Eddy Current Testing (ECT) is a widely used technique in the area of Nondestructive Evaluation. It offers a cheap, fast, non-contact way for finding surface and subsurface defects in a conductive material. Due to development of new designs of eddy current probe coils and advance of model based solutions to inverse problems in ECT, there is an emerging need for fast and accurate numerical methods for efficient modeling and processing of the data. This work contributes to the two directions of computational ECT: eddy current inspection simulation ("forward problem") and analysis of the measured data for automated defect detection ("inverse problem").A new approach to simulate low-frequency electromagnetics in 3D is presented, based on a combination of a frequency-domain reduced vector potential formulation with a boundary condition based on Dirichlet-to-Neumann operator. The equations are solved via a Finite Element Method (FEM), and a novel technique for the fast solution of the related linear system is proposed. The performance of the method is analyzed for a few representative ECT problems. The obtained numerical results are validated against analytic solutions, other simulation codes, and experimental data.The inverse problem of interpreting measured ECT data is also a significant challenge in many practical applications. Very often, the defect indication in a measurement is very subtle due to the large contribution from the geometry of the test sample, making defect detection very difficult. This thesis presents a novel approach to address this problem. The developed algorithm is applied to real problems of detecting defects under steel fasteners in aircraft geometry using 2D data obtained from a raster scan of a multilayer structure with a low frequency eddy current excitation and GMR (Giant Magnetoresistive) sensors. The algorithm is also applied to the data obtained from EC inspection of heat exchange tubes in nuclear power plant.
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