Thermal analysis of high drive transducer elements

The increasing demand for high-power, low-cost, compact transducer packages for underwater acoustic applications is leading to concerns of overheating in the active driving piezoelectric ceramic (lead zirconate titanate) elements and the associated passive materials (epoxies and polyurethanes). Pushing a design to its thermal limits can lead to reduced acoustic performance and reliability. There is not much guidance to be found in the literature that provides an analytical approach to cope with thermal issues of piezoelectric ceramics in the design phase. An analytic modeling effort is presented that addresses the thermal issues for compact high drive 31-mode free-flooded ring underwater sonar transducers. In this particular case, the thermal issues proved to be the limiting design concerns over the field and stress-limited cases. However, with modeling (analytical and finite element) and bench testing of components, the proper choice of materials and configuration parameters were determined and the performance goals were subsequently achieved. The approach addresses both the transient thermal response and the steady-state temperature profile that results from high-power, high duty cycle drive. These results may prove useful for other similar designs. [Work supported by ONR.]