Discontinuity Interpretation and Evaluation 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 Discontinuity Interpretation and Evaluation flashcards as text
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:
Answer: A planar discontinuity perpendicular to the beam
A discontinuity that responds strongly to transverse movement but not axial movement is likely planar and oriented perpendicular to the probe's movement direction.
The term 'relevant indication' in NDT means:
Answer: An indication caused by a genuine discontinuity that must be evaluated against acceptance criteria
A relevant indication is one caused by an actual discontinuity and must be compared to code acceptance criteria, unlike non-relevant or false indications.
A linear porosity chain in a weld is more concerning than isolated pores of equal total area because:
Answer: Aligned pores reduce effective cross-section and can act as a stress concentrator along a line
Porosity chains reduce the load-carrying cross-section along a line and the interaction between pores elevates stress concentrations similar to a linear flaw.
During liquid penetrant inspection, a rounded indication with a diameter approximately equal to its length is classified as:
Answer: Rounded
ASME and AWS codes classify an indication as rounded when its length is equal to or less than three times its width.
When sizing a discontinuity by the 6 dB drop method in UT, the probe is moved until the signal amplitude drops to:
Answer: 50% of peak
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.
A weld radiograph shows a dark line at the weld toe parallel to the weld edge but outside the weld metal. This is most characteristic of:
Answer: Undercut
Undercut appears as a dark line at the weld toe in the base metal, caused by melting away the base metal that is not refilled by weld metal.
A discontinuity is found in a pressure vessel weld with high fracture toughness material. Compared to a brittle material with the same flaw size, the risk of fracture is:
Answer: Lower because more energy is required to propagate the crack
Higher fracture toughness means more energy is required to propagate a crack, reducing fracture risk for a given flaw size.