Discontinuity Interpretation and Evaluation Flashcards

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

Answer: A tight, shallow crack

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

In radiographic testing, scattered radiation primarily causes:

Answer: Higher film density and reduced contrast

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

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

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

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

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

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

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

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:

Answer: Whether the indication is relevant or non-relevant

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.

When comparing a slag inclusion to a crack of the same length in a weld radiograph, the crack is generally more rejectable because:

Answer: Cracks are planar with sharp tips that concentrate stress far more severely than volumetric inclusions

Planar discontinuities like cracks have sharp tips that create extreme stress concentrations, making them structurally more dangerous than volumetric slag inclusions.

A calibration reflector used in UT gives a signal at 80% full-screen height (FSH). A discontinuity signal from the component appears at 60% FSH at the same depth. The indication is:

Answer: Smaller than the calibration reflector and must be evaluated against the applicable acceptance criterion

The 60% FSH signal is smaller than the 80% FSH calibration reflector; whether it is acceptable depends on the code's acceptance criterion relative to that reference.