NDT Discontinuity Interpretation and Evaluation 5

Question 1

A technician observes a PT indication that appears only after extended dwell time and is very faint. This behavior is most consistent with:

Accepted Answer

A tight, shallow crack

Answer

Tight cracks hold very little penetrant and produce faint, slow bleed-out indications that require longer dwell times to develop.

Question 2

In radiographic testing, scattered radiation primarily causes:

Accepted Answer

Higher film density and reduced contrast

Answer

Scatter radiation foggs the film uniformly, raising density overall and reducing the contrast needed to detect discontinuities.

Question 3

A stress corrosion crack detected in service differs from a fabrication crack primarily in that it:

Accepted Answer

Typically originates at the surface and is associated with a corrosive environment and tensile stress

Answer

Stress corrosion cracking requires three simultaneous factors — susceptible material, tensile stress, and a corrosive environment — and typically initiates at the surface.

Question 4

During TOFD (Time of Flight Diffraction) inspection, a discontinuity is detected when:

Accepted Answer

Diffracted signals appear between the lateral wave and back-wall signal

Answer

TOFD detects discontinuities by capturing diffracted ultrasonic energy from flaw tips, which appears as additional signals between the lateral wave and back-wall echo.

Question 5

A magnetic particle indication is found on a shaft in an area known to have a geometric stress concentrator (keyway). The inspector should first determine:

Accepted Answer

Whether the indication is relevant or non-relevant

Answer

Geometric features like keyways can produce non-relevant magnetic particle indications due to flux leakage at the geometry change, so relevance must be established first.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Discontinuity Interpretation and Evaluation 5