Abstract: Time-reversal Lamb waves combined with a weight distribution imaging algorithm is developed to identify multi-defects in aluminum plate. The wave distortion between the original activated amplitude-modulated pulse and the reconstructed waveform is analyzed to calibrate a time-reversal-based damage index (DI). With a weight distribution function, the calibrated DI values for individual sensing paths are mapped on the discrete ordinates in the inspected area, thus constructing a probability image of the presence of defects. The time-reversibility of Lamb waves and the effectiveness of identifying damage of the time-reversal-based DI is investigated and evaluated in aluminum plates without defect and with different kerf defects (of different lengths) based on dynamic finite element method. An experimental evaluation is conducted for the developed damage identification method. The successful locations of dual kerf defects in an aluminum plate demonstrate that the developed method not only does not rely on the reference signal, but also can accurately identify multi-defects in the aluminum plate.

Key words: injection molding;flow-induced;orientation;end-to-end distance vector;stress distribute;theoretical model, Damage index, Lamb waves, Multi-defects, Time-reversal, Weight distribution function