初应力下压电半导体板中SH波的传播特性

针对无限大n-型压电半导体板,论文理论研究了其在初应力作用下水平剪切波的传播特性。基于压电半导体三维宏观理论和边界条件得到色散关系,结合数值算例,系统分析了边界条件、初始载流子浓度、板的厚度和初应力大小对SH波传播特性的影响。此外,讨论了初应力下两种不同材料中的SH波传播。研究显示：较小的初应力对相速度影响很小可忽略,当初应力达到一定值时波速急剧下降;类似地,初应力足够大时衰减才会逐渐加强。计算结果对压电半导体器件设计具有一定的理论指导意义。     

ACOUSTIC REFLECTION FROM A PERIODIC ELASTIC／PIEZOELECTRIC PLATE

The acoustic reflected pressure from a periodic elastic/piezoelectric laminated plate is studied for the purpose of acoustic reflection control. A finite difference/boundary integral procedure to determine the reflected pressure from the fluid-loaded plate is described. In the numerical model, a Green‘s function in the form of infinite sum is employed and a boundary integral is performed to replace the fluid pressure at fluid/solid interface by a continuum of point sources weighted by the normal acceleration of the elastic plate. The equation system is then solved only in the solid domain. It is demonstrated that an appropriate applied voltage potential across the piezoelectric layer has the effect of cancelling the fundamental propagating mode, and there is no reflection for frequencies up to the cut-off frequency of the next propagating mode if the fundamental mode has been eliminated.     

压电层合板结构振动控制的有限元法

利用有限元方法模拟压电结构的振动控制，从Ｈａｍｉｌｔｏｎ理论出发推导出具有压电传感器及激励器的层合板的电耦合动力方程，应用Ｌｙａｐｕｎｏｖ及负速度反馈控制算来实现振动的控制。     

粘性流体中弹性板振动的有限元耦合问题

流体－结构耦合作用问题是工程中比较常见的问题，具有重要意义，由于流体计算的复杂性，迄今为止，大部分的流体－结构耦合分析都是建立在对流体充分简化的基础上，尤其是将流体视为无粘、无旋的理想流体。该文在近年来前人工作的基础上，发展了一种流体－弹性结构耦合计算模式。流体视为不可压、有粘的介质，流场没有自由表面。该文采用ＳＵ／ＰＧ方法形成流体的有限元方程，采用ＡＬＥ格式处理流体和结构之间的移动界面。采用预估     

覆盖层与基底极化方向相反时压电层状半空间中的B-G波

对于覆盖层与基底介质极化方向相反的压电层状半空间,在自由表面电学开路和短路两种情况下,分别用解析的方法得到了Bleustein-Gulyaev波传播的相速度方程或相速度的表达式 ;以工程技术中应用的压电材料为例考察了波速随覆盖层厚度h的变化规律.为了分析表面金属薄膜对波的传播速度的影响,计算了机电耦合系数k2与h的关系,结果表明 :层状结构B-G波传播时具有很小的穿透深度,同时在h取适当值时依然可使k2保持相当高的值.     

具有压电材料弹性环形板的屈曲

对在不同位置粘有任意多对压电片的弹性环形板在电压和径向压力作用下的轴对称屈曲进行了研究．根据压电效应的等效作用量，初参数法以及传递矩阵方法得到了环板屈曲的特征方程．对不同位置及不同宽度的压电片，计算了结构的屈曲载荷．并得到了稳定性边界曲线．     

ANALYSIS OF THE DYNAMIC BEHAVIOR OF A GRIFFITH PERMEABLE CRACK IN PIEZOELECTRIC MATERIALS WITH THE NON-LOCAL THEORY

The dynamic behavior ofa Griffith permeable crack under harmonic anti-plane shearwaves in the piezoelectric materials is investigated by use of the non-local theory.To overcome themathematical difficulties,a one-dimensional non-local kernel is used instead of a two-dimensionalone for the anti-plane dynamic problem to obtain the stress and the electric displacement near thecrack tips.By means of Fourier transform,the problem can be solved with a pair of dual integralequations that the unknown variable is the jump of the displacement across the crack surfaces.These equations are solved with the Schmidt method and numerical examples are provided.Con-trary to the previous results,it is found that no stress and electric displacement singularities arepresent at the crack tip.The finite hoop stress and the electric displacement depend on the cracklength,the lattice parameter of the materials and the circle frequency of the incident waves.Thisenables us to employ the maximum stress hypothesis to deal with fracture problems in a naturalway.     

有限厚度砂床对波浪载荷的响应

本文采用水-土两相介质混合物的连续介质力学理论分析了有限厚度砂床对波浪载荷的响应。土床看作饱和孔隙弹性介质,用Biot理论来描述流动和变形的耦合效应,波浪用线性水波描述。在上述假设下得到了描述土床对波浪载荷响应的基本方程。用解沂-数值方法给出了土床中位移、应力和孔隙水压力的分布并将理沦计算结果与波浪-砂床模型试验的实验资料进行了比较。文章还对影响土床对波浪响应的参量特性进行了分析和讨论。根据参量研究、理论计算与实验资料比较的结果,可以得出结论:本文所提供的理论模型和计算方法能用来估算海床对波浪载荷的影响。     

SOLUTION OF MULTIPLE CRACKS IN A FINITE PLATE OF AN ELASTIC ISOTROPIC MATERIAL WITH THE DISTRIBUTED DISLOCATION METHOD

This paper presents a numerical solution to model multiple cracks in a finite plate of an elastic isotropic material. Both the boundaries and the cracks are modeled by distributed dislocations. This method results in a system of singular integral equations with Cauchy kernels which can be solved by Gauss-Chebyshev quadrature method. Four examples are provided to assess the capability of this method.     

含椭圆孔有限大薄板弯曲应力分析

利用各向异性体弹性平面理论中的复势方法,以Faber级数为工具,对含椭圆孔有限大各向异性板弯曲问题进行应力分析,得出有限大含椭圆孔各向异性板弯曲的级数解形式,分析了有限大含椭圆孔板在受到弯曲载荷时孔边的应力分布,并讨论了各种参数对应力分布的影响,给出了有益的结论.     

ANALYSIS AND EXPERIMENT ON TRANSIENT DYNAMIC RESPONSE IN FINITE MINDLIN PLATE

The transient wave propagation in the finite rectangular Mindlin plate is investigated by the analytical and experimental methods. The generalized ray method (GRM) which has been successfully applied to study the transient responses of beams, planar trusses, space frames and infinite layered media is extended to investigate the transient wave propagation and early short time transient response in finite Mindlin plate. Combining the wave solution, the shock source and the boundary conditions, the ray groups transmitted in the finite rectangular plate can be determined. Numerical simulations and experiments are performed and compared with each other. The results show that the transient wave propagation and early short time transient responses in the finite plate can be studied using the GRM. The early short time transient accelerations are very large for the finite plate subjected to the unit impulse, while the early short time transient displacements are very small. The early short time transient accelerations under the unit impulse are much larger than those under the unit step impulse. The thickness and material characteristics have remarkable effects on the early short time transient responses.