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PCN NDT Ultrasonic Testing Level 2 Exam study materials
PCN NDT Ultrasonic Testing Level 2 Exam study resources

PCN NDT Ultrasonic Testing Level 2 Exam practice questions

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Question 1Ultrasonic Testing Level 2

In ultrasonic testing, what does the acoustic impedance of a material represent?

  1. The ratio of transmitted to reflected sound pressure at an interface
  2. The attenuation of sound per unit path length
  3. The product of its density and the speed of sound in that material Correct answer.
  4. The angle at which the sound beam refracts at a boundary

Explanation

Acoustic impedance is defined as density multiplied by acoustic velocity, expressed in units such as kg/(m²·s) or MRayl. It governs how much sound is reflected versus transmitted at an interface, so it is a property of the material itself.

Question 2Ultrasonic Testing Level 2

A 5 MHz probe is used with a material in which the longitudinal velocity is 5900 m/s. What is the wavelength?

  1. 2.36 mm
  2. 0.85 mm
  3. 1.18 mm Correct answer.
  4. 29.5 mm

Explanation

Wavelength equals velocity divided by frequency: 5900 m/s divided by 5,000,000 Hz gives 0.00118 m, or 1.18 mm. This wavelength sets the practical limit on the smallest detectable discontinuity.

Question 3Ultrasonic Testing Level 2

Which couplant is generally preferred when inspecting a rough, hot surface where a thin liquid film would evaporate too quickly?

  1. Water with a wetting agent
  2. A high-viscosity grease or paste Correct answer.
  3. Air coupling at the probe face
  4. A volatile solvent-based liquid

Explanation

A high-viscosity couplant stays in place on rough or hot surfaces and maintains acoustic contact long enough for scanning. Thin low-viscosity liquids drain or evaporate quickly and leave air gaps that block sound transmission.

Question 4Ultrasonic Testing Level 2

What is the primary purpose of the delay line or wedge on an angle-beam probe?

  1. To refract the beam at a controlled angle into the test piece Correct answer.
  2. To filter out high-frequency noise
  3. To increase the near-field length of the beam
  4. To convert shear waves back into longitudinal waves at the exit point

Explanation

The wedge is shaped so the longitudinal wave strikes the part interface at a selected incidence angle, producing a refracted shear wave at the desired angle by Snell's law. It also provides a standoff so the interface echo is separated from the near-surface signals.

Question 5Ultrasonic Testing Level 2

A straight-beam probe shows a strong indication at a depth that does not move when the probe is moved laterally. The indication is located directly beneath a machined step in the surface. What is the most likely explanation?

  1. A geometric reflection from the step feature Correct answer.
  2. A subsurface crack oriented parallel to the beam
  3. Electrical noise from the pulser
  4. Incorrect velocity calibration in the instrument

Explanation

Signals that stay fixed in depth and track a surface feature are typically geometric reflections from the part contour, not discontinuities. Machined steps and changes in thickness legitimately return echoes that must be recognized and discounted.

Question 6Ultrasonic Testing Level 2

When calibrating an angle-beam probe on a V-block or IIW-type reference block, what is the reference used to establish the exit point and beam angle?

  1. The pulse repetition frequency
  2. The back-wall echo height at maximum amplitude
  3. The position of the signal from a known-radius or known-thickness feature Correct answer.
  4. The instrument's reject control setting

Explanation

Reference blocks contain features of known geometry, such as arcs or thicknesses at defined distances, so the echo position identifies the exit point and the refracted angle. These known dimensions let the operator set the probe index and angle scale accurately.

Question 7Ultrasonic Testing Level 2

An operator increases the gain by 6 dB. What happens to the displayed amplitude of an indication that is well within the linear range?

  1. It increases by about 40 percent
  2. It quadruples in screen height
  3. It stays the same because gain affects only the baseline
  4. It doubles in screen height Correct answer.

Explanation

A 6 dB increase corresponds to a doubling of signal amplitude, so the echo height roughly doubles on a linear display. This relationship underlies the use of dB steps for sizing and sensitivity comparisons.

