Damage detection using edge-reflected Lamb waves under modal interference

In the realm of non-destructive testing and health monitoring of plate-shell structures, there is a growing emphasis on ultrasonic Lamb wave testing. Especially, it is imperative to investigate methods for achieving damage detection using a limited number of sensors under modal interference. This study proposes a damage imaging approach that leverages multi-path scattering Lamb waves within a multi-modal framework (i.e., the existing of both A0 mode and S0 mode). The proposed method integrates coded excitation and pulse compression techniques to introduce a damage feature index termed AWLSCC (adaptive weighted local-signal correlation coefficient), which exhibits greater sensitivity compared to the conventional signal amplitude utilized in traditional approaches. Through the alignment of edge-reflected signals with their respective wave packets, this method amplifies the strength of faint reflected wave packets while mitigates potential interferences like modal overlap. Consequently, this technique significantly enhances imaging resolution and accuracy in the identification of cracks in various orientations.