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 共查询到19条相似文献,搜索用时 78 毫秒
1.
舒小平 《功能材料》2007,38(A09):3647-3649
针对梯度功能压电复合材料球壳热弹性响应提出了简单而精确的近似解。借鉴纤维复合材料层合结构的研究方法,将梯度功能压电复合材料球壳沿径向分为若干层,各层视为均匀材料,从而导出力-电-温度多场耦合近似解。只要层数足够大,解将收敛于精确解。该方法的另一个优点在于解的方法对材料性能的变化方式(函数)没有要求,具有普适性。这对其它非均匀材料结构的分析具有推广、应用价值。  相似文献   

2.
朱炳麒  卓家寿  周建方 《工程力学》2006,23(12):63-67,72
用弹性力学直角坐标辛体系中类似的形式,定义了极坐标问题径向和环向辛体系的Hamilton函数,对其守恒性进行了研究,由Hamilton对偶方程推出了Hamilton函数的守恒律,同时给出了守恒条件,指出两种极坐标辛体系中Hamilton函数是否守恒均取决于两侧边的荷载和位移情况。在径向和环向辛体系中都给出了算例,验证了Hamilton函数的守恒律。这一守恒律丰富了弹性力学辛体系的理论内容,不仅对于弹性力学极坐标问题的理论分析有所帮助,也为极坐标问题的数值计算分析提供了一个判断依据。  相似文献   

3.
压电元件驱动的功能梯度弹性薄板的屈曲   总被引:4,自引:0,他引:4  
丁丽霞  刘玮 《功能材料》2006,37(8):1229-1231,1238
考虑功能梯度薄板,其上下表面嵌有压电执行元件.根据逆压电效应将电压转换成作用于板上的等效电载荷.假设梯度材料的弹性参数为板厚度方向坐标的幂函数,基于经典板理论,导出了功能梯度弹性薄板小挠度屈曲平衡微分方程.利用双三角级数展开法,得到了四边简支具有压电元件的功能梯度矩形板的临界屈曲载荷,在此基础上通过数值例子讨论了弹性板的几何尺寸、材料梯度指数的变化对临界电压(载荷)的影响.研究结果表明,材料的梯度指数对临界电压有重要影响,并且通过调整作用于执行元件上的电压的大小和方向,可实现对结构稳定性的有效控制.  相似文献   

4.
刘玮  闫铂 《振动与冲击》2007,26(5):1-3,7
考虑一功能梯度薄板,其上下表面嵌有压电执行元件。根据逆压电效应,将电场强度转换成作用于板上的等效电载荷。假设梯度材料的物性参数为板厚度方向坐标的幂函数,应用达朗贝尔原理,导出了具有压电元件的功能梯度弹性薄板的动力学方程。采用变量分离与Navier解,得到四边简支功能梯度板的固有特性与电场强度间的关系。并进一步通过数值例子讨论了电场强度、材料的梯度指数等对板固有特性的影响。研究结果表明,调整作用于执行元件上的电场强度可以实现对板的振动特性的控制,而材料的梯度化可影响板的固有频率,在设计中应予以考虑。  相似文献   

5.
梯度功能材料的研究   总被引:17,自引:3,他引:17  
梯度功能材料是五年前由日本科学家提出的新概念和新思想,其两侧由不同性能的材料组成,以对付苛刻的使用环境;而中间部分的组成和结构又是连续变化的,使其内部界面消失,以减小和克服结合部位的性能不匹配因素。这类材料在航天事业和核工业中有看广阔的应用前景和极高的使用价值。本文着重介绍了梯度功能材料的设计思想、目前的研究现状、以及我们在这方面做的一些工作。并综述和比较了各类制备工艺技术。  相似文献   

6.
基于Hamilton体系的弹性行进索精确模态分析   总被引:1,自引:0,他引:1  
用Hamilton体系动力学建立弹性轴向行进索动力学微分方程.引入位移的对偶函数,根据给定的边界条件,导出Hamilton对偶方程组.用分离变量法求解系统的各阶共轭特征值对和特征函数对,并提出特征函数的辛共轭正交归一关系.考虑前若干阶线性振动模态,使用展开定理,将索的位移表示成共轭的模态函数的级数和.算例分析了索的模态和构形响应随不同行进速度的变化,得到索的响应构形图.  相似文献   

7.
梯度功能材料的研究与展望   总被引:25,自引:0,他引:25  
梯度功能材料是基于一种全新的材料设计概念合成的新型复合材料,本文叙述了梯度功能材料的概念和开发背景,着重介绍了梯度功能材料的研究内容和现状以及在航天、核能、电子、光学、生物医学等领域的应用前景,并展望了这种新材料今后的研究动向。  相似文献   

