NDT Ultrasonic Testing Principles 3

Question 1

In pulse-echo ultrasonic testing, what does the time-of-flight measurement directly indicate?

Accepted Answer

The distance from the transducer to the reflector

Answer

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.

Question 2

What is the critical angle in angle-beam ultrasonic testing?

Accepted Answer

The incident angle at which the refracted wave travels along the interface at 90°

Answer

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.

Question 3

Which scanning method uses a fixed transducer while the part moves, and is commonly used for immersion testing of plates?

Accepted Answer

Raster scanning

Answer

Raster scanning moves the part (or transducer) in a systematic grid pattern to ensure complete volumetric coverage, commonly used in immersion tank testing.

Question 4

In immersion ultrasonic testing, what is the recommended water path distance to position the interface echo?

Accepted Answer

Greater than the near field length of the transducer

Answer

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.

Question 5

What does a Distance-Amplitude Correction (DAC) curve compensate for in ultrasonic testing?

Accepted Answer

The decrease in signal amplitude from identical reflectors at increasing depths due to beam spread and attenuation

Answer

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.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Ultrasonic Testing Principles 3