抛物线边界弹性平面受集中力时的解

1.引言在本文中,把某种点源例如集中力和脱位引起的弹性解叫做基本解。这些基本解在弹性理论中起着重要的作用。例如,利用这些基本解,边界积分方程才可以建立。在无限平面或带自由边界弹性半平面情况下,有关的基本解已经得到。最近我们提出,若一有理函数把实际区域的周界及其外部映像成单位圆及其外部,此时基本解也容     

求弹性半平面问题基本解的一个新方法

本文所提到的弹性半平面问题的基本解是一个满足特殊条件的弹性半平面的应力位移解答。这些条件为:(1)半平面内一点处作用有集中力X,Y或集中力偶M;(2)半平面边界为自由或固定边。利用平面弹性的复变函数方法,文中把弹性半平面基本解的问题归结为下列问题,使一个特定解析函数和另一个解析函数的共轭值在半平面边界上相等。对上述转化后的问题,只要利用复变函数的性质,不难从基本解的第一部分推导出基本解的第二部分。其中,基本解的第一部分是弹性全平面的本基解。从而,半平面问题基本解可以方便地得到。此外,文中还首次给出了:(1)集中力偶作用于半平面内一点时的基本解;(2)当半平面边界固定情况下的基本解。     

条带域内二维各向异性压电介质的Green函数

以压电各向异性弹性介质广义平面变形的Stroh一般解为基础,采用复变函数方法(即保角变换技术),研究了条带域介质内物理场的封闭形式解,求得了介质内某一点同时存在广义线位错和广义线力作用时的简单明确解,它就是边界元法中的Green函数.还分析了极化介质表面的电荷分布情况,并进而讨论了线电荷q与边界分布电荷间的库仑力问题.文中结果不仅适用于平面或反平面变形问题,而且也适用于两者耦合的二维变形问题.     

平面非定常热弹性问题的边界元分析

本文给出了平面非定常热弹性问题边界元解法的基本方程。采用与时间有关的基本解,建立了平面非定常热传导问题的边界积分方程。因而只须将空域离散化,减少了计算时间。     

弹性半平面问题的边界积分方程——边界元法

本文运用边界积分方程——边界元法,分析和计算具有复杂外形的孔洞承受任意分布载荷作用的弹性半平面问题。文中系统地导出了弹性半平面问题的基本解。由于采用了这一基本解,使问题大大简化。计算表明,对于那些边界线短、域范围大的问题,这种方法特别显得有效。     

含椭圆孔弹性平面基本解

运用复变函数保角变换与解析延拓方法,获得含椭圆孔无限弹性平面任意位置作用集中力的基本解,并由此获得含有限长裂纹弹性平面基本解,可作为弹性力学的典型问题.该方法较以往文献更为简捷.     

直角平面区域内固定圆形刚性夹杂问题的Green函数解

利用复变函数法、多极坐标移动技术研究了直角平面区域内含有固定圆形夹杂时的反平面问题Green函数解.首先构造出不含夹杂的完整直角平面区域内满足边界应力条件的入射位移场;其次,建立直角平面区域内固定圆形夹杂对该入射场产生的满足直角边界应力自由条件的散射波解,并由叠加原理得到介质内的总波场.最后利用夹杂边界处的位移条件确定出散射波解中的未知系数,最终得到问题的Green函数解,还通过算例讨论了夹杂边界处的径向应力和环向应力随不同波数、角度和不同夹杂位置及不同点源位置的变化情况.算例结果表明了该文方法的有效实用性.     

用拉梅-麦克斯韦尔方程解平面楔及半平面受集中力问题

借助拉梅-麦克斯韦尔方程用解析法求解半无限平面楔顶受集中力的问题. 在这一问题中的主应力坐标系和极坐标系是等价的,据此求得半无限平面楔问题的解. 把受集中力作用的半无限平面问题视为上述问题的特例, 也给出了它的解. 该求解方法直接而简单,逻辑严密.     

