Phased Array Ultrasonic Testing Coursework
Phased Array Ultrasonic Testing
Coursework
NDT44
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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
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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.
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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
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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
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