Access ASNT NDT Level III Ultrasonic Testing (UT) Questions Bank + Free Mock Exams ASNT NDT Level III Ultrasonic Testing (UT) Practice Quiz - Exam Level Difficulty 1. When a longitudinal wave is incident from a medium with lower acoustic velocity (V1) to one with higher velocity (V2) at an angle below the first critical angle, the refracted angle (θ2) according to Snell's Law will be: Less than the incident angle if mode conversion occurs Equal to the incident angle for shear mode only Greater than the incident angle due to velocity increase Approaching 90 degrees as the incident angle nears the critical value 2. The first critical angle in angle beam UT is defined as the incident angle at which: The refracted shear wave is maximized while longitudinal is minimized The refracted longitudinal wave propagates along the interface at 90 degrees Mode conversion to surface waves begins to dominate The incident wave equals the refracted wave in the second medium 3. The spreading of an ultrasonic beam as it propagates from the transducer, primarily due to diffraction effects, is termed: Attenuation from material absorption Beam divergence in the far field zone Near field interference pattern Geometric focusing from lens curvature 4. The near field (Fresnel zone) length N for a circular transducer is approximated by which formula, where D is diameter and λ is wavelength? N = D λ / 4 N = 4 D / λ N = D² / 4λ N = λ² / D 5. Acoustic impedance (Z) of a material, critical for calculating reflection coefficients at interfaces, is defined as the product of: Frequency and acoustic velocity Wavelength and material density Material density and acoustic velocity Attenuation coefficient and wave frequency 6. In coarse-grained materials such as cast stainless steel, the dominant contributor to ultrasonic attenuation is: Absorption due to internal friction and heat conversion Scattering at grain boundaries and microstructural inhomogeneities Beam divergence in the far field region Mode conversion at phase boundaries 7. In the far field (Fraunhofer zone) of an ultrasonic beam, the sound intensity primarily decreases due to: Constructive interference patterns Material attenuation combined with geometric beam spreading Fluctuations from transducer ringing Increase in wavelength with distance 8. The calculation of the refracted shear wave angle in immersion testing uses Snell's Law, which relates: Incident frequency to refracted wavelength Acoustic impedance mismatch to reflection coefficient Sine of angles to reciprocal velocities in the two media Beam divergence to critical angles 9. The key distinction in particle displacement between longitudinal and shear waves is that in longitudinal waves, displacement is: Perpendicular to propagation with elliptical motion Parallel to propagation but with phase inversion Parallel to the direction of wave propagation Perpendicular but confined to the surface plane 10. Ultrasonic wavelength (λ) is inversely proportional to frequency (f), meaning higher frequency transducers are selected primarily to improve: Penetration through high-attenuation materials Beam divergence in the far field Resolution and sensitivity to small reflectors Near field length for deeper focusing 11. Surface (Rayleigh) waves propagate at a velocity approximately equal to: The longitudinal wave velocity in the material 0.92 to 0.95 times the shear wave velocity Half the shear wave velocity 1.05 times the longitudinal wave velocity 12. The ultrasonic system's capacity to separate two reflectors at similar depths but slightly different lateral positions is known as: Axial resolution, influenced by pulse length Sensitivity, determined by gain settings Lateral resolution, limited by beam width Far field resolution, affected by divergence 13. If the acoustic impedance mismatch between two media is zero (Z1 = Z2), the resulting wave behavior at the interface is: Total reflection with phase inversion Complete transmission without reflection Mode conversion to shear waves only Critical refraction at 90 degrees 14. The V-path configuration in dual-element transducers is designed primarily to: Generate both longitudinal and shear modes simultaneously Minimize dead zone effects for near-surface flaw detection Focus the beam for improved lateral resolution Measure coating thickness through paint layers 15. Instrument linearity in UT encompasses verification of both amplitude response and time base accuracy to ensure: Consistent pulse repetition rate across ranges Accurate flaw sizing and