Prestressed curved actuators: characterization and modeling of their piezoelectric behavior

Abstract

Pre-stressed curved actuators consist of a piezoelectric ceramic (lead zirconate titanate or PZT) sandwiched between various substrates and other top layers. The substrates used in this study are stainless steel, and fiberglass. The top layers are made up of aluminum and carbon. Due to their enhanced strain capabilities, these pre-stressed piezoelectric devices are of interest in a variety of aerospace applications. Their performance as a function of electric field, temperature and frequency is needed in order to optimize their operation. During the processing steps, a mismatch between the properties of the various layers leads to pre-stressing of the PZT layer. These internal stresses, combined with restricted lateral motion, are shown to enhance the axial displacement. The goal is to gain an understanding of the resulting piezoelectric behavior over a range of voltages, and frequencies, for unloaded conditions. To quantify the relationship between the state of stress in the ceramic and the overall performance, a physics-based model is developed incorporating both thermo elastic relations and ferroelectric domain theory. The model predicts displacements based on the geometry and physical characteristics of the actuator components. The accuracy of the model and associated numerical method is demonstrated through comparison with experimental data for various input voltages, and boundary conditions.

Degradation of bimorph piezoelectric bending beams in energy harvesting applications

“…This indicates that a possible solution could be to fabricate harvesters where the piezo layers are pre-stressed in compression. This has been successfully exploited in piezo actuator products [46]. Some experimental observations have yet to be fully understood, particularly the higher initial voltages seen consistently in the tensile layers.…”

A stress-dependent hysteresis model for PZT-based transducers

“…Note that (4) does not incorporate ferroelastic coupling so this formulation of the polarization model should be restricted to low stress regimes. As shown in [4,8], the ferroelectric model accurately and efficiently models the field-polarization behavior depicted in Figure 3(a). However, the model does not describe the stress dependent processes including those illustrated in Figures 3(c) and 3(d).…”

“…Stress-biased actuators such as THin layer UNimorph ferroelectric Driver and sEnoR (THUNDER) and Reduced And INternally Biased Oxide Wafer (Rainbow) exhibit enhanced displacements due to a variety of mechanisms including stress-induced domain alignment [7,4,2]. At high stresses, ferroelastic switching must be incorporated into models to maintain the accuracy needed for high-performance applications.…”

A Stress-dependent Hysteresis Model for Ferroelectric Materials

“…where the Gibbs energy is defined by equation (18). To incorporate thermal relaxation, the local average polarization can be calculated by using the thermal evolution model developed in Section 4.1.3.…”