Life-span investigations of piezoceramic patch sensors and actuators

Abstract

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 piezoceramics 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

Integrity of piezoceramic patch transducers under cyclic loading at different temperatures

“…In quasi-static tensile testing at RT, it was found that at an average strain level of 0.35% cracks occurred in the PZT wafers (Gall and Thielicke 2007). As the quasi-static testing was continued up to higher strain levels, a growing number of cracks was noted in the visual inspections after each ramp.…”

“…Based on the evaluation of quasi-static and cyclic tensile testing at RT a lifetime diagram characterizing strain-cycle correlations was established by Gall and Thielicke (2007). This diagram was now complemented with the temperaturedependent test data.…”

“…Quasi-static and cyclic testing under compressive mechanical loading at RT was discussed in detail by Gall and Thielicke (2007). Since no additional data is presented here, the results will only briefly be reviewed to complete the information on the behavior of the PZT patches under mechanical loading.…”

“…The current study is a continuation of investigations first presented by Poizat et al (1999) and Thielicke et al (2003), where the use of the 4-point bending test setup was proposed as a simple, but highly effective method to study the sensor performance of piezoelectric composites on various substrates. These studies were extended by Gall and Thielicke (2007), who investigated the long-term integrity of wafer-based PZT patches and presented a lifetime diagram for tensile loading at room temperature (RT).…”

Smart actuation mechanisms for helicopter blades : design case for a Mach-scaled model blade

“…The material tensile strength is significantly lower than its compressive strength [79,80]. As a result, the actuation needs to be asymmetric to use the material to its full capabilities.…”