Effective Damage Detection of Block Mass Type Damage in an Isotropic Plate using a Refined Time-Reversed Lamb Wave Technique
Abstract »In this paper, a recently proposed refined time-reversed Lamb wave method for damage detection is tested experimentally for detecting block mass type damage in isotropic plates. The best reconstruction frequency has been found out for the actuator-plate-sensor system by performing the time reversal process for a certain range of frequency, which is found to be very different from the sweet spot frequency, hitherto recommended for improving the performance of the time-reversal process (TRP) based techniques. Damage indices (DIs) computed by using the conventional main wave packet of the reconstructed signal are less sensitive to an increase in damage size, which is consistent with some recently reported experimental results by other groups. The present method with extended signal length shows excellent sensitivity to damage, and also ensures a low threshold for the undamaged case when used at the best reconstruction frequency. The DIs based on present method reflect the true severity of damage. It was observed that a putty on the plate has no significant change in the DIs, whereas a baseline method would identify it as a damage due to very significant scattering by the putty .