Ultrasonic guided wave imaging of plates containing defects and inclusions

This paper addresses the nondestructive testing of platelike structural components that are widely used in aerospace, marine, and civil structures. The objective is not only to detect and localize possible defects, but to reconstruct a picture of the plate in terms of weakened areas, considering cases with multiple defects of different depths. To do so, the minimum-variance distortionless response (MVDR) beamforming processor is applied, using a new set of weights, that improve the focus of the array by increasing the dynamic range and the spatial resolution of the image. These weights are based on the physics of the propagating Lamb modes, including the symmetric mode S0, the antisymmetric mode A0, and the shear horizontal mode SH0, taking advantage of their compounding too. The beamforming processor intensity enables to distinguish stiffer from weaker areas of the plate.