正交各向异性弹性层/压磁半空间结构中Love波的传播

分析了正交各向异性弹性层/压磁半空间结构中Love波的传播特性,得到了Love波传播时的解析解,基于推导的频散方程,数值分析了正交各向异性层的切割角度对Love波频散关系的影响,结果显示相速度对切割角度有很大的依赖性。     

非理想界面功能梯度压电/压磁层状半空间结构中的SH波

研究非理想界面下功能梯度压电/压磁层状半空间结构中SH波的传播特性。界面性能由“弹簧”模型表征, 假设功能梯度压电层材料性能沿层厚度方向指数变化, 其表面为电学开路。推导了频散方程, 并结合数值算例分析了界面性能、功能梯度压电层的梯度变化和厚度对相速度的影响。研究结果对功能梯度压电/压磁复合材料在声波器件中的应用提供了理论依据。     

饱和土层中Love波的传播特性

基于Ｂｉｏｔ的液体饱和孔隙介质模型，考虑孔隙流体粘性，导出了弹性半空间上饱和土层中Ｌｏｖｅ波的复频散方程，然后将其转化为两个实方程并利用迭代的方法进行求解。讨论了Ｌｏｖｅ波的波速范围、Ｌｏｖｅ波的频散和衰减特性以及Ｌｏｖｅ波的位移分布。     

非理想界面功能梯度压电/压磁双材料中的SH界面波

研究了非理想界面功能梯度压电/压磁双材料中SH界面波的传播特性,这里假定上、下半空间材料性能在垂直于界面的方向是按指数函数变化的。界面的机械条件由"弹簧"模型表征,即应力是连续的而位移是间断的;界面电磁学条件考虑电位移、电势、磁感、磁势连续和电学短路、磁学开路两种情况。推导了界面波显函形式的频散方程,通过数值计算表明了材料组合形式、界面非理想程度以及材料梯度变化对界面波相速度的影响。     

正交各向异性空心圆柱体的周向SH波

基于线性三维弹性理论,得到了正交各向异性管道中位移表示的周向波控制方程.波动方程中的轴向位移独立于其它两个方向.即波的传播可以分解为SH波和类Lamb波.通过贝塞尔函数求得了这个周向SH波频散方程.方程中决定周向SH波特性的弹性常数有两个,一个决定了波的频率,另一个决定了波速.最后分别讨论了两个弹性常数和波数变化对周向SH波位移模式的影响.     

间隙波在功能梯度压电板和压电半空间结构中的传播

研究了间隙波在功能梯度压电板和压电半空间结构中的传播性质.功能梯度压电板的材料性能沿x2方向呈指数变化,首先推导了间隙波传播时的解析解,利用界面条件得到了间隙波的频散方程,基于推导的频散方程,结合数值算例分析了功能梯度压电材料的梯度、压电层厚度以及材料性能对间隙波相速度的影响,研究结果对功能梯度压电材料的覆层结构在声波器件中的应用具有重要的参考价值.     

粘弹正交各向异性空心圆柱体周向SH波

基于Kelvin-Voight模型,推导了粘弹正交各向异性空心圆柱体周向SH波控制方程,得出了SH波特性受两个弹性常数与粘性系数的影响。通过第一类和第二类Bessel函数,求出频散方程。计算了四种不同径厚比下的相速度频散曲线和衰减曲线,分析了径厚比的变化对频散和衰减曲线的影响。为了与正交各向异性相比较,计算了粘弹各向同性空心圆柱体中周向SH波,并讨论了两个弹性常数和粘性系数对频散曲线和衰减曲线的影响。     

含泥沙的流固层状介质界面波传播特性研究

在弹性波传播理论的基础上,结合边界条件,导出了流固层状介质导波特征方程,计算特征方程的频散曲线;然后结合Urick、Urick-Ament和Harker-Temple这三种悬浊液模型,计算流体层中的泥沙含量和颗粒粒径与界面波波速的关系;分析比较不同模型下泥沙含量及颗粒粒径与波速的关系图,讨论不同参数对波速的影响,得出了三种模型下波速随泥沙含量和颗粒粒径的变化趋势,最后发现Urick-Ament模型同时适用于检测悬浊液的泥沙含量和泥沙颗粒粒径,且在三种模型中有相对较好的可靠性和实用性。     

