Quantitative NDE of cellular metallic materials and structures by using eddy current testing technique

The feasibility of Eddy Current Testing (ECT) for the nondestructive evaluation of cellular metallic materials is investigated. The inspection target is focused on the welding joints connecting the surface and inner layers of a typical cellular material - metallic sandwich plate. Through numerical simulations, it is found that the defects in the welding zone cause ECT signals of significant different phase property with those caused by welding bead. The multi-frequency signal processing algorithm (MFA) is used to process the signals in order to improve the S/N ratio, which enables the recognition of crack indication from the mixed signals of welding joint. In addition, through profile reconstruction of a crack in the welding zone by means of a deterministic inverse analysis and MFA, it is demonstrated that ECT is a suitable quantitative NDE technique for the matrix sandwich material.