NDT Discontinuity Interpretation and Evaluation 4

Question 1

A technician finds a UT signal that increases in amplitude as the probe is moved transversely across the weld but does not change when moved along the weld axis. This behavior is most consistent with:

Accepted Answer

A planar discontinuity perpendicular to the beam

Answer

A discontinuity that responds strongly to transverse movement but not axial movement is likely planar and oriented perpendicular to the probe's movement direction.

Question 2

The term 'relevant indication' in NDT means:

Accepted Answer

An indication caused by a genuine discontinuity that must be evaluated against acceptance criteria

Answer

A relevant indication is one caused by an actual discontinuity and must be compared to code acceptance criteria, unlike non-relevant or false indications.

Question 3

A linear porosity chain in a weld is more concerning than isolated pores of equal total area because:

Accepted Answer

Aligned pores reduce effective cross-section and can act as a stress concentrator along a line

Answer

Porosity chains reduce the load-carrying cross-section along a line and the interaction between pores elevates stress concentrations similar to a linear flaw.

Question 4

During liquid penetrant inspection, a rounded indication with a diameter approximately equal to its length is classified as:

Accepted Answer

Rounded

Answer

ASME and AWS codes classify an indication as rounded when its length is equal to or less than three times its width.

Question 5

When sizing a discontinuity by the 6 dB drop method in UT, the probe is moved until the signal amplitude drops to:

Accepted Answer

50% of peak

Answer

The 6 dB drop method moves the probe until the signal falls to half (50%) of its peak amplitude, marking the edge of the reflector.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Discontinuity Interpretation and Evaluation 4