有对称液层负载时各向异性板中Lamb波的传播

1　引　言　　 L amb波是固体薄板中传播的一种弹性波 ,最初有关 Lamb波的微传感的理论研究大都只局限在各向同性板材中 ,由于在各向异性压电板上可以高效激发 L amb波 ,灵敏度高 ,体积小 ,性价比高等特点 ,因而各向异性材料有更大的实用性 ,实验上已有各向异性压电板传感器的尝试 [1] ,特别是在生物传感领域 ,由于能检测到病毒等 ,因而特别具有吸引力。在理论上 S.G.Joshi[2 ] ,Chimenti[3 ] ,Vinay Day-al[4 ] 都对各向异性板中的 L amb波进行了理论推导和数值计算 ,为了对各向异性材料微传感性的机理有进一步深入了解 ,本文研究若干…     

非饱和地基中Love波的传播特性

基于非饱和多孔介质的波动方程,考虑了土中水,气体与土骨架之间的粘性耦合作用,建立了弹性半空间上非饱和土层中Love波的弥散方程。首先分析了饱和度与频率对非饱和孔隙介质中剪切波速的影响。然后运用数值方法得到了不同饱和度下土层中多种Love模态波的弥散特性和位移分布情况,并用图表的形式给出。数值计算结果表明,上覆非饱和土层中Love波的传播速度和衰减系数不仅具有频散性,而且与土层的饱和度有关。在不同饱和度时的高模态(n≥2)的Love波的截止频率值不同。此外,讨论了饱和度对Love波水平位移幅值的影响。     

功能梯度压电层/压电半空间结构中Love波的传播:一种改进的拉盖尔多项式方法

使用传统的拉盖尔多项式方法求解层状半空间结构时,存在因层间材料差异所造成的应力、电位移不连续的现象。为了克服此方法的不足,提出了一种改进的拉盖尔多项式方法,研究了功能梯度压电层状半空间中Love波的传播特性。与文献中应用WKB法得到的结果进行对比,验证了该方法的正确性。计算和分析了相应的频散曲线、应力和电位移分布曲线。结果表明:该方法能够避免因层间材料差异所造成的应力、电位移不连续现象的出现;高频Love波的应力和电位移主要分布在功能梯度压电层中速度较低的一侧。该研究为基于Love波传感器的设计与优化奠定了一定的理论基础。     

Antiplane piezoelectric surface waves over a ceramic half-space with an imperfectly bonded layer

We study surface wave propagation over a piezoelectric half-space with an imperfectly bonded mass layer. The imperfect interface between the half-space and the layer is described by the so-called shear-lag model with an elastic constant characterizing the interface physical property. An analytical solution is obtained. Discussion and numerical solutions are presented.     

Propagation of thickness-twist waves in an inhomogeneous piezoelectric plate with an imperfectly bonded interface

The propagation of thickness-twist waves in an inhomogeneous piezoelectric plate with an imperfectly bonded interface is investigated. Based on the spring-type relation, the imperfectly bonded interface is dealt with, and the exact solution is obtained from the equations of the linear theory of piezoelectricity. The amplitude ratio between the incident wave and the reflected wave, the displacement component and the stress component are all obtained and plotted. Both theoretical analysis and numerical examples show that the effect of the mechanical imperfection on the wave propagation is more evident than that of the electrical imperfection. When the incident wave frequency and the mechanical imperfect parameter meet some particular relation, no reflected waves can appear in the piezoelectric plate. The results are of fundamental importance to the design of resonators and other devices when imperfect joints are considered.     

Multiple cracks on the interface between a piezoelectric layer and an orthotropic substrate

In the present work, we investigate the problem of multiple cracks on the interface between a piezoelectric layer and an orthotropic substrate. The method of dislocation simulation and singular integral equation are used to solve the crack problem. The theoretical derivation is verified by the classical result in a special case. Numerical results of the stress intensity factor are obtained, and thereby the effects of geometrical parameters and material orthotropy are surveyed. The optimal stiffness ratio of the orthotropic substrate is suggested for the purpose of interfacial fracture prevention, which is significant for the design and assessment of such a kind of smart structures.     

Interfacial waves in dissimilar piezoelectric cubic crystals with an imperfect bonding

This paper studies propagation of shear waves along a weak interface of two dissimilar piezoelectric cubic crystals. Two piezoelectric cubic crystals are bonded along a specified cut direction. For an imperfect electrode interface, a dispersion relation of interfacial waves is derived explicitly. Numerical solutions are evaluated for several commonly-used piezoelectric cubic crystals. Our results show that interfacial imperfection alters the velocity of the interfacial shear waves. In particular, sometimes the interfacial shear waves may not exist for a perfect grounded interface and exist only for an imperfect electrode interface.     

