NDT Ultrasonic Testing 5

Question 1

What phenomenon is exploited when using Lamb waves (plate waves) in ultrasonic testing?

Accepted Answer

Guided wave propagation through the entire thickness of thin plate structures

Answer

Lamb waves are guided waves that propagate through the full thickness of thin plates or shells, making them effective for long-range screening of large plate areas from a single probe position.

Question 2

In ultrasonic contact testing, what defect orientation is most difficult to detect with a standard normal-beam (0°) transducer?

Accepted Answer

Planar flaws oriented at 45° or parallel to the beam path

Answer

Planar flaws whose faces are parallel to the beam path (vertical cracks) reflect little energy back to a normal-beam transducer, requiring angled beams for reliable detection.

Question 3

What does the term 'signal-to-noise ratio' (SNR) mean in the context of ultrasonic testing?

Accepted Answer

The ratio of flaw signal amplitude to the background material noise level

Answer

SNR compares the flaw echo amplitude to the background 'grass' or noise level; a high SNR means the flaw signal clearly stands out from background noise, enabling reliable detection.

Question 4

When performing ultrasonic thickness measurement on a corroded pipe, which technique is best suited to measure minimum remaining wall thickness through internal corrosion pitting?

Accepted Answer

Multiple-echo technique (echo-to-echo measurement) to ignore coating thickness

Answer

The multiple-echo (echo-to-echo) technique measures between successive back-wall echoes rather than from the front surface, eliminating the influence of coatings or surface irregularities.

Question 5

In full matrix capture (FMC) phased array UT, what data is collected compared to conventional PAUT?

Accepted Answer

The complete A-scan from every transmitter-receiver element combination

Answer

FMC collects a complete A-scan for every possible transmitter-receiver element pair combination, enabling post-acquisition reconstruction (TFM) and far superior imaging flexibility.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Ultrasonic Testing 5