Experimental study applying a migration technique in structural health monitoring

This article presents the experimental results of adopting a geophysical migration technique to interpret the ultrasonic flexural wave signals for the purpose of realizing quantitative damage identification in structures. In this study, a homogeneous isotropic plate is examined with a surface-mounted linear array of piezoelectric ceramic (PZT) disk. The piezoelectric disks function as actuators to excite flexural waves and also as sensors to receive the waves scattered from the structural damage in the plate. A prestack reverse-time migration technique, which is an advanced technique in geophysics to reverse the reflection wavefield and to image the Earth's interior, is then used to back-propagate the scattering waves and to image damage in the plate. The configuration of the experimental setup is presented and its capability of accurately generating and receiving flexural waves is validated by comparing the collected signals with an analytical solution of transient response of a narrowband signal in a piezoelectric sensor/actuator integrated plate using Mindlin plate theory. Finally, the migration results from the scattering waves of an artificial damage are presented. It is shown that the existence of the damage is correctly revealed through migration process in the experiment as it has been shown using synthetic data.