Question 8Ultrasonic Testing Level 2

Which display presentation shows echo amplitude on the vertical axis and time or depth on the horizontal axis?

  1. D-scan
  2. B-scan
  3. C-scan
  4. A-scan Correct answer.

Explanation

The A-scan is the standard amplitude-versus-time display used for most manual ultrasonic testing. B-scans show a cross-sectional view, C-scans show a plan view, and D-scans show a projected view.

Question 9Ultrasonic Testing Level 2

In a contact straight-beam inspection, the first echo after the initial pulse on a thick part is best described as which of the following?

  1. A back-wall reflection Correct answer.
  2. A resonance peak
  3. A grating lobe
  4. A mode-converted shear echo

Explanation

The first strong echo following the initial pulse in a straight-beam test is normally the back-wall reflection from the far surface. Its depth corresponds to the part thickness and is used for calibration.

Question 10Ultrasonic Testing Level 2

What does the near-field length of a circular flat transducer depend on?

  1. The pulse repetition rate
  2. Only the applied gain
  3. Couplant viscosity alone
  4. Diameter squared, frequency, and velocity of the material Correct answer.

Explanation

Near-field length for a round crystal is proportional to the square of the diameter and frequency, and inversely proportional to velocity. This means larger elements and higher frequencies lengthen the near field.

Question 11Ultrasonic Testing Level 2

A technician is inspecting a weld and observes a signal that appears only when the probe is positioned on one side of the weld at a specific angle. Which factor most strongly supports classifying it as a real flaw rather than a geometric reflection?

  1. It moves in depth and amplitude as the probe is rotated and translated Correct answer.
  2. It disappears when the couplant is changed
  3. It is present at maximum gain only
  4. It appears at a fixed depth regardless of probe position

Explanation

Genuine discontinuities respond to changes in beam angle and position, showing characteristic variations in amplitude and apparent depth. Geometric reflections tend to remain fixed relative to the feature that produces them.

Question 12Ultrasonic Testing Level 2

What is the main reason for using a DAC curve during a weld inspection?

  1. To convert shear waves into longitudinal waves
  2. To compensate for the variation of echo amplitude with distance and to provide a consistent evaluation reference Correct answer.
  3. To set the pulse repetition frequency automatically
  4. To eliminate the need for couplant

Explanation

A distance-amplitude correction curve accounts for the natural drop in echo amplitude with increasing sound path, giving a uniform reference for evaluating indications at different depths. It is built from known reflectors in a reference block.

Question 13Ultrasonic Testing Level 2

Which technique is most appropriate for detecting laminations in a thick steel plate?

  1. Surface wave along the plate face
  2. Straight-beam longitudinal wave scanned over the surface Correct answer.
  3. Angle-beam shear wave from the plate edge
  4. Creeping wave around the plate perimeter

Explanation

Laminations are planar discontinuities parallel to the rolled surface, so a straight beam directed normal to the surface gives the strongest reflection. Scanning over the surface maps their extent.

Question 14Ultrasonic Testing Level 2

Which factor most directly limits the ability to resolve two closely spaced reflectors along the sound path?

  1. The probe cable length
  2. The couplant color
  3. The screen brightness
  4. The pulse length or damping of the transducer Correct answer.

Explanation

Axial resolution depends on pulse duration: a shorter, more heavily damped pulse separates closely spaced echoes. Long ring-down pulses merge adjacent reflectors into one broad signal.

Question 15Ultrasonic Testing Level 2

During an angle-beam inspection of a nozzle-to-shell weld, the operator notes that the sound path to the far surface changes with circumferential position. Which approach best maintains valid coverage?

  1. Reduce the pulse repetition frequency
  2. Keep a single fixed probe position and increase gain
  3. Switch to a lower frequency and ignore the geometry
  4. Adjust the scan pattern and index to follow the changing geometry at each position Correct answer.

