Non-Destructive Testing (NDT) Practice Test

Which condition allows for effective magnetic particle inspection?

1. High temperatures

2. Presence of liquid chemicals

3. Magnetic domains aligning

4. Non-ferrous substrates

The correct answer is: Magnetic domains aligning

Magnetic particle inspection (MPI) is an NDT technique primarily used for detecting surface and slightly subsurface defects in ferromagnetic materials. For MPI to be effective, the magnetic domains within the material need to be aligned properly. This alignment allows the magnetic field to effectively penetrate the material and highlight any discontinuities by directing visible particles to the defect areas. When the material is magnetized, the magnetic domains within ferromagnetic materials respond to the applied magnetic field. If there are any defects, such as cracks or voids, the magnetic field will be disrupted, causing the magnetic particles to cluster at these locations. This clustering creates visible indications that can be easily observed and evaluated. Therefore, the condition of magnetic domains aligning is critical for the successful application of magnetic particle inspection.