This paper presents an approach to reconstruct multiple cracks from eddy current testing signals by means of a stochastic method such as tabu search. The size, number, and locations of cracks are considered unknown in the inversion process, whereas only the orientation of cracks is supposed to be revealed in advance. Eddy current inspections of a stainless steel plate with closely located EDM slits are performed, and the inversions of measured signals are carried out. The results agree well with the true ones, which validates the proposed algorithm

This paper proposes a unique idea for enhancing sizing ability in eddy current nondestructive testing. A detected crack is inspected using several probes driven at the same exciting frequency but producing different eddy current distributions. Two probes are utilized for the purpose in the paper. The crack signals obtained with the two probes are linearly superposed and a unique value of the ratio of superposition is extracted from the mixed signals. Numerical investigations and experimental verification reveal that the value provides clear indications of the crack's depth. In addition, the depth of a notch five times as deep as the standard depth of penetration was well evaluated using the method.