Thermal behavior of high-power active devices with the ATILA (analysis of transducers by integration of LAplace equations) finite-element code

Abstract

Many active devices using piezoelectric ceramics are driven with very high power densities and long pulse lengths. Due to mechanical and dielectric losses in the materials, this produces heat, causing a temperature rise in the devices, which may lead to their mechanical failure. The thermal issues have been shown to be the limiting device design criteria over electric field and mechanical stress limits, yet the effect of the temperature on performance is generally not considered in the numerical models used during the design stage. A coupled electro-mechanical thermal analysis is implemented in the ATILA code. For a steady-state or transient solution, a thermal behavior is weakly coupled to the electromechanical response. The method may take advantage of the order-of-magnitude-greater time constant for thermal effects compared to mechanical behavior. A two-step analysis is performed whereby the electromechanical behavior is first computed, and the resulting dissipated power is then applied as a heat generator to determine the resulting temperature of the device. A high-drive, 31-mode, free flooded ring transducer and a sonar projector serve as validation of the numerical model. The approach addresses both the transient thermal response and the steady temperature profile that results from the high-power, high-duty-cycle drive.