Silhouette Reconstruction of Sub-surface Defects Based on the Point-source Constrained Partial Differential Equation over the A0-mode Lamb Wave Field

Abstract

Guided elastic waves are used for the non-destructive evaluation of plate-like structures. In recent years, manufacturing based on composites has increased gradually. However, the elastic wave dynamics in such materials is considerably more complicated. The conventional time-of-flight technique is not reliable for locating the defects even in isotropic plates because of the dispersiveness in the Lamb wave propagation. Avoiding difficulties caused by the dispersiveness, this paper proposes a novel imaging method based on the point-source constrained partial differential equation in order to reconstruct the silhouette image of the subsurface defects. A theoretical analysis of the proposed method is developed for single point-like defect in the isotropic plate. Numerical evaluation and several experimental results are presented to verify the image reconstruction process of the subsurface defects in the CFRP plates.