A Lamb wave time-reversal field reconstruction method for damage detection with automatic focusing determination

This study proposes a wavefield reconstruction method with a time-reversal operation (WR-TR) based on the Lamb wave to detect the damage in the plate. Currently, it is challenging to implement the wavefield reconstruction method for damage detection because of two issues. One is how to quickly simulate the Lamb wavefield. The other is how to determine the focusing time for searching the desired frame from wavefield animation, which can show the location and size of damage. In response, this study introduces a multi-modal superposition finite difference time domain method (MS-FDTD) to simulate the Lamb waves propagation with little calculation cost, which facilitates damage imaging output quickly. In addition, a maximum energy frame method (MEF) is presented to automatically determine the focusing time from wavefield animation, enabling the detection of multiple damage points. The simulations and experiments have demonstrated good noise robustness, anti-distortion ability, and broad applicability with dense or sparse array layouts. Moreover, a detailed comparison between the proposed method and other four Lamb wave-based damage detection methods is evaluated in this paper.