What is the primary purpose of Magnetic Particle Inspection (MPI)?

Magnetic Particle Inspection (MPI) is primarily used to detect surface and near-surface discontinuities in ferromagnetic materials. This method leverages the magnetic properties of ferromagnetic materials, which become magnetized when subjected to a magnetic field. The presence of defects, such as cracks or inclusions, disrupts the magnetic field, causing localized leakage fields that can attract magnetic particles applied to the surface.

When ferromagnetic materials are tested, magnetic particles—either dry or in suspension—are spread over the surface. If there are any surface or near-surface flaws, the particles congregate at these discontinuities due to the leakage fields, creating visible indications that can be examined under appropriate lighting conditions. Thus, the fundamental purpose of MPI is to identify these defects accurately, ensuring the integrity and reliability of the materials and components being tested.

Understanding this key function highlights why options relating to analysis of composition, measurement of temperature variations, or evaluation of tensile strength do not pertain to the core purpose of MPI, as they fall outside the focus on detecting physical defects in ferromagnetic materials.