Love waves on a half-space with a gradient piezoelectric layer by the geometric integration method

The propagation of Love waves on an elastic homogeneous half-space with a piezoelectric gradient covering layer is studied by the geometric integration method in this article. First, the state transfer equation of a Love wave is derived from the governing equations and constitutive relations. Then, the transfer matrix of the state vector is obtained by solving the state transfer equation of a Love wave and then the stiffness matrix is obtained. By combining transfer matrices and the stiffness matrices of the gradient covering layer and the homogeneous half-space, the total surface stiffness matrix of a Love wave is obtained. Lastly, the application of the electrically open circuit and short circuit conditions and mechanically traction-free conditions gives the frequency dispersive relation of a Love wave. For the gradient covering layer, the material constants at the bottom of the covering layer may be greater or smaller than that at the top of the covering layer. The two situations and three kinds of gradient profiles for each of these two situations are investigated. The numerical results show that the Love wave speed is sensitive to not only the material constants at the bottom and the top of the covering layer, but also the gradient profiles of the covering layer.     

Propagation and amplification of gap waves between a piezoelectric half-space and a semiconductor film

Summary. We study wave propagation in a piezoelectric ceramic half-space with a thin semiconductor film and an air gap between the film and the half-space. Two-dimensional equations for a thin film are used to model the semiconductor film and the air gap. The half-space is governed by the three-dimensional equations of linear piezoelectricity. It is shown that an anti-plane wave can propagate in such a system. An equation that determines the dispersion relation of the wave is obtained. Solutions to the equation show that the wave has both dispersion and attenuation, and can be amplified by a biasing dc electric field.     

含不完美界面的磁电复合材料倾斜裂纹问题

研究了含非完美界面的双层压电/压磁复合材料中压电相存在一个倾斜于界面的Ⅲ型裂纹问题。采用弹簧型耦合界面模型模拟非完美界面,运用Fourier积分变换法将裂纹面条件转化为奇异积分方程,并使用Lobatto-Chebyshev方法数值求解了裂纹尖端应力强度因子（SIF）。详细地研究了裂纹尖端SIF与界面参数、压电/压磁材料参数和材料的层厚、裂纹的倾斜角、裂纹与界面的距离等几何参数的关系。结果表明：力学不完美性可以独立地增大SIF,而磁学、电学不完美性只有与力学不完美性耦合时才会减小SIF;力学-电学、力学-磁学不完美性的耦合会减小SIF,而磁学-电学不完美性的耦合不会影响SIF;磁场作用下,增大压磁层弹性模量会减小SIF,而增大压电层压电系数,减小压电层弹性模量和介电常数,均会减小SIF;界面不完美性会影响SIF随裂纹倾斜角度或裂纹与界面之间距离的变化规律;在一定范围内增加压电层或压磁层厚度可以减小SIF。     

A piezoelectric screw dislocation in a three-phase composite cylinder model with an imperfect interface

The electroelastic coupling interaction between a piezoelectric screw dislocation and the embedded circular cross-section inclusions with imperfect interfaces in piezoelectric solids is investigated by using a three-phase composite cylinder model. By means of a complex variable technique, the explicit solutions of electroelastic fields are obtained. With the aid of the Peach-Koehler formula, the explicit expression for the image force exerted on the piezoelectric screw dislocation is derived. The image force on the dislocation and its equilibrium positions near one of the inclusions are discussed for variable parameters (interface imperfection and material electroelastic dissimilarity) and the influence of nearby inclusions is also considered. The results show that when compared with the previous solution (the perfect interface), more equilibrium positions of the screw dislocation in the matrix may be available due to the effect of the interface imperfection when the dislocation is close to the electroelastic stiff inclusion. It is also found that the magnitude of the image force exerted on the piezoelectric screw dislocation produced by multiply inclusions is always smaller than that produced by a single inclusion and the impact of nearby inclusions on the mobility of the screw dislocation is very important.     

Propagation of Love waves in an elastic layer with void pores

The paper presents a study of propagation of Love waves in a poroelastic layer resting over a poro-elastic half-space. Pores contain nothing of mechanical or energetic significance. The study reveals that such a medium transmits two types of love waves. The first front depends upon the modulus of rigidity of the elastic matrix of the medium and is the same as the love wave in an elastic layer over an elastic half-space. The second front depends upon the change in volume fraction of the pores. As the first front is well-known, the second front has been investigated numerically for different values of void parameters. It is observed that the second front is many times faster than the shear wave in the void medium due to change in volume fraction of the pores and is significant