Fundamental understanding of wave generation and reception using d36 type piezoelectric transducers

A new piezoelectric wafer made from a PMN-PT single crystal with dominant piezoelectric coefficient d(36) is proposed to generate and detect guided waves on isotropic plates. The in-plane shear coupled with electric field arising from the piezoelectric coefficient is not usually present for conventional piezoelectric wafers, such as lead zirconate titanate (PZT). The direct piezoelectric effect of coefficient d(36) indicates that under external in-plane shear stress the charge is induced on a face perpendicular to the poled z-direction. On thin plates, this type of piezoelectric wafer will generate shear horizontal (SH) waves in two orthogonal wave propagation directions as well as two Lamb wave modes in other wave propagation directions. Finite element analyses are employed to explore the wave disturbance in terms of time-varying displacements excited by the d(36) wafer in different directions of wave propagation to understand all the guided wave modes accurately. Experiments are conducted to examine the voltage responses received by this type of wafer, and also investigate results of tuning frequency and effects of d(31) piezoelectric coefficient, which is intentionally ignored in the finite element analysis. All results demonstrate the main features and utility of proposed d(36) piezoelectric wafer for guided wave generation and detection in structural health monitoring. (C) 2014 Elsevier B.V. All rights reserved.