Scanning imaging of composite plate using air-coupled Lamb waves based on probabilistic damage algorithm

Non-contact air-coupled ultrasonic transducers were used to generate pure Lamb wave mode in quasi-isotropic composite plate, the wave mode was used to scan for delamination inspection. In the scanning process, generating and receiving transducers were arranged on the same side of the plate oppositely and obliquely. They were linearly moved synchronously in two orthogonal directions in order to obtain different inspection signals at different positions. Wavelet coefficient envelope signals at certain generating frequency were extracted from the inspection signals in different scanning paths through continuous wavelet transform to image the delamination defects. Based on this, damage index was defined by using probabilistic damage algorithm and damage index of different directions were combined to realize the delamination imaging. Data fusion of imaging results acquired from two orthogonal directions was achieved by using full summation algorithm and full multiplication algorithm. The delamination defect can be well located and reconstructed. Furthermore, a threshold was introduced to the imaging algorithm to improve the location precision and reconstruction quality of the delamination defect.