Characterization of damage size in metallic plates using Lamb waves

By employing the Lamb waves for monitoring the structural integrity, a theory was proposed to approximately evaluate the damage size based on the reflection intensity information from the damage. First, to relate the wave reflection intensity to the size and shape of the damage, this theory was constructed for an arbitrary elliptical damage, which can be changed into a crack-like or a circular damage. Then, this theory was verified by employing the numerical results predicted by a powerful numerical approach for through-thickness elliptical holes in aluminum plates. Furthermore, experimental verification was also performed for through-thickness circular holes in aluminum plates. By assuming a damage of a circular shape, this theory was further extended to approximately predict the damage size using a coarse sensor/actuator network after identifying the damage location. To validate the proposed method, a four PZT transducer network was used to experimentally identify the locations and sizes of a circular hole and an elliptical hole in aluminum square plates.