Computing methods of hypersingular integral applied to eddy-current testing

The detection of thin-opening cracks is an important part of the eddy-current nondestructive testing (NDT). The integral formulation is well adapted for this modelization if the geometry of the tested piece is simple. However, some integrals involved in the computation contain strong singularities. The aim of this paper is to improve the classical numerical resolution using a general computing method of hypersingular integral.

I. Introduction

Eddy-current testing for the detection of cracks is widely used in the inspection of aeroplanes wings or of tubes in nuclear power plants. A driving coil generates a time-varying field inducing eddy-current in a conducting piece (Fig. 1). A flaw perturbs the eddy-current distribution and, hence, the coil impedance . Numerical methods to solve Maxwell's equations are required to evaluate this perturbation. The field computation is fully three–dimensional (3-D) and reveals important variations of the electromagnetic field near crack [1].