Surface crack detection in a thin plate using time reversal analysis of SH guided waves

Ultrasonic nondestructive testing with guided waves is applied for the detection of defects in thin plates. The most important advantage of the application of guided waves is the efficient inspection of structures, such as thin plates and pipes. However, owing to the wave dispersion and wave mode excitability in plates, the wave propagation inside them becomes more complex. Thus, in this study, we developed defect detection for thin plate inspection using guided waves by using the time reversal method, which takes advantage of the reciprocity and reversibility characteristics of waves. However, it is difficult to determine the convergence point of time reversal waves, whose point corresponds to the location of the defect. In this study, the topological sensitivity is utilized as the indicator of defect detection for the time reversal method. In this paper, we first explain the problem to be solved for a scattering problem of 2-D SH guided waves. Next, the forward analysis method for demonstrating scattered wave fields is discussed. Afterwards, a brief description of the time reversal method and the topological sensitivity is introduced. Finally, the topological sensitivity obtained from the forward and time reversal analysis results is calculated to detect surface cracks in thin plates.