Eddy current analysis for ECT by BEM utilizing induced currents at 90° edge

In this paper, we study a method to analyze eddy current testing (ECT) by using surface integral equations. When the skin depth is small, the surface integral equations with surface electric and magnetic currents, Js and Ks, as unknowns give accurate solutions. However, the equations are singular at the sharp edge and so, we can’t expect accurate solutions. In ECT, the skin depth is thick, and so the electromagnetic fields are affected strongly by those around the edge. Some edges and corners of the crack are so close that it is difficult to get accurate solutions, moreover, as the width of the crack becomes narrower compared with its depth, the surface integral equations become ill conditioned and so it is more difficult to get accurate results. In order to overcome these problems and get accurate solutions for studying how to get better ECT system, we utilize electromagnetic fields produced by eddy currents at 90° edge in formulating the eddy current. It is assured that the magnetic field is formulated by the surface integral equation for Js even at the edge and corner. To meet boundary condition for Ks at the edge, a semi-linear edge element and a loop magnetic current are introduced in discretization of the surface integral equation. So as to check adequacy of the proposed method, we have solved a typical eddy current problem and confirmed that eddy current problems with a narrow crack can be solved accurately.