Accurate baseline-free damage localization in plates using refined Lamb wave time-reversal method

In a recent study, Agrahari and Kapuria (J Int Mater Sys Struct, 27, 1283-1305, 2016) presented a Lamb wave based refined time reversal method (RTRM) for baseline-free damage detection in thin plate structures. In this method, it was proposed to conduct the probe at the frequency of best reconstruction and to use an extended wave packet ranging between two side bands accompanying the main mode of the reconstructed signal for computing the damage index. The method showed excellent sensitivity to damage in a single actuator-sensor path scenario. In the present work, the RTRM is integrated with a damage imaging algorithm called the reconstruction algorithm for probabilistic inspection of defects (RAPID) to develop an accurate baseline-free damage localization technique using a network of piezoelectric wafer patch transducers. Its performance is tested experimentally in an aluminium plate with a block mass damage. It is found that the proposed RTRM conducted at the best reconstruction frequency of the sensor network-plate system is able to predict the damage location with very good accuracy, whereas the other existing baseline-free methods such as the conventional TRM with single mode tuning and the reciprocity principle based method are either ineffective in localizing or give highly erroneous prediction of the damage location.