Discrete non-elliptical probability imaging based on UGWs for anisotropic anti-corrosive structure damage detection of rim-driven thruster

Aiming at health monitoring for anisotropic anti-corrosion structure of rim-driven thruster (RDT), a discrete nonelliptical probability imaging (DNEPI) based on ultrasonic guided waves is proposed. The elliptical location without analytical solution for anisotropic structures is analyzed theoretically. Through reverse thinking, it's avoided by discretization and introducing reference point. Combined with Hausdorff damage sensitivity index (DSI), the damage probability is estimated. All paths' probability is fused and displayed by images. The proposed DNEPI is verified by experiments. The results show that the damage probability energy ratios (Er) of DNEPI (Hausdorff DSI and scattering DSI) and elliptical probability imaging (EPI) are 0.29%, 0.22%, and 0.26% respectively, and improved to 4.55%, 1.89%, and 1.10% with 95% threshold. Compared with EPI, the Er of DNEPI imaging is improved by 3.45%. The robustness of Hausdorff DSI is better than scattering DSI. The proposed DNEPI not only visually presents the damage but also provides higher accuracy.