Magnetic leakage fields from extended inhomogeneities in ferromagnetic plates

The computation of the leakage fields is a very important problem for the magnetostatic detection method of defects in ferromagnetic materials. The computation method which we propose is based on the experimentally very well confirmed assumption, that the leakage flux is negligible compared to the main flux in the ferromagnetic plate. Then the computation of the flux distribution in the plate can be reduced to a 2D problem. The leakage field can be calculated subsequently by using a Dirichlet-Green´s integral. The method allows the determination of the size and permeability of extended defects in plane parallel plates from leakage field measurement data