Two-level approach for solving the inverse problem of defect identification in eddy current testing-type NDT

An inverse problem of 3D crack identification inside a conductive material from the eddy current measurements is investigated. 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) methodology. This technique enables to shift the optimization load from a time consuming and accurate model to the less precise but faster coarse surrogate. In this work, the finite element method (FEM) is used as a fine model, while the model based on the volume integral method (VIM) serves as a coarse model. The application of this method to the shape reconstruction allows to shorten the evaluation time that is required to provide the proper parameter estimation of surface defects.