Ultrasonic Testing Principles 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 Principles flashcards as text
In pulse-echo ultrasonic testing, what does the time-of-flight measurement directly indicate?
Answer: The distance from the transducer to the reflector
Time-of-flight is the time for the pulse to travel to the reflector and return; knowing wave velocity allows calculation of distance to the reflector.
What is the critical angle in angle-beam ultrasonic testing?
Answer: The incident angle at which the refracted wave travels along the interface at 90°
The first critical angle is the incident angle at which the refracted longitudinal wave travels exactly along the interface (90° refraction), leaving only a shear wave entering the second medium.
Which scanning method uses a fixed transducer while the part moves, and is commonly used for immersion testing of plates?
Answer: Raster scanning
Raster scanning moves the part (or transducer) in a systematic grid pattern to ensure complete volumetric coverage, commonly used in immersion tank testing.
In immersion ultrasonic testing, what is the recommended water path distance to position the interface echo?
Answer: Greater than the near field length of the transducer
The water path should exceed the near field (Fresnel zone) length so the transducer is operating in the more uniform far field when the beam enters the part.
What does a Distance-Amplitude Correction (DAC) curve compensate for in ultrasonic testing?
Answer: The decrease in signal amplitude from identical reflectors at increasing depths due to beam spread and attenuation
DAC curves account for the natural decrease in echo amplitude from same-size reflectors as depth increases, establishing an amplitude reference that varies with distance.
Rayleigh (surface) waves are most useful for detecting:
Answer: Discontinuities open to or just beneath the surface of a component
Rayleigh waves travel along the surface and penetrate to a depth of approximately one wavelength, making them ideal for detecting surface-breaking or near-surface discontinuities.
The beam spread half-angle of an ultrasonic transducer in the far field is primarily controlled by:
Answer: The ratio of wavelength to transducer active element diameter
Far-field beam divergence is governed by the ratio λ/D (wavelength divided by transducer diameter); larger transducers or higher frequencies produce narrower, more focused beams.