半元限各向同性弹性平面的周期运动载荷问题

关于半无限各向同性弹性平面的周期载荷问题,曾为路见可教授应用周期Riemann边值问题的结果所解决.本文,将应用关于半平面的Hilbert核积分公式,来求解半无限各向同性弹性平面的周期运动载荷问题.我们得到了封闭形式的解答,并且例举了实际工程中常见的一些情况加以说明. 1、基本假定与应力函数的周期性假设半无限弹性介质占有z(=x+iy)平面的下半平面S~-,以水平Ox轴作为边界,此时称它为半无限弹性平面. 下面的基本假定在本文中总是成立的:应力和位移都是以απ为周期的,应力是有界的(位移却不一定),并且所论及的边界条件都是以απ为周期的.因此,只须讨论弹     

混合边界多裂隙体在简谐变温场作用下的断裂问题（张开型）

给出了无限平面作用有简谐变化的点热源时的位移场、应力场基本解、用间接法构造出混合边值多裂隙体在简谐变温场作用下的热断裂问题的边界积分方程,并离散求解.数值结果表明,该方法求解多裂隙体的简谐热断裂问题精度好,计算工作量少.文中计算了含边界裂缝的平板、含三条平行裂缝的平板在简谐变温场作用下缝端应力强度因子的变化过程,并与实验结果进行了比较,两者吻合良好.     

PLANE STRAIN PROBLEM OF PIEZOELECTRIC SOLID WITH ELLIPTIC INCLUSION

By using the complex variables function theory, a plane strain electro-elastic analysis was performed on a transversely isotropic piezoelectric material containing an elliptic elastic inclusion, which is subjected to a uniform stress field and a uniform electric displacement loads at infinity. Based on the present finite element results and some related theoretical solutions, an acceptable conjecture was found that the stress field is constant inside the elastic inclusion. The stress field solutions in the piezoelectric matrix and the elastic inclusion were obtained in the form of complex potentials based on the impermeable electric boundary conditions.     

Effect of Maxwell stress on a moving crack with polarization saturation region in ferroelectric solid

The focus of this work is on a generalized two-dimensional problem of a crack moving in a piezoelectric solid subjected to uniform electrical load at infinity. The novel point includes that the electric field inside the crack is taken into account when polarization saturation region exists. Based on the extended Stroh formalism and complex function method, explicit expressions of both the stress fields in the solid and electric fields inside the crack are derived by using semi-permeable crack model, respectively. Effect of Maxwell stress along the crack surface is investigated and the results are illustrated graphically. It is shown that the moving speed of the crack cannot exceed the lowest bulk wave speed. It is also found that the medium properties inside the crack and surrounding the ferroelectric solid at infinity directly affect the Maxwell stress, and as a result the Maxwell stresses are remarkable and cannot be ignored under different electric load.     

Generalized 2D problem of piezoelectric media containing collinear cracks

The generalized 2D problem in piezoelectric media with collinear cracks is addressed based on Stroh's formulation and the exact electric boundary conditions on the crack faces. Exact solutions are obtained, respectively, for two special cases: one is that a piezoelectric solid withN collinear cracks is subjected to uniform loads at infinity, and the other is that a piezoelectric solid containing a single crack is subjected to a line load at an arbitrary point. It is shown when uniform loads are applied at infinity or on the crack faces that, the stress intensity factors are the same as those of isotropic materials, while the intensity factor of electric displacement is dependent on the material constants and the applied mechanical loads, but not on the applied electric loads. Moreover, it is found that the electric field inside any crack is not equal to zero, which is related to the material properties and applied mechanical-electric loads. The project supported by the National Natural Science Foundation of China (19772004)     

