A Multi-Frequency Inversion Algorithm and its Applications in Quantitative NDE of Cracks in Welding Joints of a Metallic Lattice Sandwich Plate

Lattice sandwich metallic plate(LSMP) is a new type of multifunctional material, which is useful in many important industries for its special mechanical behaviors. Cracks in the welding joints of the LSMP may significantly reduce the material strength and, consequently, influence the safety of structure. Up to now, there is still no satisfactory nondestructive evaluation(NDE) method being developed for the quantitative NDE of LSMP. In this paper, an inversion scheme is put forward for the reconstruction of cracks in welding zone from Eddy Current Testing(ECT) signals based on a strategy of multi-frequency inspection. The ECT signals obtained by using a cross-type ECT probe are used to reconstruct profiles of cracks in welding zone. Good consistency of the reconstructed and the true crack profile is obtained, which confirms the validity of the new scheme to NDE of LSMP.