depth measurement Proper gate positioning for automated scanning Stable transducer frequency output 16. For area-amplitude calibration using DAC, the reference reflectors must be: Side-drilled holes of increasing size at constant depth Flat-bottom holes of varying depth with constant size Flat-bottom holes of identical size at different depths Notches oriented perpendicular to the beam path 17. The purpose of conducting a transducer beam profile assessment per ASTM E1065 is to determine: The acoustic velocity in the test material The effective beam dimensions for accurate flaw characterization The time base linearity across the display The transducer's center frequency stability 18. Per ASTM E317 for evaluating UT instrument performance, the acceptable tolerance for vertical linearity is: ±2% of full screen height for high-sensitivity systems ±5% of full screen height across the range ±1 dB over the dynamic range ±10% for amplitude control linearity 19. In the 6 dB drop method for flaw sizing, the flaw boundary is defined at the position where the signal amplitude falls to: 25% of the peak amplitude 50% of the peak amplitude 75% of the peak amplitude 10% of the peak amplitude for precise edges 20. The calibration block most suitable for verifying the exit point and effective angle of an angle beam transducer is: ASTM E164 step wedge block IIW Type 2 or DSC block with radius and holes ASME basic calibration block with SDHs Flat-bottom hole reference block 21. For detecting hydrogen-induced cracking (HIC) in pressure vessels, the most effective UT technique recommended by API 579 is: Angle beam shear wave for volumetric scanning TOFD for precise sizing of stepwise cracking Backscatter or velocity ratio measurement for microstructural changes Phased array for full matrix capture imaging 22. When establishing a DAC curve for weld inspection, the Level III must verify the instrument's: Pulse repetition frequency stability Amplitude linearity prior to calibration Gate threshold for automated alarms Transducer frequency response curve 23. The tandem technique in UT weld inspection is optimized for detecting: Volumetric inclusions in the weld metal Surface-breaking toe cracks Vertical planar flaws like lack of sidewall fusion Transverse cracks perpendicular to the weld axis 24. The DGS (Distance Gain Size) method evaluates flaw size by comparing the echo amplitude to that of: A reference notch at varying depths A spherical void reflector model An equivalent flat-bottom hole reflector A cylindrical side-drilled hole 25. The primary consideration when adjusting the pulse repetition frequency (PRF) in UT is to: Minimize electronic noise from power sources Avoid range ambiguities from overlapping echoes Maximize the transducer's ring-down time Optimize gain for deep penetration 26. For UT of welds in pressure vessels, the acceptance criteria are primarily specified in: ASME Section V for examination methods ASME Section IX for welder qualification ASME Section VIII for construction acceptance ASME Section XI for in-service flaw evaluation 27. ASME Section V Article 4 mandates scanning sensitivity verification at least: Once per day and at job completion At start/end of exam and every 4 hours during Only when changing transducers After detecting a reportable indication 28. In TOFD, flaw height is determined from the time-of-flight difference between: Lateral wave and backwall echo Upper and lower tip diffraction signals Reflected and mode-converted echoes Creeping wave and shear head wave 29. For long-range corrosion screening in thin-walled pipes, the optimal wave mode is: High-frequency shear waves for resolution Longitudinal waves for penetration Guided waves (e.g., Lamb or SH modes) Rayleigh waves for surface sensitivity 30. ASME Section XI for nuclear in-service inspection requires flaw sizing accuracy demonstrated by: ±10% of true flaw depth using tip diffraction Performance demonstration with RMS error limits Calibration to near field length only ±3 dB of reference reflector amplitude 31. Lateral resolution in UT is most directly influenced by: Pulse duration and axial overlap Material attenuation coefficient Effective beam width at the inspection depth Backwall multiple echo separation 32. To accurately locate a flaw's depth in angle beam UT, the Level III must ensure calibration includes the correct velocity for: The couplant layer and wedge material The wedge for index point only The test material's shear or longitudinal mode The calibration block's average velocity 