Dynamic anti-plane characteristic on an infinite piezoelectric medium with a movable rigid cylindrical inclusion

Scattering and dynamic stress concentrations of time harmonic SH-wave in an infinite elastic piezoelectric medium with a movable rigid cylindrical inclusion are studied in this paper with the help of complex variable and wave function expansion method. The relations that a movable rigid cylindrical inclusion depends on intensity of incident wave and electric field are revealed. The expressions of dynamic stress at the edge of the inclusion are obtained. Numerical calculations are made with different wave numbers and different piezoelectric characteristic parameters. The calculating results show that dynamic stress concentrations at the edge of the inclusion have linear dependence on the incident electric field. And dynamic analyses are very important for an infinite piezoelectric medium with a movable rigid cylindrical inclusion at larger piezoelectric characteristic parameters.

THE ELECTRO-ELASTIC FIELD OF THE INFINITE PIEZOELECTRIC MEDIUM WITH TWO PIEZOELECTRIC CIRCULAR CYLINDRICAL INCLUSIONS

The electro-elastic field of the infinite piezoelectric medium with two piezoelectric circular cylindrical inclusions is derived under the antiplane shear stresses and inplane electric fields.The analytical solution is obtained.The proposed method is based upon the use of conformal mapping and the theorem of analytic continuation.From the results obtained,it can be found that the electro-elastic field depends on the material constants of individual phases,the geometric parameters of the system and the applied antiplane shear stresses and electric fields at infinity.In addition,the specific cases when two circular cylindrical inclusions are tangent to each other and they are holes and/or rigid ones,are also studied in this paper.

Piezoelectric Power Harvesting Process via Phase Changes of Low-Boiling-Point Medium Together with Water for Recovering Low-Temperature Heats

Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures less than 373 K might be at least one of minimum roles for the current generations. Then, piezoelectric power harvesting process for recovering low-temperature heats was invented by using a unique biphasic operating medium of an underlying water-insoluble/low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) in small quantity and upper-layered water in large quantity. The higher piezoelectric power harvesting densities were naturally revealed with an increase in heating temperatures. Excessive cooling of the operating medium deteriorated the power harvesting efficiency. The denser operating medium was surpassingly helpful to the higher piezoelectric power harvesting density. Concretely, only about 5% density increase of main operating medium (i.e. water with dissolving alum at 0.10 mol/dm3) came to the champion piezoelectric power harvesting density of 92.6 pW/dm2 in this study, which was about 1.4 times compared to that with the original biphasic medium of pure water together with a small quantity of NOVEC.

On Propagation of Rayleigh Type Surface Wave in a Micropolar Piezoelectric Medium

In the present paper, the governing equations of a linear transversely isotropic micropolar piezoelectric medium are specialized for x-z plane after using symmetry relations in constitutive coefficients. These equations are solved for the general surface wave solutions in the medium. Following radiation conditions in the half-space, the particular solutions are obtained, which satisfy the appropriate boundary conditions at the stress-free surface of the half-space. A secular equation for Rayleigh type surface wave is obtained. An iteration method is applied to compute the non-dimensional wave speed of the Rayleigh surface wave for specific material parameters. The effects of piezoelectricity, non-dimensional frequency and non-dimensional material constant, charge free surface and electrically shorted surface are shown graphically on the wave speed of Rayleigh wave.

Dynamic anti-plane interaction between an impermeable crack and a circular cavity in an infinite piezoelectric medium

Wave propagation in an infinite elastic piezoelectric medium with a circular cavity and an impermeable crack subjected to steady-state anti-plane shearing was studied based on Green's function and the crack-division technique.Theoretical solutions were derived for the whole elastic displacement and electric potential field in the interaction between the circular cavity and the impermeable crack.Expressions were obtained on the dynamic stress concentration factor(DSCF) at the cavity's edge,the dynamic stress intensity factor(DSIF) and the dynamic electric displacement intensity factor(DEDIF) at the crack tip.Numerical solutions were performed and plotted with different incident wave numbers,parameters of piezoelectric materials and geometries of the structure.Finally,some of the calculation results were compared with the case of dynamic anti-plane interaction of a permeable crack and a circular cavity in an infinite piezoelectric medium.This paper can provide a valuable reference for the design of piezoelectric actuators and sensors widely used in marine structures.