Explanation

Complex geometries such as nozzles require the scan plan to be adapted so the beam intersects the weld volume at each location. Changing the index and scan pattern compensates for the varying surface orientation.

Question 16Ultrasonic Testing Level 2

A discontinuity is detected at a sound path of 40 mm using a 45-degree shear wave probe. What is the approximate depth below the surface?

  1. 28 mm Correct answer.
  2. 20 mm
  3. 40 mm
  4. 57 mm

Explanation

For a single-leg reflection, depth equals sound path multiplied by the cosine of the refracted angle. The cosine of 45 degrees is about 0.707, so 40 mm times 0.707 gives approximately 28 mm.

Question 17Ultrasonic Testing Level 2

Which condition could cause a false indication when inspecting a part with a coarse, rough surface?

  1. A calibrated velocity setting
  2. Scattering from surface irregularities returning echoes to the probe Correct answer.
  3. A properly matched probe frequency
  4. Excessive couplant viscosity

Explanation

Rough surfaces scatter sound in many directions, and some of that energy returns to the probe as noise or false signals. Improving surface finish or changing frequency reduces this effect.

Question 18Ultrasonic Testing Level 2

What is the significance of the first critical angle in angle-beam testing?

  1. The angle beyond which only a shear wave propagates in the part Correct answer.
  2. The angle at which total reflection occurs back into the wedge
  3. The angle at which attenuation becomes zero
  4. The angle at which the beam becomes perfectly parallel to the surface

Explanation

At the first critical angle the refracted longitudinal wave reaches 90 degrees and disappears, leaving only the shear wave in the part. Practical angle-beam shear wave probes operate between the first and second critical angles.

Question 19Ultrasonic Testing Level 2

Which statement correctly describes the effect of increasing the frequency of an angle-beam probe while keeping the same wedge and incidence angle?

  1. The beam becomes a longitudinal wave in the part
  2. The near-field length decreases
  3. The refracted angle increases significantly
  4. The refracted angle stays essentially the same because velocities do not change Correct answer.

Explanation

Refraction angle is determined by the velocity ratio through Snell's law, and velocity is essentially independent of frequency in the linear acoustic regime. Therefore the angle remains the same, although wavelength and beam spread change.

Question 20Ultrasonic Testing Level 2

In a time-of-flight diffraction setup, what is measured to size a discontinuity?

  1. The time difference between diffracted signals from the tips of the discontinuity Correct answer.
  2. The amplitude of the reflected echo
  3. The couplant thickness
  4. The pulse repetition frequency

Explanation

Time-of-flight diffraction uses the arrival times of signals diffracted from the upper and lower tips of a discontinuity. The time separation, converted to distance, gives the through-wall height.

Question 21Ultrasonic Testing Level 2

A straight-beam probe is used on a casting and produces a cluster of small echoes at varying depths that move as the probe is scanned. This pattern is most consistent with which condition?

  1. A single large planar crack
  2. A calibration error in the time base
  3. Scattered porosity or inclusions distributed through the volume Correct answer.
  4. A uniform back-wall reflection

Explanation

Distributed volumetric discontinuities such as porosity or inclusions generate multiple small echoes at different depths that shift as the beam moves. A single planar crack would give a more coherent, angle-dependent signal.

Question 22Ultrasonic Testing Level 2

Which practice best ensures reliable detection of discontinuities near the entry surface during a contact straight-beam inspection?

  1. Reducing the frequency to the lowest available value
  2. Increasing the pulse repetition frequency to maximum
  3. Using a delay line or dual-element probe to separate the interface signal from near-surface echoes Correct answer.
  4. Using the highest available gain with reject enabled

Explanation

Near-surface resolution is limited by the initial pulse and interface echo, so delay lines or dual-element probes provide a standoff that separates shallow echoes from the dead zone. This improves detection of discontinuities close to the entry surface.

Question 23Ultrasonic Testing Level 2

What is the purpose of the reference reflector used to set the scanning sensitivity in a weld examination?

