Chuanyao Chen

Effective electromechanical properties of transversely isotropic piezoelectric ceramics with microvoids

In most piezoelectric materials and smart structures, the presence of microvoids can hardly be avoided. In the present paper, detailed three-dimensional (3-D) finite element analyses based on the unit cell method are carried out to investigate the inherent relations between the effective properties and the non-uniform distributions of microscopic electromechanical coupling fields resulting from microvoids. The emphases are placed on the influences of void volume fraction, void distribution, void shape and configuration on the effective properties of voided piezoelectric ceramics. The influences rooting in the permeability of voids and piezoelectricity of matrix materials on the effective properties of voided piezoelectric ceramics are also studied. The results obtained by this study have prospective guiding significances to the structural integrity analyses and fabrication of piezoelectric ceramics.

Modified Schapery's Model for Asphalt Sand

Asphalt sand is described as a viscoelastoplastic materials. To involve elastic, viscoelastic, and viscoplastic strain components, a modified Schapery’s model is proposed through adding a viscoplastic term to the Schapery’s model with elastic and viscoelastic terms, and a strain-hardening model is used to describe viscoplastic behavior. A set of uniaxial compression tests, repeated and simple creep-recovery tests in different stress levels are performed to determine the stress-dependent parameters in the model. Finally, the model is validated by comparison with the results from the uniaxial creep experiments. Better agreement than the Schapery’s model indicates that the modified model is practicable to describe the mechanical behavior of asphalt sand in uniaxial compression.

Interaction between three-dimensional crack and near hard piezoelectric fiber

Abstract Due to intrinsic electromechanical coupling behaviors, various fiber-shaped piezoelectric inhomogeneities (sensor) have been widely applied to detect or arrest the crack and damage in various engineering structures. Knowledge about interaction between three-dimensional (3D) through-thickness crack and near piezoelectric fiber is frequently required for designing various fiber-shaped piezoelectric sensors or actuators. In the present paper, detailed 3D finite element analyses are carried out to probe into the influences of the cylindrical piezoelectric fiber on the 3D crack-tip stress fields. Four main influencing factors, i.e. the ligament length ( δ / ρ ) between the crack-tip and the piezoelectric fiber, the plate thickness ( B / ρ ), the applied mechanical loading, K I , and the electromechanical coupling loading, E 3 e 13 r 0 /K I , are considered. For comparison, deeper investigation on the interaction between the 3D crack and an elastic fiber-shaped inhomogeneity has been also carried out in the current study. The results show clearly that the applied electromechanical loading, E 3 e 13 r 0 /K I , the ligament length, δ / ρ , and plate thickness, B / ρ , have great influence on the interaction between the 3D crack and near piezoelectric fiber. The results obtained by this study have important guiding significances for understanding the interaction mechanism between the 3D crack and the sensor or actuator in a non-piezoelectric elastic matrix.

Analysis for a Piezoelectric Plate Lying over a Viscoelastic Foundation under Cylindrical Bending

Analysis for a piezoelectric plate lying over a viscoelastic foundation under cylindrical bending is presented in this paper. By the method of separating variables, a concise analytical solution for a rectangle piezoelectric plate with viscoelastic restoring force caused by a viscoelastic foundation is obtained. The long-term behavior of the structure is analyzed in detail with a lot of numerical examples. The results show that there exists strain creep together with stress delay when this kind of piezoelectric structure is subjected to mechanical or electric load or electromechanical coupling loads. It is also found from the calculation that when the viscoelastic foundation is made of a Maxwell fluid, the viscoelastic restoring force will gradually attenuate to zero with the passage of time; but when the foundation is a standard viscoelastic solid, the restoring force will always exist along the interface between the piezoelectric plate and the foundation. Moreover, the electric displacement always varies with time during all the loading processes.