Influence of temperature on the electromechanical and fatigue behavior of piezoelectric ceramics

This paper describes the results of our numerical and experimental studies of the electromechanical field concentrations due to electrodes in partially poled multilayer piezoelectric film actuators under electric fields. A nonlinear finite element analysis is performed to create the partial poling state through the high electric field and to discuss the electromechanical fields. Displacement versus electric field curves are also measured to validate the numerical predictions, and comparisons are made between numerical results and experimental data. Moreover, the results of the partially poled multilayer actuators are compared with those of fully poled actuators.

We have synthesized cinnamoyl amide type chiral P,olefin ligand and obtained separable diastereomers of 4d and demonstrated Pd-catalyzed asymmetric allylic substitution reactions of indoles using this chiral ligand with high enantioselectivities (up to 98% ee).

This paper studies the dynamic fatigue or slow crack growth in piezoelectric ceramics under electromechanical loading by a combined numerical-experimental approach. Constant load-rate testing was conducted in three-point flexure using the single-edge precracked-beam specimens under zero and positive electric fields, and the effects of electric field and loading-rate on the fracture load and crack propagation were examined. A finite element analysis was also employed to calculate the energy release rate for the permeable, impermeable and open crack models, and the effect of electric field on the energy release rate was discussed. Crack propagation velocity versus energy release rate curves at various loading-rate were then estimated based on the finite element analysis using measured data.

This article discusses the delayed fracture and localized polarization switching near a crack tip in three-point bending piezoceramics under electromechanical loading. We have used finite element analysis to study delayed fracture experiments with single-edge precracked-beam method. A nonlinear finite element analysis was employed to calculate the fracture mechanics parameters such as energy release rate for the permeable, impermeable, and open crack face boundary conditions. Recent proposed energetically consistent boundary conditions were also considered. The effects of applied electric field and localized polarization switching on the fracture mechanics parameters were then examined.