Semi-analytical computation of a quasi-static field induced by a 3D eddy current probe scanning a 2D layered conductor with parallel rough interfaces

International audienceThis paper deals with the fast computation of the quasi-static fields induced in a conductor with a locally perturbed shape along the longitudinal axis and extruded along the transversal one. Besides, the material is composed of several homogeneous layers with parallel faces. The method used here is based on writing Maxwell's equations in a curvilinear system, which leads to a more simple expression of boundary conditions. The validity of this method for the computation of quasi-static fields induced by an eddy current probe in a conductive half-space with a rough surface has been proved recently, and we propose here to complete this innovative formalism in order to solve an eddy current non-destructive testing (ECNDT) configuration with a rough surface conductive medium composed of several homogeneous layers with parallel faces. This extension allows to tackle new ECNDT configurations such as homogeneous media constituted by rough interfaces. Moreover, it provides sufficient solutions for non-homogeneous conductive parts presenting a depth-varying (i.e., along the direction of the normal local vector with respect to the surface) material property, which can be approximated by a piecewise constant function by introducing multiple thin homogeneous layers