Defect localization in heterogeneous plate structures using the geometric phase change - index of Lamb waves

Defect localization in homogeneous structures using ultrasonic waves is relatively easy to implement. However, locating defects in heterogeneous structures made of different materials can be challenging. This is because complicated reflections, refractions and scatterings occur when ultrasonic waves pass through the interfaces between two dissimilar materials of the heterogeneous structures. To address this issue, a localization methodology based on geometric phase change - index (GPC-I), derived from topological acoustic (TA) sensing, is proposed to adapt to the complicated scenarios when defects are present in heterogeneous plate structures. The GPC-I is adopted as the damage index (DI) to present the possibility of defects appearing on different acoustic sensing paths. A maximum peak value-dependent threshold in GPC-I plots (GPC-I vs. sensor sites) is defined to filter out unreliable sensing paths resulting from the heterogeneity. Different sensing modes (I and II) are combined to comprehensively provide a more reliable and accurate localization framework. Numerical modeling carried out by Abaqus/CAE software verifies the proposed GPC-I based localization technique. Comparison results among GPC-I and other two commonly used acoustic parameters-wave velocity differences (VD) and amplitude ratio (AR) (or wave attenuation) show that the GPC-I has superiority with higher sensitivity and stability for defect localization. This work can provide promising guidance for localizing defects in complex heterogeneous plate structures used in real-world engineering applications.