Characterization of Electric Fracture and Fatigue Properties of Advanced Piezoelectric Material Systems

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In most of the applications of sensors and actuators in the field of smart structures and devices, piezoelectric ceramics are subjected to both high mechanical stresses and electric fields hence, it is important for reliability and durability to investigate the fracture and fatigue properties of piezoelectric ceramics and composites under electromechanical loading. In this research project, the electromechanical properties of advanced piezoelectric material systems are investigated. From the theoretical considerations and experimental data for piezoelectric material systems, the following results can be obtained :1. We analyze the electroelastic problems for cracked piezoelectric material systems. The effect of electric field on the fracture mechanics parameters (energy release rate, energy density factor, fatigue crack growth rate) is calculated. We also develop a finite element procedure which allows to compute the polarization switching near the crack tip, and discuss the nonlinear … More fracture properties of piezoelectric material systems.2. (1) We perform the indentation fracture, single-edge precracked-beam, and double torsion tests on piezoelectric ceramics, and discuss the electric fracture properties. We also employ the nonlinear finite element analyses to study the effect of localized polarization switching on the fracture mechanics parameters. (2) We investigate the electric fracture and polarization switching properties of piezoelectric ceramics utilizing the modified small punch technique.3. We perform an experimental and analytical study on the static and cyclic fatigue properties of piezoelectric ceramics under electromechanical loading, using three-point bending method.4. (1) We study the effect of applied voltage on the electroelastic field concentrations ahead of electrodes in piezoelectric actuators. (2) We examine the electromechanical response of piezoelectric bimorphs, and discuss the effects of do electric field and polarization switching on the bending properties. We also present the results on the nonlinear behavior due to domain wall motion for laminated and functionally graded piezoelectric actuators under ac electric field. Less