Saint-Venant end effects for plane deformations of linear piezoelectric solids

The recent developments in smart structures technology have stimulated renewed interest in the fundamental theory and applications of linear piezoelectricity. In this paper, we investigate the decay of Saint-Venant end effects for plane deformations of a piezoelectric semi-infinite strip. First of all, we develop the theory of plane deformations for a general anisotropic linear piezoelectric solid. Just as in the mechanical case, not all linear homogeneous anisotropic piezoelectric cylindrical solids will sustain a non-trivial state of plane deformation. The governing system of four second-order partial differential equations for the two in-plane displacements and electric potential are overdetermined in general. Sufficient conditions on the elastic and piezoelectric constants are established that do allow for a state of plane deformation. The resulting traction boundary-value problem with prescribed surface charge is an oblique derivative boundary-value problem for a coupled elliptic system of three second-order partial differential equations. The special case of a piezoelectric material transversely isotropic about the poling axis is then considered. Thus the results are valid for the hexagonal crystal class 6mm. The geometry is then specialized to be a two-dimensional semi-infinite strip and the poling axis is the axis transverse to the longitudinal direction. We consider such a strip with sides traction-free, subject to zero surface charge and self-equilibrated conditions at the end and with tractions and surface charge assumed to decay to zero as the axial variable tends to infinity. A formulation of the problem in terms of an Airy-type stress function and an induction function is adopted. The governing partial differential equations are a coupled system of a fourth and third-order equation for these two functions. On seeking solutions that exponentially decay in the axial direction one obtains an eigenvalue problem for a coupled system of fourth and second-order ordinary differential equations. This problem is the piezoelectric analog of the well-known eigenvalue problem arising in the case of an anisotropic elastic strip. It is shown that the problem can be uncoupled to an eigenvalue problem for a single sixth-order ordinary differential equation with complex eigenvalues characterized as roots of transcendental equations governing symmetric and anti-symmetric deformations and electric fields. Assuming completeness of the eigenfunctions, the rate of decay of end effects is then given by the real part of the eigenvalue with smallest positive real part. Numerical results are given for PZT-5H, PZT-5, PZT-4 and Ceramic-B. It is shown that end effects for plane deformations of these piezoceramics penetrate further into the strip than their counterparts for purely elastic isotropic materials.     

含圆孤裂纹系的压电材料反平面应变问题

应用复变函数解析延展原理，并通过求解Ｒｉｅｍａｎｎ－Ｈｉｌｂｅｒｔ问题，得到了含圆弧裂纹压电材料反平面应变问题的一般解，对单个圆弧裂纹的情形，给出了封闭形式的复函数解和场强度因子，结果表明，当无限远处或裂纹表面同时受机械载荷（应力τ＾∞或Ｔｚ）和电载荷（电位移Ｄ＾∞或电荷ｑ）联合作用时，应力强度因子仅与机械载荷有关，而电位移动强度因子仅与电载荷有关。     

The periodic cracks of an infinite anisotropic media for plane skew-symmetric loadings

This paper attempts to solve the periodic crack problems of infinitive anisotropic media for plane skew-symmetric loadings by means of the method of complex function. The problems are now reduced to the determination of two complex functions that must satisfy certain boundary conditions. In this paper, the stresses, the displacements and the boundary conditions are assumed to be periodic, and further, the stresses are assumed to be bounded at infinity. The solutions are expressed in closed forms.     

Anti-plane analysis of semi-infinite crack in piezoelectric strip

Using the complex variable function method and the technique of the conformal mapping, the fracture problem of a semi-infinite crack in a piezoelectric strip is studied under the anti-plane shear stress and the in-plane electric load. The analytic solutions of the field intensity factors and the mechanical strain energy release rate are presented under the assumption that the surface of the crack is electrically impermeable. When the height of the strip tends to infinity, the analytic solutions of an infinitely large piezoelectric solid with a semi-infinite crack are obtained. Moreover, the present results can be reduced to the well-known solutions for a purely elastic material in the absence of the electric loading. In addition, numerical examples are given to show the influences of the loaded crack length, the height of the strip, and the applied mechanical/electric loads on the mechanical strain energy release rate.     

Plane problems in piezoelectric media with elliptic inclusion

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含椭圆形刚性夹杂的压电材料平面问题

应用复变函数的Ｆａｂｅｒ级数展开方法，本文研究了含椭圆形刚性夹杂的压电材料平面问题，给出了问题的封闭解。解签表明，夹杂内的电场强度和电位移为常量。并通过算例分析，讨论了正，逆压电效应在基体孔周处的机电行为。     

Exact solution of a flat smooth punch on a piezoelectric half plane

This paper derives an exact solution for a flat smooth punch applied on a piezoelectric half plane. The piezoelectric solid occupies the lower half plane, and a flat rigid punch is applied on it. As the permittivity of the air (environment) is far less than that of the piezoelectric material, the electric induction of air may be neglected. The permittivity of the punch is also far less than that of the piezoelectric material and consequently the normal component of the electric displacement vanishes at the contact boundary. The exact solution is obtained by eigen-function representation and analytic continuation. The distribution of pressure under the punch has been found. The electric field along the surface of the lower half plane is extracted in a closed form.