NDT Ultrasonic Testing 4

Question 1

What is the critical angle in ultrasonic testing?

Accepted Answer

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

Answer

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.

Question 2

What is 'gate' in an ultrasonic testing instrument?

Accepted Answer

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

Answer

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.

Question 3

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

Accepted Answer

Pulse duration (wavelength count in the pulse)

Answer

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

Question 4

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

Accepted Answer

Helical (spiral) scanning pattern

Answer

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

Question 5

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

Accepted Answer

Shorter wavelengths improve sensitivity to small reflectors and enhance resolution

Answer

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.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Ultrasonic Testing 4