Influence of cyclic loading and temperature on integrity of piezoceramic patch transducers

In this study the loading limits, damage behavior and long-term integrity of piezoceramic patch transducers, based on monolithic PZT wafers (PIC 255) were investigated. The presented results involve quasi-static and long-term cyclic testing under tensile as well as compressive mechanical loading of the patches, under varied temperatures. Also long-term cyclic electric activation was investigated. A strain-cycle life-span diagram was established for tensile loading at room temperature (RT), +60 °C, +100 °C and -40 °C. In all cases cracking in the PZT ceramic was found to be the relevant failure mechanism which could be correlated to the observed degradation of the patches sensor performance. Preliminary investigations with fracture mechanics methods were carried out on the specimen with fractured PZT wafers. No mechanical damage was found under compressive loading at strain levels of up to -0.6 %. Finite element analyses were performed using 3D material modeling with electromechanical coupling behavior, achieving very good predictability of the sensor and actuator performance. Analytical calculations and numerical simulation were used to interpret experimental findings and also allow the transfer of results to various applications