A MIXED ELECTRIC BOUNDARY VALUE PROBLEM FOR AN ANTI-PLANE PIEZOELECTRIC CRACK

The analytical continuation method is adopted to solve a mixed electric boundary value problem for a piezoelectric medium under anti-plane deformation.The crack face is partly conductive and partly impermeable.The results show that the stress intensity factor is identical with the mode Ⅲ stress intensity factor independent of the conducting length.But the electric field and the electric displacement are dependent on the electric boundary conditions on the crack faces and are singular not only at the crack tips but also at the junctures between the impermeable part and conducting portions.

APPLICATION OF TREFFTZ BEM TO ANTI-PLANE PIEZOELECTRIC PROBLEM

Anti-plane electroelastic problems are studied by the Trefftz boundary element method （BEM） in this paper. The Trefftz BEM is based on a weighted residual formulation and indirect boundary approach. In particular the point-collocation and Galerkin techniques, in which the basic unknowns are the retained expansion coefficients in the system of complete equations, are considered. Furthermore, special Trefftz functions and auxiliary functions which satisfy exactly the specified boundary conditions along the slit boundaries are also used to derive a special purpose element with local defects. The path-independent integral is evaluated at the tip of a crack to determine the energy release rate for a mode Ⅲ fracture problem. In final, the accuracy and efficiency of the Trefftz boundary element method are illustrated by an example and the comparison is made with other methods.

INTERACTION OF A SCREW DISLOCATION WITH AN INTERFACIAL EDGE CRACK IN A TWO-PHASE PIEZOELECTRIC MATERIAL

The interaction of a screw dislocation with an interracial edge crack in a two-phase piezoelectric medium is investigated.Closed-form solutions of the elastic and electrical fields induced by the screw dislocation are derived using the conformal mapping method in conjunction with the image principle.Based on the electroelastic fields derived,the stress and electric displacement intensity factors,the image force acting on the dislocation are given explicitly.We find that the stress and electric displacement intensity factors depend on the effective electroelastic material constants.In the case where one of two phases is purely elastic,the stress intensity factor and image force are plotted to illustrate the influences of electromechanical coupling effect,the position of the dislocation and the material properties on the interaction mechanism.

TWO-DIMENSIONAL ELECTROELASTIC FUNDAMENTAL SOLUTIONS FOR GENERAL ANISOTROPIC PIEZOELECTRIC MEDIA

Explicit fomulas for 2-D electroelastic fundamental solutions in general anisotropic piezoelectric media subjected to a line force and a line charge are obtained by using the plane wave decomposition method and a subsequent application of the residue calculus. 'Anisotropic' means that any material symmetry restrictions are not assumed. 'Two dimensional' includes not only in-plane problems but also anti-plane problems and problems in which in-plane and anti-plane deformations couple each other. As a special case, the solutions for transversely isotropic piezoelectric media are given.

EXACT STATIC ANALYSIS OF A ROTATING PIEZOELECTRIC SPHERICAL SHELL

An exact analysis of a rotating piezoelectric spherical shell with arbitrary thickness is given. Three displacement functions are introduced to simplify the basic equations of a spherically isotropic, piezoelectric medium. By expanding the displacement functions as well as the electric potential in terms of spherical harmonics, the basic equations of equilibrium are converted to an uncoupled Euler type, second order ordinary differential equation and a coupled system of three second order ordinary differential equations. A general solution to the homogeneous equations of equilibrium is then derived. The static analysis of a rotating spherical shell is performed and the numerical example is presented. (Edited author abstract) 13 Refs.

压电发电能量储存方法的初步研究

分析了压电陶瓷正压电效应的特点,探讨了将压电陶瓷通过正压电效应产生的电能,利用镍氢电池储存的可行性,进行了初步实验研究。研究发现,通过一个低频脉冲信号激振单晶片压电振子,使压电振子弯曲变形,压电振子发出的电量能使一个15 mAh的电池在2 h内充满电,80 mAh的电池在7 h内充满电。这种利用可充电电池为储存媒介的储能方法,适用于数据处理等微电子设备,对无源条件下微型电子设备自身供能的研究开辟了新的途径。

液体媒质非接触型压电超声马达机理研究

介绍了一种液体媒质非接触型压电超声马达 ,这种马达的定子与转子是不接触的 ,且转子处于液体媒质中 ,定子压电振动所产生的能量通过定、转子间的液体传递给转子 ,从而驱动转子旋转 ,是压电超声马达的一个新的研究领域。文章给出了液体媒质非接触型压电超声马达的结构及驱动电路 ,对其运行机理进行了分析 。

