What role do magnetic particles play in MPI?

In Magnetic Particle Inspection (MPI), the primary role of magnetic particles is to collect at areas of flux leakage, which helps to reveal defects within the material being tested. MPI works by first magnetizing the object, which creates a magnetic field. When there are any discontinuities, or defects, such as cracks or voids in the material, the magnetic field is disrupted, causing a leakage of magnetic flux at those points.

When magnetic particles (which are often coated with a fluorescent or non-fluorescent medium) are applied to the surface, they are attracted to these areas of leakage. As a result, they congregate at the defect locations, making them visible. This visibility is crucial for inspectors as it allows them to identify potential issues that may affect the integrity of the component. The effectiveness of MPI heavily relies on the properties of these magnetic particles and their ability to accumulate in response to the presence of magnetic field leakages.