Which nondestructive testing method uses magnetic fields and iron particles to reveal flaws?

Which nondestructive testing method uses magnetic fields and iron particles to reveal flaws?

• A. Eddy current inspection
• B. Magnetic particle inspection
• C. Ultrasonic inspection
• D. Radiographic inspection

Answer: (B)

Magnetic particle inspection centers on magnetizing a ferromagnetic part and inspecting the magnetic field for perturbations. When a flaw such as a crack is present, the magnetic flux leaks at that defect. Applying iron particles on the surface causes them to gather at the leakage, forming a visible indication that reveals the flaw. The particles can be dry or suspended in a liquid, and under proper lighting (including fluorescence with a black light) the indication is easy to see. This method is especially sensitive to surface-breaking and near-surface defects and works best on steels, iron, and other ferromagnetic materials. It cannot be used on nonmagnetic metals like aluminum or titanium, and it won’t reveal defects that are deep below the surface. By comparison, eddy current inspection uses induced currents to detect flaws, ultrasonic inspection uses high-frequency sound waves to probe through the material, and radiographic inspection relies on penetrating radiation to image internal features.

Magnetic particle inspection centers on magnetizing a ferromagnetic part and inspecting the magnetic field for perturbations. When a flaw such as a crack is present, the magnetic flux leaks at that defect. Applying iron particles on the surface causes them to gather at the leakage, forming a visible indication that reveals the flaw. The particles can be dry or suspended in a liquid, and under proper lighting (including fluorescence with a black light) the indication is easy to see. This method is especially sensitive to surface-breaking and near-surface defects and works best on steels, iron, and other ferromagnetic materials. It cannot be used on nonmagnetic metals like aluminum or titanium, and it won’t reveal defects that are deep below the surface. By comparison, eddy current inspection uses induced currents to detect flaws, ultrasonic inspection uses high-frequency sound waves to probe through the material, and radiographic inspection relies on penetrating radiation to image internal features.