Electromechanical and fatigue characterization of piezoelectric ceramics.

摘要

This dissertation presents the research conducted on the electro-thermo-mechanical behavior of piezoelectric ceramics for use in actuator applications with an emphasis on ferroelectric fatigue. The material being investigated is a lead zirconate titanate piezoelectric ceramic with the composition PbZr_0.53 Ti_0.47O₃ (PZT-5H). Results presented include an augmented constitutive model that accounts for the temperature dependent piezoelectric properties. Using this model, nonlinear effects measured at one temperature can be extrapolated to other temperatures with good accuracy. An elasticity formulation using a concentric cylinders assemblage to investigate the response of a composite system containing a conservative nonlinear electro-magneto-thermo-mechanical (EMTM) material such PZT-5H is also given. Other material issues including power requirements and generating large strains through the management of domain walls is evaluated. Parametric studies into the electrical and combined electromechanical fatigue of piezoelectric ceramics shows that material degradation is strongly influenced by temperature, waveform of the applied electric field, and applied mechanical loads. Using a finite element model incorporating the proposed constitutive relations along with a domain switching criterion, it is shown that fatigue degradation is caused by large mechanical stresses in the material that arises from dissimilar domains during polarization switching. Methods to increase the fatigue life of piezoelectric ceramics is also presented.