Which inspection method is described as limited to surface or near-surface flaw detection?

Which inspection method is described as limited to surface or near-surface flaw detection?

• A. Magnetic particle inspection
• B. Ultrasonic testing
• C. Liquid penetrant testing
• D. Radiographic testing

Answer: (A)

Magnetic particle inspection works by magnetizing a ferromagnetic part and applying iron particles. If a flaw disturbs the magnetic field, the field leaks at the defect and attracts the particles, forming a visible indication right at the surface. This leakage is strongest at the surface or just beneath it, so the method is effectively limited to detecting flaws that are surface-breaking or very near the surface. Deeper internal flaws don’t produce the same surface leakage patterns, so MPI isn’t used for volumetric internal defect detection. This contrasts with methods like ultrasonic or radiographic testing, which probe through the material to reveal internal problems, while liquid penetrant highlights only surface-opening flaws but does so through surface indications as well.

Magnetic particle inspection works by magnetizing a ferromagnetic part and applying iron particles. If a flaw disturbs the magnetic field, the field leaks at the defect and attracts the particles, forming a visible indication right at the surface. This leakage is strongest at the surface or just beneath it, so the method is effectively limited to detecting flaws that are surface-breaking or very near the surface. Deeper internal flaws don’t produce the same surface leakage patterns, so MPI isn’t used for volumetric internal defect detection. This contrasts with methods like ultrasonic or radiographic testing, which probe through the material to reveal internal problems, while liquid penetrant highlights only surface-opening flaws but does so through surface indications as well.