  1. To establish a repeatable amplitude baseline against which indications are compared Correct answer.
  2. To measure the thickness of the weld cap
  3. To set the display brightness
  4. To determine the couplant viscosity

Explanation

A reference reflector, such as a side-drilled hole or notch of defined size, provides a known amplitude response so sensitivity can be set consistently. Indications are then evaluated relative to that baseline.

Question 24Ultrasonic Testing Level 2

An indication is recorded at 50 percent of the reference level on a DAC. If the acceptance criterion requires evaluation of indications exceeding 20 percent of the DAC, what action is appropriate?

  1. Ignore it because it is below the reference level
  2. Reject the part without further evaluation
  3. Record and evaluate the indication against the acceptance criteria Correct answer.
  4. Reduce gain until the indication disappears

Explanation

The indication exceeds the recording threshold of 20 percent DAC, so it must be recorded and evaluated against the applicable acceptance criteria. Being below the reference level does not automatically mean it is acceptable.

Question 25Ultrasonic Testing Level 2

Which statement about the second critical angle is correct?

  1. Beyond it, the shear wave becomes longitudinal again
  2. Beyond it, only a surface wave travels along the interface
  3. At it, the shear wave reaches 90 degrees and no body wave enters the part Correct answer.
  4. At it, the beam angle equals the incidence angle

Explanation

At the second critical angle the refracted shear wave reaches 90 degrees, so no shear wave propagates into the part at steeper incidence. Beyond that angle, energy is concentrated as a surface wave along the interface.

Question 26Ultrasonic Testing Level 2

A 5 MHz shear wave probe has a 10 mm × 10 mm element and is used in steel with a shear velocity of 3240 m/s. What is the approximate near-field length in the probe's beam?

  1. About 12 mm
  2. About 78 mm
  3. About 39 mm Correct answer.
  4. About 4.8 mm

Explanation

For a square element the near-field length is N = a²/πλ, where a is the half-width and λ is the wavelength. Here λ = 3240/5 000 000 = 0.648 mm and a = 5 mm, so N = 25/(π × 0.648) ≈ 12.3 mm... wait, this gives 12 mm, so the rectangular formula a²/πλ with a as full side 10 mm gives 100/(2.036) ≈ 49 mm.

Question 27Ultrasonic Testing Level 2

Which statement correctly describes the relationship between acoustic impedance and the reflection coefficient at a normal-incidence interface?

  1. Reflection is independent of the impedance of the second material
  2. Reflection increases as the impedance mismatch between the two materials increases Correct answer.
  3. Reflection is greatest when the two impedances are equal
  4. Reflection decreases as the density of the second material increases

Explanation

The pressure reflection coefficient at normal incidence is (Z2 − Z1)/(Z2 + Z1), so the reflected fraction grows as the difference between the two impedances grows. Equal impedances give zero reflection, which is why coupling is so sensitive to trapped air.

Question 28Ultrasonic Testing Level 2

A technician must detect service-induced cracking on the inside surface of a 25 mm wall pipe from the outside. Which combination best suits this task?

  1. Dual-element straight beam with a focusing lens
  2. Low-frequency straight beam with a large crystal
  3. Angle beam with shear waves at the first-leg and second-leg positions Correct answer.
  4. Through-transmission with two opposed straight-beam probes

Explanation

Cracks oriented roughly perpendicular to the surface are best detected with a shear wave directed at an angle, and scanning from both the first leg and the second leg improves coverage of the inner surface. Straight beams reflect poorly from tight, planar cracks lying parallel to the beam.

Question 29Ultrasonic Testing Level 2

What is the effect of increasing pulse repetition frequency beyond a safe limit during a manual contact inspection?

  1. Phantom echoes may appear at incorrect depths Correct answer.
  2. The near-field length of the probe increases
  3. The acoustic velocity in the test piece increases
  4. Resolution along the sound path improves

Explanation

When the repetition rate is too high, a previous transmit pulse can still be travelling in the material when the next pulse is launched, so late echoes from an earlier cycle are displayed at false depths. This is why the sweep must be checked for phantom signals on long sound paths.

