Which types of discontinuities can MPI detect?

Magnetic Particle Inspection (MPI) is specifically designed to detect surface and near-surface discontinuities in ferromagnetic materials. The method is highly effective for identifying defects such as cracks, seams, laps, and inclusions, which can compromise the structural integrity of components. These types of defects disrupt the magnetic field in the material, leading to a concentration of magnetic particles at the areas of discontinuity during the inspection process, which becomes visible under suitable lighting conditions.

In contrast, surface color variations may not necessarily indicate a structural defect and are more related to surface finish rather than inherent material integrity, making them undetectable by MPI. Heat distortions pertain to changes in shape due to thermal stresses, which MPI is not designed to identify. Lastly, while wear and corrosion can affect the performance of a material, these types of discontinuities are generally not captured by the MPI method as they may not create the localized magnetic disruption necessary for the detection of particles. Hence, recognizing the specific capabilities of MPI leads to the understanding that it is particularly suited to finding defects like cracks, seams, laps, and inclusions.