Integrity of piezoceramic patch transducers under cyclic loading at different temperatures
In this study the loading limits, damage behavior and long-term integrity of piezoceramic patch transducers, based on monolithic PZT (lead zirconium titanate) wafers (PIC 255), were investigated. The study involved quasi-static and long-term cyclic testing under tensile and compressive mechanical loading of the patches, at different temperatures. A strain-cycle lifetime diagram was established for tensile loading at room temperature, and + 60, + 100 and -40 degrees C. In all cases of tensile loading, cracking in the PZT ceramic was found to be the relevant failure mechanism which was shown to be correlated with the observed degradation of sensor performance of the patches. No mechanical damage was found under compressive loading at strain levels of up to -0.6%. Finite element (FE) analyses were performed using 3D material modeling with electromechanical coupling, achieving very good predictability of the sensor and actuator performance. Analytical calculations and numerical simulation were used to interpret experimental findings and to allow the transfer of results to various applications. Based on micro-structural investigations of the cracked PZT wafers and FE simulation, fracture mechanics analyses of the local stress situation in the PZT ceramic were carried out.