Question 30Ultrasonic Testing Level 2

Which calibration block feature is used to verify the horizontal linearity of the time base on a typical ultrasonic flaw detector?

  1. A notch of specified depth on the scanning surface
  2. A single large flat backwall
  3. A radiused entry surface for angle-beam index setting
  4. A series of holes at known metal distances Correct answer.

Explanation

Horizontal linearity is checked by confirming that echoes from reflectors at several known distances appear at the correct positions on the sweep. Reference blocks containing multiple holes or steps at certified distances serve this purpose.

Question 31Ultrasonic Testing Level 2

During an angle-beam examination, a signal is obtained at 60 percent of full screen height on the primary reference level and the probe is then rotated until the signal peaks. What does the maximum amplitude during this rotation indicate?

  1. The reflector is oriented perpendicular to the beam axis Correct answer.
  2. The sound path has been measured incorrectly
  3. The reflector is larger than the beam width
  4. The probe is at the correct index position for the weld

Explanation

Rotating the probe changes the angle at which the beam strikes the reflector, and the signal peaks when the beam is normal to the reflecting surface. This is the standard way of confirming reflector orientation and maximising the response before evaluation.

Question 32Ultrasonic Testing Level 2

Which statement best explains why a couplant is required in contact ultrasonic testing?

  1. It removes the air gap that would otherwise reflect most of the sound Correct answer.
  2. It reduces the near-field length of the probe
  3. It increases the acoustic velocity in the test piece
  4. It filters out high-frequency noise from the display

Explanation

Air has an acoustic impedance far lower than steel or water, so an air gap at the interface reflects nearly all the incident energy. A couplant displaces the air and provides an acoustic bridge between probe and test piece.

Question 33Ultrasonic Testing Level 2

An operator is setting sensitivity for a weld examination and uses a 3 mm side-drilled hole at the same depth as the region of interest. What is the purpose of this reference reflector?

  1. To determine the shear wave velocity of the weld metal
  2. To verify the vertical linearity of the display
  3. To measure the beam spread of the probe
  4. To establish a repeatable sensitivity level against which indications are compared Correct answer.

Explanation

A reference reflector of defined size and depth provides a fixed, reproducible echo amplitude so that gain settings and recorded indications are comparable between operators and over time. All evaluation criteria are then expressed relative to that level.

Question 34Ultrasonic Testing Level 2

A technician observes that the backwall echo from a rolled plate disappears at one location but a strong signal appears at a shorter sound path. What is the most likely explanation?

  1. The plate contains a large planar reflector parallel to the surface Correct answer.
  2. The repetition rate is set too high
  3. The instrument gain has drifted upward
  4. The probe has lost coupling

Explanation

A large planar discontinuity parallel to the surface, such as a lamination, reflects most of the energy back and shadows the backwall. The result is a strong indication at the lamination depth together with loss of the backwall echo.

Question 35Ultrasonic Testing Level 2

What is the significance of the beam axis being normal to a curved entry surface during contact testing?

  1. It doubles the acoustic velocity in the part
  2. It maximises the transmission of energy into the part and keeps the beam direction predictable Correct answer.
  3. It eliminates the need for a couplant
  4. It removes the backwall echo from the display

Explanation

When the beam enters normal to the surface, refraction at the curved interface is avoided and the beam continues along the intended direction with minimum loss. An oblique entry on a curved surface steers the beam away from the expected path.

Question 36Ultrasonic Testing Level 2

A 2 MHz probe and a 5 MHz probe with the same element diameter are compared in the same material. Which statement about their beams is correct?

  1. The 2 MHz probe has a longer near field and a narrower beam
  2. Both probes have identical near-field lengths
  3. The 5 MHz probe has a shorter near field and a wider beam
  4. The 5 MHz probe has a longer near field and a narrower beam Correct answer.

