Structural damage imaging based on time-reversal theory for focusing of Lamb waves

Abstract

This study presents a theoretical and experimental investigation of the application of the time-reversed concept to dispersive and multimode Lamb waves for health monitoring of plate-like structures. When a Lamb wave signal is excited in a plate-like structure with damage,the damage will serve as a passive wave source. With the transfer function,the focusing in the time-reversal field composed of distributed transducer network is analyzed by deducing the amplitude expression of the time reversal Lamb wave signals. The result demonstrates that time-reversal signal reaches the maximum amplitude when the observation point is located at the damage location. To validate the focusing effect of the time-reversal method,an efficient imaging method suitable for distributed actuator/sensor networks is adopted for locating and approximate sizing of structural damages. Experimental results combined with finite element simulation illustrate that the inspection energy can be focalized on the damage. It indicates that the time-reversal method is an effective way for identifying and locating damage for Lamb wave inspection.