the main purpose of delay compensation when using a phased-array probe mounted on a wedge? a b c d

To To To All

correct for echo-transmittance correct for the varying times in the wedge correct for the attenuation due to varying times in the wedge of the above

10 What is the purpose of sensitivity compensation when using a phased-array probe mounted on a wedge? a b c d

To correct for echo-transmittance To correct for the varying times in the wedge To correct for the attenuation due to varying times in the wedge Both a & c are correct

11 Why is a radius used to set sensitivity compensation when configuring focal laws for S-scans instead of other targets? a b c d

Because a SDH provides too low an echo response Because S-scans cannot detect FBHs reliably Both a and b Because it provides a constant soundpath for all focal laws

12 What is the purpose of the radii of SDHs in the phased-array assessment block below? a b c d

To To To To

set range of all focal laws establish resolving and steering limits of the focal laws in a system provide targets on which to compensate for attenuation provide targets on which to compensate for wedge delay

NDT44 - 020417

13

Copyright © TWI Ltd.

PAUT Coursework 4

13 What would be used to assess the steering and resolution limits of an S-scan that was focused along a plane perpendicular to the test surface? a b c d

The end of the IIW block The 100mm radius of the IIW block A series of SDHs at the same depth from the test surface A series of SDHs aligned vertically and at increasing depth to the test surface

14 A “scan-plan” is usually required as part of an inspection procedure when performing a weld inspection. What would this provide? a b c d

Probe standoff position Beam coverage of the weld volume Scan direction (and increment) All of the above should be included

15 When a weld is inspected using S-scans, it is often required to provide scans from two separate stand-offs in addition to requiring scans from both sides of the weld. Why? a b c d

To ensure full volume coverage (especially for thick and wide welds) To ensure each voxel is addressed by multiple beam angles to improve flaw detection Both a and b S-scans should not be used for weld inspection (E-scan is the required technique)

NDT44 - 020417

14

Copyright © TWI Ltd.

PAUT Coursework 4

16 What is the best term to describe the display used in the figure below?

a b c d

An S-scan A volume corrected S-scan A merged side-view azimuthal scan A volume corrected E-scan

17 The Phased array VC-End view represents a 15mm plate section inspected with a 0° encoded compression probe. In order for the phased array equipment to resolve the defect circled the inspection requires

a b c d

Good near surface resolution Good far surface resolution A very low frequency probe A very long ring time

18 In order to provide maximum amplitude the pulse width of 10MHz probe needs to be: a b c d

100ns 200ns 50ns 150ns

NDT44 - 020417

15

Copyright © TWI Ltd.

PAUT Coursework 4

19 Dynamic depth focusing is illustrated below using a 0° compression probe, what is represented by the blue/red symbols:

a b c d

The The The The

red represents the Tx focusing and the blue represents the Rx focusing red represents the Rx focusing and the blue represents the Tx focusing red represents Rx time delay blue represents the Tx time delay

20 The image below was produced to expose laminations in a section of plate utilising several scans, another name for this time of data is:

a b c d

A volumetric merged data scan An electronic gather scan A linear azimuthal scan A batch scan

NDT44 - 020417

16

Copyright © TWI Ltd.

PAUT Coursework 5

PAUT Coursework 5 The following questions are related to chapter 5 1 Dynamic Depth Focusing is a b c d

The ability of equipment to focus a varying depths The multi processing of returned signals to focus at varying depths The ability to move the focal point by changing the shape of the transducer using the Piezo electric properties of the elements. In the PA context it is equivalent to Time Corrected Gain in conventional UT.

2 A Sectorial Scan can be described as a b c d

Uses the same aperture with different focal laws Uses the same focal law with a moving aperture Always uses all elements on a transducer Is derived from combined linear scans

3 In PA terminology, double resolution is a b c d

Doubles the resolution for all scan types Doubles the number samples taken Improves the lateral resolution of a linear scan Is method of reducing file sizes without loss of resolution.

4 Filters on PA equipment a b c d

Improve scan interpretation and can be altered freely Remove background noise without affecting sensitivity Must be used with care to avoid missing relevant indications Can be broadband, narrow band or band pass.

5 The Focal spot during a linear inspection e f g h

Will vary in size during electronic scanning Will remain the same during electronic scanning Focal spot size is only relevant to Sectorial Scans Focal spot size is in the probe parameters in Phase F

6 An Encoder in PA terminology is a b c d

A means of implement data security A means of plotting the mechanical axis A software routine in PhaseFX Is required to run UT studio on a PC.

7 Options for reducing the file size of recorded scans include a b c d

Using less resolution, low PRF, less clock frequency, and more sub-sampling and define the start and stop path Using less resolution, more clock frequency and free scan without an encoder. Use low PRF, low clock frequency, and the ZIP function in user preferences. Set the palette to Black and white, use less resolution, low clock frequency and a low frame rate.

NDT44 - 020417

17

Copyright © TWI Ltd.

PAUT Coursework 5

8 The Focal spot during a Sectorial Scan a b c d

Is constant and referenced to focalisation type. Varies with scan angle because of the change in effective aperture Would vary with effective aperture but this is compensated for by all phased array equipment Will only vary in the passive axis.

The following questions are related to chapter 6 9 What is the 64 element phased array probe imaged below best suited for?

a b c d

Girth weld inspections Immersion testing of turbine blades Acoustic microscopy ERW pipe weld inspections

10 The image below illustrates a modelling of a phased array probe and the intended beam paths to inspect a fastener on an aircraft. What is the “type” of phased array probe imaged below?

a b c d

Rho-theta array 2D matrix array Annular array Circular array

11 Some phased array linear arrays can be configured to carry out TOFD inspections. What is the advantage of PA generated TOFD over single element TOFD? a b c d

Adjustable aperture Adjustable angles to improve resolution Potential to use focused beams for improving tip diffraction sizing resolution All of the above

NDT44 - 020417

18

Copyright © TWI Ltd.

PAUT Coursework 5

12 A tip-diffraction sizing technique was developed using 45° E-scans. What is its advantage over manual techniques using the same principles? a b c d

Speed Uniformity of coupling Computer measurement of displacements and inclinations All of the above

13 Looking at the illustration below define the resolution characteristics required in order to resolve the 2 sets of defects as noted:

B A

a b c d

Set Set Set Set

A/B A/B A/B A/B

require good lateral/axial resolution respectively both require good passive resolution require good Axial/lateral resolution respectively require good active resolution

14 Calculate the maximum limit of focus for a 16 element 1D linear phased array probe without a wedge, given the following parameters: Frequency – 10MHz Pitch – 0.31mm Longitudinal velocity – 5.96mm/μs a b c d

10.3mm 20.6mm 15.3mm 17.3mm

15 Identify from the lists below selections that have a direct bearing on the PA unit focal law calculation and calibrations for a selected probe and wedge a b c d

Focal Focal Focal Focal

depth, depth, depth, depth,

start start start start

element, element, element, element,

ultrasonic range, angular resolution No of elements, sweep range, angular resolution gate positions, sweep range, angular resolution gate positions, ultrasonic range, angular resolution

16 Calculate the beam diameter (-6dB) for the maximum limit of focus in Q14 a b c d

2.52mm 2.26mm 1.26mm 1.16mm

NDT44 - 020417

19

Copyright © TWI Ltd.