Two-level approach for solving the inverse problem of defects identification in Eddy Current Testing – type NDT*

Abstract: This work deals with the inverse problem associated to 3D crack identification inside a conductive material using eddy current measurements. In order to accelerate the time-consuming direct optimization, the reconstruction is provided by the minimization of a last-square functional of the data-model misfit using space mapping (SM) methodo-logy. This technique enables to shift the optimization burden from a time consuming and accurate model to the less precise but faster coarse surrogate model. In this work, the finite element method (FEM) is used as a fine model while the model based on the vo-lume integral method (VIM) serves as a coarse model. The application of the proposed method to the shape reconstruction allows to shorten the evaluation time that is required to provide the proper parameter estimation of surface defects. Key words: defect characterization, electromagnetic inverse problem, two level optimi-zation algorithms, eddy current testing method, sensitivity analysi