Ultrasonic guided wave imaging of plates containing defects and inclusions

Abstract

This talk 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 actually reconstruct a picture of the plate in terms of weakened areas and material distribution, considering cases with multiple defects of different depths and/or inclusions of different materials. To do so, the minimum-variance distortionless response beamforming processor is applied, using a new set of weights, proposed in [1-2], that improves 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 is further enriched with a scaling of the intensity of the reflection, also based on the physics of the scattered field [3], which enables to assign a grayscale intensity to the pixels, and to distinguish stiffer from weaker areas of the plate.

[1] F. Lanza Di Scalea, S. Sternini, and T. V. Nguyen, “Ultrasonic imaging in solids using wave mode beamforming,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 64, no. 3, pp. 602–616, 2017
[2] S. Sternini, A. Pau, F. Lanza di Scalea “Minimum variance imaging in plates using guided wave mode beamforming, IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol.66 no 12, pp.1906-1919, 2019
[3] A. Pau and D. V. Achillopoulou, “Interaction of shear and Rayleigh- 908 Lamb waves with notches and voids in plate waveguides,” Materials, 909 vol. 10, no. 7, 841, 2017.