In MPI, what is the significance of flux leakage?

In Magnetic Particle Inspection (MPI), flux leakage is critical because it occurs at discontinuities in the material, such as cracks, laps, or voids. When a ferromagnetic material is magnetized, the magnetic field flows through the material. If there are any defects or discontinuities, the magnetic field lines will be disrupted or "leak" out of the material at those points. This leakage creates a concentration of magnetic flux which can attract magnetic particles applied to the surface.

The ability to detect these disruptions in the magnetic field is fundamental to identifying defects within the material. When magnetic particles accumulate around the areas of flux leakage, they form visible indications that can be observed and evaluated. This characteristic allows inspectors to locate faults that might otherwise go unnoticed, thereby ensuring the integrity of components and structures. Thus, recognizing and understanding flux leakage is essential for effective MPI and enhances the reliability and safety of examined materials.