查看更多>>摘要：The classical piezoelectric theory fails to capture the size-dependent electromechanical coupling behaviors of piezoelectric microstructures due to the lack of material length-scale parameters.This study presents the constitutive relations of a piezo-electric material in terms of irreducible transversely isotropic tensors that include material length-scale parameters.Using these relations and the general strain gradient theory,a size-dependent bending model is proposed for a bilayer cantilever microbeam consisting of a transversely isotropic piezoelectric layer and an isotropic elastic layer.Analytical solutions are provided for bilayer cantilever microbeams subjected to force load and voltage load.The proposed model can be simplified to the model incorporating only partial strain gradient effects.This study examines the effect of strain gradient by comparing the normalized electric potentials and deflections of different models.Numerical results show that the proposed model effectively captures size effects in piezoelectric microbeams,whereas simplified models underestimate size effects due to ignoring partial strain gradient effects.
查看更多>>摘要：The electric fatigue load has a significant effect on the crack propagation behavior and failure life of piezoelectric materials and devices.In this paper,an electrical mixed-mode fatigue crack propagation model for piezoelectric materials is proposed based on the piezoelectric Jk-integral theory.The crack initiation,propagation,and life prediction criteria of piezoelectric materials under electric fatigue loading are given by this model,and the finite element simulation model is established to study the electrical mixed-mode crack propagation behavior of piezoelectric structures.Meanwhile,the electrical mixed-mode fatigue crack propagation model is applied to the fatigue crack propagation behavior of a piezoelectric typical defective structure,the crack-hole interference model.The mixed-mode crack propagation,fatigue life,and the interference behavior between the crack and hole at various hole locations of the crack-hole interference model are well recognized by this model.The crack propagation behavior under different electrical load intensities is also considered.The results show that the hole in front of the crack tip inhibits crack propagation to a certain extent,and the strength of electrical load affects the fatigue life of piezoelectric materials and structures.Therefore,the proposed electrical mixed-mode fatigue crack propagation model provides a reference for predicting the mixed-mode fatigue crack propagation behavior and fatigue life of piezoelectric structures under electric fatigue loading.
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