8.
为分析多物理场下含双参数弹性基础压电功能梯度圆柱壳的自由振动特性,以含Pasternak-Winkler 弹性基础压电功能梯度圆柱壳为对象,采用1 阶剪切变形理论和Hamilton 变分原理推导多场作用下含弹性基础压电功能梯度圆柱壳的模态频率方程,讨论弹性基础参数、温度梯度、压电层的材料种类和功能梯度层的材料组分等对模态频率的影响。结果表明,模态频率随温度梯度的增大而减小,随陶瓷体积分数指数和弹性基础参数的增大而增大;选用BaTiO3时,圆柱壳的模态频率以及对温度梯度的敏感性均最大,而受外激励电压的影响最小;相较于外激励电压,温度梯度对模态频率影响较大。  相似文献   

9.
梯度功能材料热弹性力学问题计算方法的研究   总被引:10,自引:2,他引:8  
苗秀芝  张幸红 《功能材料》1999,30(2):122-125
介绍了有关梯度功能材料热弹性力学问题的最新研究方法,评述了所采用的研究方法和特点。  相似文献   

10.
梯度功能材料热弹性应力的研究进展   总被引:1,自引:0,他引:1  
介绍了近年来国外有关梯度功能材料热弹性应力问题的最新研究进展,评述了所采用的研究方法的特点。  相似文献   

11.
马力  吴林志  聂武 《工程力学》2006,23(1):47-51
利用Fourier变换技术将混合边值问题化为对偶积分方程,求解对偶积分方程得到应力强度因子以及电位移强度因子的表达式。最后通过数值计算讨论了材料参数、载荷条件以及裂纹的几何参数等对功能梯度压电材料中裂纹尖端应力强度因子的影响。  相似文献   

12.
Composite materials fail under extreme working conditions, particularly at high temperature, due to delamination (separation of fibers from matrix). And therefore it is needed to switch over functionally graded materials (FGMs) which can sustain at high temperature conditions (250–2000°C). There is a need to analyze the fracture and fatigue characteristics of FGM structures and so through this review the emphasis is given on fracture analysis of FGM materials. It has been reported that a combination of extended finite element method and isogeometric analysis methodologies has been used for general mixed-mode crack propagation problems after the introduction of extended isogeometric analysis. Furthermore, recent computational advances have been in the form of multiscale simulations where the part of model is simulated by a finer modeling scale, which can represent details of the material behavior and the interacting effects of material constituents in the finest way. The review is also focused on new advances in analytical and numerical methods for the stress, vibration, and buckling analyses of FGMs. Emphasis has been primarily on to restrict 2D analysis with sorts of compromise in the accuracy of results. First shear deformation theory (FSDT) and third-order shear deformation theory have been extensively used among the various 2D plate theories. FSDT can help us in terms of getting reasonably accurate results with less computational afford. This paper also outlines review on carbon nanotubes (CNT) reinforced FGMs, functionally graded nanocomposites, functionally graded single-walled CNT, FG nanobeam as well as functionally graded piezoelectric materials. Future applications would be based on these smart materials which are supposed to serve us in adverse conditions. Of course, with rise and advent of promising nanotechnology and its potential impact on aerospace industry as well as on other areas, it becomes important to us to compile this review article.  相似文献   

13.
A graded finite element method code based on Rayleigh–Ritz energy formulation is developed and implemented to study the elastic behavior of a layered plate loaded by a solid isotropic cylinder and a functionally graded interlayer. The applied nonaxisymmetric loading to the inner cylinder induces a stress concentration in the flexible part of the joint. The effects of different thicknesses and power law exponents of functionally graded interlayer on the distribution of displacements and stresses are investigated, which verifies the ability of functionally graded material to control the stress and displacement waves. The time-dependent response of the structure is also obtained based on Newmark's time integration method.  相似文献   