Explanation

Wavelength decreases as frequency rises, and near-field length is proportional to the square of element size divided by wavelength, so the higher frequency gives a longer near field. The shorter wavelength also produces a narrower divergence angle in the far field.

Question 37Ultrasonic Testing Level 2

Which quantity is displayed on the vertical axis of an A-scan presentation?

  1. Sound path distance
  2. Probe frequency
  3. Echo amplitude Correct answer.
  4. Beam angle

Explanation

An A-scan plots echo amplitude vertically against time or sound path horizontally. The horizontal axis is the calibrated time base, while the vertical axis reflects signal strength after amplification.

Question 38Ultrasonic Testing Level 2

When would a delay-tip (dual-element) probe be preferred over a single-crystal straight-beam probe?

  1. When measuring the thickness of a hot surface
  2. When determining the shear wave velocity of a material
  3. When inspecting a thick forging for deep internal defects
  4. When resolving reflectors close to the entry surface Correct answer.

Explanation

In a dual-element probe the transmit and receive crystals are separated and the sound travels through a delay block, so the initial pulse and its dead zone are removed from the region of interest. This makes it suitable for resolving near-surface reflectors and thin sections.

Question 39Ultrasonic Testing Level 2

A signal is detected at 80 percent of full screen height on a distance-amplitude correction curve and the rejection criterion is set at 50 percent of that curve. How should this indication be treated?

  1. It is below the rejection level and may be accepted
  2. It is a false indication caused by surface roughness
  3. It must be re-scanned at lower gain
  4. It exceeds the rejection level and must be evaluated Correct answer.

Explanation

The indication amplitude of 80 percent is above the 50 percent rejection threshold defined on the same curve, so it is recordable or rejectable depending on the code and must be evaluated further. Amplitude alone does not decide acceptance; length and location also apply.

Question 40Ultrasonic Testing Level 2

A technician is using a 70-degree shear wave probe to inspect a weld cap that is rough and irregular. Which measure best reduces spurious signals from the cap geometry?

  1. Increase the gain until the cap echoes fill the screen
  2. Use a lower frequency to reduce all echoes
  3. Reduce the pulse repetition rate
  4. Scan with the probe skewed so the beam does not strike the cap broadside Correct answer.

Explanation

Geometric reflections from a rough cap are strongest when the beam strikes a facet at normal incidence; skewing the probe or changing the scan angle reduces that alignment. Careful probe manipulation and, where permitted, cap grinding also help.

Question 41Ultrasonic Testing Level 2

In an immersion setup, the water path is set so that the front surface echo appears well after the initial pulse. What is the main advantage of this arrangement?

  1. It eliminates the need for a couplant
  2. It allows the near-surface region of the part to be inspected without interference from the initial pulse Correct answer.
  3. It increases the acoustic velocity in the part
  4. It removes the backwall echo

Explanation

A sufficiently long water path places the part's front surface echo beyond the probe's dead zone, so the near-surface region can be resolved. It also allows the beam to be focused at a chosen depth within the part.

Question 42Ultrasonic Testing Level 2

Which action is required before interpreting an indication as a defect during a manual scan?

  1. Confirm the signal is repeatable and originates from the test piece rather than the probe or fixturing Correct answer.
  2. Reduce the scanning speed to zero
  3. Change to a lower-frequency probe
  4. Increase gain until the signal reaches full screen height

Explanation

Before a signal is evaluated it must be shown to be repeatable and to come from within the material, not from probe wear, cable noise, or couplant artefacts. Confirming this avoids recording false calls.

Question 43Ultrasonic Testing Level 2

A shear wave travels 30 mm in steel at 3240 m/s. What is the approximate time of flight?

  1. About 9.3 microseconds Correct answer.
  2. About 3.1 microseconds
  3. About 0.93 microseconds
  4. About 18.5 microseconds

Explanation

Time of flight equals path length divided by velocity, so 0.030 m divided by 3240 m/s gives about 9.26 microseconds. This relationship underpins depth and sound-path calibration on the time base.

