ABSTRACT
The non-destructive testing of highly stressed devices is becoming more and more important for new industrial applications. Therefore, new methods have been developed to identify and locate cracks and other material defects. This chapter presents an analytical method for magnetic field calculation in a non-linear ferromagnetic semi-infinite plate in the presence of eddy currents, magnetized by a short coil wound around the plate. It describes the application of the boundary element method (BEM) technique to 2-D and axisymmetric non-linear magnetic shielding. The major problem in eddy current flaw reconstruction is that the error functional for general 3-D situations may have several local minimums. A first-order optimization strategy may thus give different reconstructed flaws, depending on the initial estimate. The interaction of the eddy current probe with the surface structure can be represented as a convolution of the point spread function with the structure.