14.
Using a similar procedure to the Hamiltonian system based model [Wang, J.S., Qin, Q.H., 2007. A symplectic model for piezoelectric wedges and its application to analysis of electroelastic singularities, Philosophical Magazine 87 (2), 225–251], the mixed-variable state space formulation is developed for functionally graded piezoelectric material (FGPM) strips and laminates, in which the material inhomogeneity is considered. For dissimilar homogeneous piezoelectric laminates, the state space formulation degenerated to a Hamiltonian system. Applying the developed model, we analyzed the decay of Saint-Venant end effects in a single FGPM strip and a FGPM laminate. The numerical results show that the decay rate depended strongly on the eigenvalue of the proposed operator matrix for the single FGPM strip. By using the coordinate transformation technique and the continuity conditions on the interface between two dissimilar materials (different piezoelectric properties or different material inhomogeneous parameters), the decay rates are also determined for multi-layered FGPM laminates, including dissimilar piezoelectric laminates (without material inhomogeneity) as a special case. Numerical results are presented to show the applicability of the proposed state space model to piezoelectric and FGPM laminates. In addition, the variation of the decay rate with the thickness has also been investigated for the dissimilar homogeneous piezoelectric laminates. This study indicates that material inhomogeneity plays an important role in Saint-Venant end effects for FGPM laminates, as in the case of a single FGPM strip [Borrelli, A., Horgan, C.O., Patria, M.C., 2004. Exponential decay of end effects in anti-plane shear for functionally graded piezoelectric materials. Proceedings of the Royal Society of London Series A 460, 1193–1212].  相似文献   

15.
薛雁  聂辉  冯文杰 《工程力学》2008,25(4):70-74
该文考察了磁电弹性功能梯度板的反平面问题。该板具有多个垂直于边界的共线裂纹。裂纹表面采用磁电不穿透或可穿透假设。应用积分变换和位错密度函数将问题化为柯西奇异积分方程求解。导出和分析了场强度因子和能量释放率。数值结果表明了载荷组合参数、材料梯度指数及裂纹构形对裂尖断裂行为的影响。  相似文献   

16.
为了获得高的热电能量转换效率,可以把不同单体联接制成多段热电装置形成梯度结构(FGM),能有效扩大工作温度区间;同时又可以使每段材料工作在其最佳温度范围内,获得最佳的热电优值,有效提高热电转换效率.概述了梯度结构热电材料的设计与研究现状,并简要介绍了梯度结构中的界面稳定性和性能表征.  相似文献   

17.
Buckling analysis of perfect circular functionally graded plates with surface-bounded piezoelectric layers based on the first-order shear deformation theory is presented in this article. The material properties of the functionally graded (FG) layer are assumed to vary continuously through the plate thickness by distribution of power law of the volume fraction of the constituents. The plate is assumed to be under constant electrical field and two types of thermal loadings, namely, the uniform temperature rise and nonlinear temperature gradient through the thickness. Also, the stability of a plate under radial mechanical compressive force is examined. The equilibrium and stability equations are derived based on the first-order shear deformation plate theory using a variational approach. The boundary condition of the plate as an immovable type of the clamped edge is considered. Resulting equations are employed to obtain the closed-form solution for the critical buckling temperature for each loading case. The effects of electric field, piezo-to-host thickness ratio, and power law index of functionally graded plates subjected to thermo-mechanical-electrical loads are investigated. The results are compared with the classical plate theory and verified with the available data in the open literature.  相似文献   

18.
针对任意材料梯度分布形式的四边简支、接地功能梯度压电材料平板,把Haar小波方法引入平板结构的三维分析中。由于小波方法在求解存在局部奇异性问题上的优越性,对于任意材料梯度变化,甚至材料性质存在局部剧烈变化的情况,各分量的Haar小波级数解都有较好的收敛性。通过算例,该文分析了在机械荷载、电荷载分别作用下,材料不同梯度形式、平板上下表面材料性质差异对功能梯度压电平板结构响应的影响。  相似文献   

19.
Micro‐tools offer significant promise in a wide range of applications such as cell manipulation, micro‐surgery, and micro/nanotechnology processes. Such special micro‐tools consist of multi‐flexible structures actuated by two or more piezoceramic devices that must generate output displacements and forces at different specified points of the domain and at different directions. The micro‐tool structure acts as a mechanical transformer by amplifying and changing the direction of the piezoceramics output displacements. The design of these micro‐tools involves minimization of the coupling among movements generated by various piezoceramics. To obtain enhanced micro‐tool performance, the concept of multifunctional and functionally graded materials is extended by tailoring elastic and piezoelectric properties of the piezoceramics while simultaneously optimizing the multi‐flexible structural configuration using multiphysics topology optimization. The design process considers the influence of piezoceramic property gradation and also its polarization sign. The method is implemented considering continuum material distribution with special interpolation of fictitious densities in the design domain. As examples, designs of a single piezoactuator, an XY nano‐positioner actuated by two graded piezoceramics, and a micro‐gripper actuated by three graded piezoceramics are considered. The results show that material gradation plays an important role to improve actuator performance, which may also lead to optimal displacements and coupling ratios with reduced amount of piezoelectric material. The present examples are limited to two‐dimensional models because many of the applications for such micro‐tools are planar devices. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

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