压电介质二维边界积分方程中的基本解

由于压电介质的变形－电场耦合效应及压电响应的各向异性，使解析求解压电介质问题的工作变得十分复杂．若采用边界元数值方法求解，必须具备边界积分方程中的基本解．本文根据电磁场方程及连续介质力学的耦合性理论导出了二维无限域中分别在单位力及单位电荷载作用下的位移场、电势场、应力场和电位移场的解，从而确立了边界积分方程中所必需的八个基本解．

二维压电介质裂纹问题的边界积分方程解法

根据三维无限大压电体中平片裂纹的不连续电势及不连续位移边界积分方程，利用积分降维技巧，统一导出了二维压电介质中的直线裂纹（或共线裂纹群）的边界积分方程。基于这些积分方程和相应的弹性介质中裂纹的不连续位移边界积分方程的相似性，将二维压电介质中直线裂纹（或共线裂纹群）的分析问题转化成弹性介质中的裂纹问题。由弹性材料中裂纹问题的解通过参数代换即得压电弹性介质中相应问题的解。

弹性波在压电介质摩擦接触界面上的反射与透射

讨论了弹性波在压电介质摩擦接触界面上的反射和透射问题.利用Fourier分析的方法,将非线性Coulomb摩擦接触边界波动问题化为奇异积分方程问题.利用迭代-修正的方法,确定了界面上滑移和粘着区域的分布范围,同时计算了面力、相对滑移速度等参量以及由于边界非线性而引起的反射和透射的高频谐波幅值,并讨论了它们随外加力-电荷载的变化规律.

基于非局部理论的黏弹性基体上压电纳米板热-机电振动特性研究

基于非局部弹性理论研究黏弹性基体上压电纳米板的热-机电振动特性。综合考虑非局部效应、压电效应以及温度场、电场等因素影响,根据Kirchhoff板理论和Hamilton原理建立黏弹性基体上压电纳米板的热-机电振动特性分析模型,然后利用Galerkin条形传递函数方法进行求解,得到一般边界条件下压电纳米板固有频率的半解析解。通过与文献结果进行对比,验证所建分析模型与求解方法的有效性,并在此基础上系统分析非局部效应、边界条件、外电压、温度变化梯度等对压电纳米板振动特性的影响规律。结果表明,所建立的分析模型及其求解方法在分析黏弹性基体上压电纳米板的热-机电振动特性问题中准确有效。

含刚性圆柱夹杂压电介质的动力反平面特性

利用复变函数和波函数展开法对稳态SH波在含刚性可移动圆柱夹杂的无限线弹性压电介质中的散射与动应力集中问题进行研究.获得压电介质中刚性圆柱夹杂周边动应力的表达式,并对具有不同压电特征参数和不同波数情况下的夹杂边界动应力集中系数进行了数值计算.计算结果表明,边界动应力集中对外加电场压电参数具有线性依赖关系。

压电介质平面问题的基本解

应用复变函数的方法，对于压电介质平面问题，分别导出了无限介质或半无限介质受任意集中载荷作用时的复势函数基本解；这些结果可作为边界元法的基本解，以求解具有复杂边界压电体的平面问题。

二维各向异性压电介质机电耦合场的基本解

本文研究各向异性压电介质的机电耦台问题．应用平面波分解法和留数定理，首次得到了线力和线电荷作用下一般二维各向异性压电介质机电耦合场的基本解．本文的解适用于平面问题、反平面问题以及平面和反平面相互耦合问题．作为特例，文中给出了横观各向同性压电介质的基本解．

压电介质中受拉伸与弯曲联合作用的圆币形裂纹问题

以弹性位移分量和电势函数为基本未知量时，横观各向同性压电介质非轴对称三维问题的控制微分方程是四个二阶线性偏微分方程相联立的方程组。本文导出了用四个调和函数表示位移及电势的该方程组的势函数通解。作为通解的应用举例，文中求解了压电陶瓷材料中受拉伸与弯曲联合作用的圆币形裂纹问题，得到了裂纹尖端附近应力场及电位移场的解析表达式。结果表明裂尖场以及应力强度因子和电位移强度因子均表现出复杂的机－电耦合行为。