FEA-based guided wave mode optimization for damage detection on thin-walled structures

Laser imaging technology has been studied to detect defects in plate-like structures over ten years, and acoustic wavenumber spectroscopy (AWS) is one of the most promising methods. This paper describes the performance of AWS for estimating the size of a wall-thinning defect in thin-plate structures by using finite element analysis (FEA). The structure's steady-state response to single-tone ultrasonic excitation is simulated using FEA, and the effect of the wall-thinning defect size on the wavenumber-estimation accuracy is investigated. The A0 guided wave mode has been widely used to observed defects owing to the characteristic that the wave speed increases with increasing plate thickness. However, it is not appropriate for detecting relatively shallow wall-thinning defects, because the rate of change in the wave speed variation with the thickness decreases with the increase in the plate thickness. To overcome this limitation, we propose a method to optimize the excitation frequency and the effective guided wave mode instead of utilizing the A0 mode. The results show that our proposed method is promising for the effective characterization of the size of shallow wall-thinning defects in plate-like structures