WELD 121 Practice Test

Magnetic Particle Testing relies on magnetizing a ferromagnetic part and spreading iron particles across its surface. When there’s a surface or near-surface flaw, the magnetic flux is disrupted and leaks out around the defect. The iron particles gather at these leakage fields, forming a visible indication that outlines the flaw. This makes MT particularly effective for detecting surface-breaking and near-surface cracks in magnetic materials, and it’s fast, portable, and good for inspecting complex shapes.

This method is different from ultrasonic testing, which uses sound waves; radiographic testing, which uses penetrating radiation; and liquid penetrant testing, which relies on capillary flow of dye to reveal surface openings. The key idea here is the magnetic field creating flux leakage at flaws and the particles rendering that leakage as a visible mark.