33. In PAUT, focal laws are programmed to adjust element delays for controlling: Pulse repetition frequency and scan speed Probe wedge index and exit point Beam steering angle and focal depth Weld cap geometry compensation 34. A major challenge in immersion testing of thick components using water as couplant is: Excessive mode conversion in the water path Reverberations in the water column overlapping deep echoes Poor impedance match at the water-part interface Inability to generate longitudinal waves in water 35. For high-temperature UT inspections (>150°C), the Level III must compensate for temperature effects on: Beam divergence due to thermal expansion Near field length from frequency shift Acoustic impedance variations only Velocity changes and transducer performance degradation 36. Acoustic emission (AE) monitoring is best suited for detecting: Dormant defects like inclusions without stress Dynamic flaw propagation under applied load Uniform wall thinning from general corrosion Hydrogen blistering in static conditions 37. The damping material in a UT transducer primarily influences: Refraction angle and mode conversion Pulse duration and axial resolution capability Near field length calculation Crystal impedance matching to the wedge 38. For accurate sizing using tip diffraction methods (e.g., TOFD or satellite pulse), the optimal beam incidence for maximum diffraction amplitude from the flaw tip is: Normal to the flaw face for specular reflection Parallel to the flaw plane for mode conversion At the corner trap for amplitude maximization Grazing incidence near the tip edge 39. To enhance lateral resolution in the far field during UT inspections, the Level III should specify a transducer with: Lower frequency for reduced attenuation Acoustic lens or electronic focusing Heavy damping for shorter pulse Larger diameter for longer near field 40. The second critical angle occurs when the incident angle causes the: Longitudinal refracted wave to reach 90 degrees Shear refracted wave to propagate at 90 degrees Surface wave velocity to match shear velocity Total internal reflection without refraction 41. Selecting a higher frequency transducer primarily enhances: Deep penetration in attenuative materials Wider beam spread for broader coverage Detection of small flaws with better resolution Longer near field for surface inspections 42. ASME Section V Article 4 requires that couplant be applied to ensure: No evaporation during long scans Stable probe temperature control Consistent acoustic coupling and transducer mobility Couplant layer thinner than one wavelength 43. To verify horizontal linearity (time base) of a UT instrument, the Level III should use: High-frequency probe for precision Block with multiple known path lengths Single backwall at 80% FSH Electronic simulator only 44. For UT in coarse-grained austenitic stainless steel, the Level III should specify a transducer frequency that is: Higher to enhance flaw resolution Matched to grain size for scattering Lower to reduce scatter attenuation At the critical angle threshold 45. If the near field length N of a 5 MHz, 0.5 inch diameter probe is X inches, doubling the frequency to 10 MHz (same diameter) changes N to: X/2 due to shorter wavelength 4X from squared frequency effect 2X as N ∝ f X/4 from inverse square 46. Calibration blocks for UT must match the test piece in terms of: Tensile strength and microstructure Acoustic velocity and attenuation properties Exact wall thickness and curvature Heat treatment and surface finish only 47. The AWS D1.1 code for structural steel welds primarily employs which UT evaluation method? Tip diffraction for precise sizing TCG with amplitude thresholds 6 dB drop for length assessment DAC with FSH-based discontinuity classes 48. Time Corrected Gain (TCG) differs from DAC in that TCG: Applies only to shear wave inspections Dynamically adjusts gain to flatten the reference curve Requires fewer reference reflectors Is prohibited in ASME codes for welds 49. The use of a delay line in straight beam contact testing is primarily to: Introduce controlled refraction angles Extend the dead zone beyond the test surface Boost the transducer's output frequency Match impedance at the crystal boundary 50. For detecting lamellar tears (parallel to the plate surface) in thick sections, the optimal transducer configuration is: Angle beam shear for skip path coverage Dual-element for near-surface focus Focused immersion for high resolution Normal incidence longitudinal wave Check Answers
