What is magnétoscopie?

Magnetic particle inspection (MPI), also called magnetic particle testing, is a non-destructive testing (NDT) process for detecting surface and shallow subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the part and the magnetic field is formed in the part. Indirect magnetization occurs when no electric current is passed through the part, but a magnetic field is applied from an outside source. The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as ferrous materials. This leakage creates a 'magnetic particle indication' which is visually identified by applying magnetic particles to the surface. The particles are either dry or in a wet suspension.