Piezoelectric Wafer Active Sensors

Abstract

AbstractEmbedded ultrasonic nondestructive evaluation (NDE) permits active structural health monitoring (SHM), i.e., the on‐demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS). We begin with reviewing the PWAS operational principles. Then the mechanism of using PWAS as guided‐wave transmitters and receivers is presented. PWAS interacts with the host structure through the shear‐lag model. Lamb wave mode tuning can be achieved by the judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. The use of pitch‐catch, pulse‐echo, and phased‐array ultrasonic methods for Lamb wave SHM is addressed. Next, the use of electromechanical (E/M) impedance method with PWAS is described. The local dynamics of the structure can be identified directly through the E/M impedance spectrum of the PWAS permanently mounted to the structure. Simulation studies using analytical and finite element methods are run to predict the structural responses and verified with experimental results. Finally, novel PWAS developments are briefly addressed, including thein situfabricated PWAS and thin‐film PWAS. The article concludes with a discussion on the current status and the future directions for PWAS transducers.