Guided Wave Piezoelectric Wafer Active Sensor Arrays For Damage Detection

The paper describes an in-situ method for damage detection using phased arrays of piezoelectric wafers active sensors (PWAS) that are permanently attached to the structure. The method uses scanning beams of guided waves that can travel at large distances with little energy loss and hence permit the interrogation of large structural areas from a single location. The novelty of the present method, as different from conventional ultrasonic phased array, consists in use of the unobtrusive and inexpensive permanently attached PWAS to perform interrogation and beamforming as a signal post processing procedure. In order to apply the beamforming theory to guided wave application, a mode tuning technique is employed to obtain the required single mode excitation for the phased array application. After reviewing the principles of the PWAS phased array, its implementation algorithm, the embedded ultrasonic structural radar algorithm (EUSR), is introduced briefly. Based on the developed PWAS phased array beamforming formula, we bring up the practical implementation of PWAS arrays and present analytical and experimental results concerning the omnidirectional damage detection ability. Finally, damage detection on aluminum plates with various PWAS phased arrays is conducted. Results are presented and compared between linear and planar arrays.