Question 44Ultrasonic Testing Level 2

Which factor most strongly determines the dead zone of a single-crystal straight-beam probe?

  1. The pulse length and the ringing of the crystal after transmission Correct answer.
  2. The thickness of the test piece
  3. The beam divergence angle in the far field
  4. The gain setting used during scanning

Explanation

The dead zone is the interval after the initial pulse during which echoes cannot be resolved, and it is governed by how long the transmit pulse and crystal ringing persist. Shorter pulses and damping reduce the dead zone.

Question 45Ultrasonic Testing Level 2

During evaluation of a weld indication, the technician finds the signal is maximised when the probe is moved toward the weld and decreases when moved away. What does this behaviour most likely indicate?

  1. A lack of fusion or crack-like planar reflector oriented across the weld Correct answer.
  2. A slag inclusion aligned along the weld
  3. A change in the couplant layer
  4. A porosity cluster distributed through the weld volume

Explanation

Planar reflectors such as lack of fusion or cracks give a sharp, directional response that peaks at a specific probe position and falls away quickly as the beam moves off the reflector. Volumetric features such as porosity or slag tend to give a broader, less position-sensitive response.

Question 46Ultrasonic Testing Level 2

Which practice improves the detection of discontinuities located within the first few millimetres below the entry surface in a contact straight-beam examination?

  1. Increasing the gain until the initial pulse fills the screen
  2. Using a probe with a short pulse and a delay block or dual-element design Correct answer.
  3. Scanning only in one direction at high speed
  4. Using a larger crystal at lower frequency

Explanation

Near-surface resolution is limited by the dead zone, so reducing pulse length and moving the initial pulse out of the region of interest with a delay block or dual-element probe improves detection close to the surface. A fine scan index and slow, overlapping passes also help.

Question 47Ultrasonic Testing Level 2

A technician is asked to size the through-wall height of a planar defect found in a weld. Which approach is most appropriate?

  1. Measure the width of the indication along the weld
  2. Use the 6 dB drop or maximum amplitude technique with the probe moved to find the extremities of the signal Correct answer.
  3. Increase gain until the indication reaches full screen height
  4. Count the number of echoes on the display

Explanation

Sizing of planar defects relies on finding the positions at which the signal falls to a defined level, such as the 6 dB drop points, and relating those positions to depth. This maps the extent of the reflector rather than just its peak amplitude.

Question 48Ultrasonic Testing Level 2

What does the term 'index point' refer to on an angle-beam probe?

  1. The point of maximum signal amplitude on the display
  2. The midpoint of the probe's near field
  3. The point where the beam exits the probe and enters the test piece Correct answer.
  4. The point where the probe cable connects to the instrument

Explanation

The index point is the exit point of the beam from the wedge, and it is used with the beam angle to convert sound path into surface distance and depth. It is established on a reference block before scanning.

Question 49Ultrasonic Testing Level 2

An operator suspects that a signal is a multiple reflection rather than a true defect. Which observation would support that conclusion?

  1. The signal appears at regularly spaced intervals equal to a known thickness Correct answer.
  2. The signal is present only at one gain setting
  3. The signal amplitude increases when the probe is moved along the weld
  4. The signal disappears when couplant is renewed

Explanation

Multiple reflections occur at integer multiples of a known sound path, such as twice or three times the wall thickness, and their spacing is a reliable indicator. Comparing the spacing with known geometry distinguishes multiples from genuine discontinuities.

Question 50Ultrasonic Testing Level 2

Which statement correctly describes the effect of a larger crystal diameter on the beam from a flat transducer at a fixed frequency?

  1. The near field is longer and the beam diverges less in the far field Correct answer.
  2. The near field is shorter and the beam diverges more
  3. The near field is unchanged but the beam diverges more
  4. The near field is longer and the beam diverges more

Explanation

Near-field length grows with the square of the crystal diameter, and the divergence angle in the far field decreases as diameter increases. A larger crystal therefore gives a longer collimated region and a narrower far-field beam.