3-D finite element predictions of magnetostatic leakage fields

Traditionally electromagnetic leakage fields have largely been of interest to the designers of electrical machinery and magnetic tape heads. An increasingly important application of such leakage fields, however, relates to their use as a mechanism for the detection of defects in ferromagnetic materials. The finite element simulation of three-dimensional active leakage fields is described, and the theoretical predictions are compared with experimentally obtained leakage field profiles for a rectangular slot in a carbon steel bar. Particular emphasis is placed on techniques for determining boundary conditions and the appropriate excitation current distribution in the bar.