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Ultrasonic Testing Flashcards

7 cards from real NDT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Ultrasonic Testing flashcards as text

  1. What is the critical angle in ultrasonic testing?

    Answer: The incident angle beyond which total internal reflection occurs and no transmitted longitudinal wave enters the second medium

    The first critical angle is the incident angle at which the refracted longitudinal wave travels at 90° (along the interface), beyond which no refracted longitudinal wave enters the second medium.

  2. What is 'gate' in an ultrasonic testing instrument?

    Answer: An electronic time window set to monitor a specific depth range for signals

    A gate is an electronic time window on the A-scan display that triggers alarms or records signal amplitude when signals appear within the selected time/depth range.

  3. Which pulse duration characteristic has the greatest impact on ultrasonic axial (depth) resolution?

    Answer: Pulse duration (wavelength count in the pulse)

    Shorter pulse duration (fewer wavelengths per burst) gives better axial resolution because two closely spaced reflectors produce distinct, non-overlapping echoes.

  4. In automated ultrasonic testing of pipelines, what scanning pattern is typically used to achieve 100% volumetric coverage?

    Answer: Helical (spiral) scanning pattern

    Helical scanning wraps the transducer path in a spiral around the pipe, ensuring complete 100% volumetric coverage of the weld zone and base material.

  5. Why is a higher frequency ultrasound generally preferred for detecting small flaws?

    Answer: Shorter wavelengths improve sensitivity to small reflectors and enhance resolution

    Higher frequencies have shorter wavelengths, improving both sensitivity (ability to detect small flaws) and axial resolution, because a flaw must be at least half a wavelength to reflect detectable energy.

  6. What is the main limitation of the pulse-echo technique when evaluating a laminar flaw (planar flaw parallel to the test surface)?

    Answer: Normal-beam pulse-echo may not detect laminar flaws if they are below the near-field zone

    Laminar (plate-parallel) flaws in the near-field zone may be difficult to resolve from the entry signal, requiring careful technique or special probes to reliably detect them.

  7. According to ASME codes, when recording UT indications for welds, an indication is typically recordable if its amplitude exceeds what threshold?

    Answer: 50% of the DAC curve

    ASME Section V typically requires recording all indications that exceed 50% of DAC, with further evaluation required for those exceeding 100% DAC.