Integrity of piezoceramic patch transducers under cyclic loading at different temperatures

Abstract

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 • 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.

Failure Assessment of Piezoelectric Actuators and Sensors for Increased Reliability of SHM Systems

“…[24][25][26][27][28] pay attention to durability and long-term integrity as well as investigations on typical damage patterns. These investigations include stereomicroscopy [26], monitoring a possible change of the slope of electric charge over strain [26][27][28] and near-field scanning interferometry [24]. These methods are useful under laboratory conditions but cannot be transferred to the inspection of transducers during their employment and operation.…”

Inspection of Piezoceramic Transducers Used for Structural Health Monitoring

“…A PWAS breakage during a test campaign is documented in [ 33 ]. Gall et al present the occurrence of cracks in encapsulated PWAS, caused by mechanical bending loads [ 16 ]. In Figure 1 three different types of breakage are depicted.…”

“…This work focuses on the piezoelectric transducers, which are used as sensors and actuators for active acousto-ultrasonics-based SHM systems. Single types of faults, like effects of the bonding layer, degradation and cracks, have been discussed in [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ] using experimental data or modeling approaches. A detailed analysis for simple transducers with wrap-around electrodes is given in [ 22 ].…”

Materials in machine tool structures

“…Furthermore, piezo ceramics can be applied in a broad dynamic bandwidth. An important aspect when applying these materials is to consider their long-term durability [91]. Fig.…”

“…Charge-strain curves of piezo patch transducer specimen under cyclic fatigue testing at a maximum strain level of 0.3% at room temperature[91].…”