Increasing the scanning range of Lamb wave based SHM systems by optimizing the actuator–sensor design

Abstract

Piezoelectric induced ultrasonic Lamb waves can easily be used for the development of structural health monitoring systems for aircraft and other thin-walled structures. The reduction of the excited wave amplitudes depends mainly on the traveling distance and the material damping, especially in composite materials which restricts the maximum scanning distance between a piezoelectric actuator and a sensor. But there are several possibilities to increase the scanning range of Lamb waves. In the present paper, the focus is on the influence of the adhesive layer and the resonances of the actuator to increase the amplitudes of the excited wave. The objective is to excite Lamb waves with higher amplitudes without increasing the electrical energy for the wave excitation. In the paper, a numerical optimization is proposed which aims at increasing the wave amplitudes by optimizing sensor parameters and the excitation frequency. It has been found that small changes in the geometry of the piezoelectric actuator patch and the use of an optimized excitation frequency elevate the amplitudes of waves significantly.