FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesEasy
A mechanic needs to perform a nondestructive inspection for surface and near-surface cracks on a steel landing gear axle. Which inspection method magnetizes the part and uses iron particles to reveal defects?
- ALiquid penetrant inspection
- BEddy current inspection
- CUltrasonic inspection
- DMagnetic particle inspection
Show answer & explanationAnswer & explanation
Correct answer: D. Magnetic particle inspection
Magnetic particle inspection magnetizes a ferromagnetic part and applies iron particles that cluster at cracks where the magnetic field leaks, revealing defects. This method only works on ferromagnetic materials such as steel, not on nonmagnetic materials like aluminum or titanium.
Why the other options are wrong
- A. Liquid penetrant relies on dye seeping into surface openings, not magnetism.
- B. Eddy current uses induced electrical currents and works on conductive materials, magnetic or not, but does not use iron particles.
- C. Ultrasonic inspection uses sound waves to detect internal flaws, not magnetism or particles.
Magnetic Particle Inspection (MPI)
A nondestructive test method that magnetizes a ferromagnetic part and applies fine iron particles to reveal surface and near-surface cracks where the particles cluster at flux leakage points.
- Only works on ferromagnetic materials (steel, iron, some nickel alloys)
- Cracks perpendicular to the magnetic field are most detectable
- Part must be demagnetized after inspection
Memory trick: 'Magnets grab iron dust at every crack' - MPI needs ferromagnetic metal