Fast Computation of the Fields Diffracted by a Multi-Layered Conductor With Non-Parallel Rough Interfaces. Application to Eddy-Current Non-Destructive Testing Simulation

This paper deals with the computation of quasi-static fields induced in a conductor by a 3-D eddy-current probe. The shape of the slab is locally distorted and constituted by several homogeneous layers with non-parallel interfaces. The approach is based on writing Maxwell equations in a curvilinear system, leading to a simple analytical expression of boundary conditions. Near every interface, the fields are expanded as sums of eigenfunctions depending on the analytical expression of the 1-D profile describing each interface. Finally, a global S-matrix is computed using a stable recursive algorithm which includes the local change of basis needed for a modal description of the fields in layers presenting non-parallel interfaces. Numerical results are presented and compared with other numerical data.