Investigating the effects of losses of a piezoelectric transducer in temperature varying environment through Finite Element Analysis

Abstract

Piezoelectric ultrasonic transducers are used in many situations, including system and structural health monitoring and for non-destructive testing. For this, a piezoelectric resonator is used to actuate a structure and produce the sound waves that interact with the system under investigation and are then analysed. The behavior of such transducers is dependent on their environment, e.g., on the temperature. The mechanical parameters of the metals can be significantly changed if the temperature modification is large. Furthermore, the piezoelectric materials have their coefficients and losses modified by temperature changes. While the temperature behavior of the piezoelectric and metal can be independently determined experimentally, the role of the temperature change on the transducer performance and generated sound level is not well understood. In this paper, a simple transducer intended for high-temperature applications is investigated using Finite Element Analysis. A piezoelectric disc resonator is glued under a fixed stainless steel membrane, with parameters for the glue considered as those of gold. Effects of losses on the fundamental resonance of the admittance of the transducer and on the sound level it produces are investigated between 20°C and 300°C. Increasing the temperature reduces the resonance frequency of the transducer while maintaining the sound level at resonance. An error of one order of magnitude in input elastic losses of the piezoelectric material will have a stronger effect on the transducer admittance at every frequency than a similar error in the input dielectric and piezoelectric losses.