Which testing method has the disadvantage that the part must be ferrous?

Which testing method has the disadvantage that the part must be ferrous?

• A. Liquid penetrant testing
• B. Magnetic particle inspection
• C. Eddy current testing
• D. Ultrasound testing

Answer: (B)

Magnetic particle inspection relies on magnetizing the part and using a flux leakage field to reveal defects. This technique only works well if the material can be magnetized strongly, which means the part must be ferromagnetic. In ferrous materials, defects disrupt the magnetic field and cause leakage that attracts iron particles, making flaws visible on the surface or just beneath it. That dependency on magnetic properties is what makes this method unsuitable for nonferrous parts like aluminum or copper. Other inspection methods don’t hinge on the material’s ferromagnetism: liquid penetrant testing can detect surface-breaking flaws on a wide range of materials; ultrasound testing uses acoustic waves to probe internal features in many materials; and eddy current testing uses electromagnetic induction to inspect conductivity in conductive parts, including nonferrous ones. So the need for a ferrous material is a distinct limitation of this method, explaining why it’s the correct choice.

Magnetic particle inspection relies on magnetizing the part and using a flux leakage field to reveal defects. This technique only works well if the material can be magnetized strongly, which means the part must be ferromagnetic. In ferrous materials, defects disrupt the magnetic field and cause leakage that attracts iron particles, making flaws visible on the surface or just beneath it.

That dependency on magnetic properties is what makes this method unsuitable for nonferrous parts like aluminum or copper. Other inspection methods don’t hinge on the material’s ferromagnetism: liquid penetrant testing can detect surface-breaking flaws on a wide range of materials; ultrasound testing uses acoustic waves to probe internal features in many materials; and eddy current testing uses electromagnetic induction to inspect conductivity in conductive parts, including nonferrous ones. So the need for a ferrous material is a distinct limitation of this method, explaining why it’s the correct choice.