Life-span investigations of piezoceramic patch sensors and actuators

The performance and reliability of piezoceramic patches based on Lead-Zirconate-Titanate (PZT) wafers were investigated under both quasi-static and cyclic loading conditions in sensor and actuator applications. A 4-point bending setup was used to study the patches' loading limits and damage behavior under mechanical tensile and compressive loading at varied strain levels. The patches' performance under electric actuation was tested in a bending actuator setup. As opposed to irreversible damage by cracking of the PZT wafers under tensile loading (strain at failure: ca. 0.35 %), no mechanical damage was observed under compressive loading at strain levels of up to -0.6 %. Instead a partly reversible degradation of the piezoceramic's electromechanical properties was noted. A strain-cycle diagram was established for tensile loading at room temperature. Finite-element analyses were performed using 3D material modeling with electro-mechanical coupling behavior. Very good predictability of the sensor and actuator performance was achieved by FE-simulation. Through numerical investigations the degradation of the patches' sensor performance under tensile loading could be correlated to the increasing number of cracks in the PZT wafers.