共查询到20条相似文献,搜索用时 421 毫秒
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力学中许多问题如弹塑性问题,弹塑性接触问题、塑性耦合问题,渗流问题等,其约束条件或者边界形态是无法预知的,只能用一组不等式表示,属于非线性问题,经典的变人原理在求解此类问题时只能采取繁琐的迭代过程。 相似文献
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关于平面问题分类的再探讨张雷顺(郑州工学院,郑州450002)由于平面问题比较简单,所以在弹性力学教材中,对平面问题给出了较多的篇幅,也列举了较多的例题.在工程中,相当多的问题也都近似为平面问题处理.但在认定平面问题和进行平面问题分类方面,作者发现时... 相似文献
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关于平面问题分类的再探讨张雷顺(郑州工学院,郑州450002)由于平面问题比较简单,所以在弹性力学教材中,对平面问题给出了较多的篇幅,也列举了较多的例题.在工程中,相当多的问题也都近似为平面问题处理.但在认定平面问题和进行平面问题分类方面,作者发现时... 相似文献
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动态设计变量优化方法及其在工程静力学通用程序设计中的应用 总被引:5,自引:0,他引:5
本文提出动态设计变量优化新方法并解决理论和工程问题,该方法首先构建目标函数框架,然后根据具体问题的输入条件,动态地进行设计变量分配和合理排序,形成实际问题的动态目标函数。基于动态设计变量优化方法,编制出一个能解决单刚体、刚体系的平面和空间问题、摩擦问题和桁架所有工程静力学平衡问题的通用程序,并通过实例分析验证。为解决更多工程领域问题提供有效新观点。 相似文献
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由于变厚度板弯曲问题的控制分方程复杂,直接求解其基本解推导边界积分方程建立边界元分析法较为困难,本文通过引入等效荷载,等效刚度,将此问题的控制微分方程化成与普通薄板弯曲问题基本方程相同的形式,利用求解通板弯曲问题的边界元迭代求解,建立了分析变厚度板弯曲问题的蛤法,算例表明本方法理正确,精度良好。 相似文献
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一维杆与结构接触冲击问题的计算黄剑敏,任文敏(清华大学工程力学系,北京100084)1引言工程中大量存在着杆与结构的接触冲击问题,对这类问题的研究极为重要,但这方面的论著甚少,理论所能解决的问题更少,仅在极个别的情况下有精确解。T.T.R.Hughe... 相似文献
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求解线性方程组的一种新方法 总被引:7,自引:1,他引:7
将线性方程组的一般系数矩阵转化为对称正定矩阵,从而把原线性方程组的求解问题转化为一个等价变分问题的极少值点寻优问题,借助对分寻优法进行求解。算例结果表明,本文方法不仅对于良态线性方程组的求解问题是有效的,而且对于病态线性方程组的求解问题同样是有效的。 相似文献
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一维杆与结构接触冲击问题的计算黄剑敏,任文敏(清华大学工程力学系,北京100084)1引言工程中大量存在着杆与结构的接触冲击问题,对这类问题的研究极为重要,但这方面的论著甚少,理论所能解决的问题更少,仅在极个别的情况下有精确解。T.T.R.Hughe... 相似文献
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引入分数因子和分数增量,给出了分数阶微积分的定义和性质;基于分数阶导数的定义,证明了含有分数因子的等时变分与分数阶算子的交换关系;提出了分数阶完整保守和非保守系统的Hamilton原理;建立了分数阶完整保守系统和非保守系统的运动微分方程;得到了分数阶完整保守系统的循环积分;并利用分数阶循环积分导出分数阶罗兹方程.最后给出了两个例子.研究表明利用分数因子给出的分数阶微分方程是一个含有分数因子的通常的微分方程,那么分数阶系统运动微分方程的求解都可以采用通常微分方程的求解方法. 相似文献
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薛大为 《应用数学和力学(英文版)》1991,12(3):227-236
Two generalized variational principles on nonlinear theory of elasticity with finitedisplacements in which the σ_(ij),e_(i j)and u_i are all three kinds of independent functionsare suggested in this paper.It isproved that these two generalized variational principles areequivalent to each other if the stress-strain relation is satisfied as constraint.Some specialcases,i.e.generalized variational principles on nonlinear theory of elasticity with smalldeformation,on linear theory with finite deformation and on linear theory with smalldeformation together with the corresponding equivalent theorems are also obtained.All ofthem are related to the three kinds of independent variables. 相似文献
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This article addresses the three-dimensional stretched flow of the Jeffrey fluid with thermal radiation. The thermal conductivity of the fluid varies linearly with respect to temperature. Computations are performed for the velocity and temperature fields. Graphs for the velocity and temperature are plotted to examine the behaviors with different parameters. Numerical values of the local Nusselt number are presented and discussed. The present results are compared with the existing limiting solutions, showing good agreement with each other. 相似文献
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M. I. Ivanov 《Fluid Dynamics》2006,41(1):121-136
The natural harmonic oscillations of a heavy fluid in uniform-depth basins of complex shape, including those with three or more symmetry axes, are investigated within the shallow-water approximation. The waves are assumed to be gently sloping. The modes found are compared with the similar modes in an elliptic basin representing the class of basins with two symmetry axes. The mode characteristics associated with the number of basin symmetry axes and the basin shape are explored. Basins with two symmetry axes whose shape differs considerably from the elliptic, in particular, nonconvex basins, are considered. Both rotating and non-rotating basins are studied. The possibility of approximating the amplitudes of certain rotating-basin mode classes by Bessel functions is discussed. 相似文献
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IntroductionHyper_elasticmaterials ,suchasrubberandpolyurethane ,havemanyexcellentpropertiesandhavebeenusedwidelyinalmostallregionsofevery_daylifeandindustrialmanufacturing .Thevoidformationandgrowthinhyper_elasticmaterialsduetotheinstabilityofmaterialsplayafundamentalroleinthemechanismsofmaterialfractureandfailure.SotheproblemhasgotacertaindevelopmentinthepasttwentyyearsandtherecentreviewisthatofHorgan[1] .Chou_WangandHorgan[2 ] ,RenandCheng[3 ,4] studiedthegrowthofacentervoidinthecylindero… 相似文献
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In this paper a general technique for the analysis of nonlinear dynamical systems with periodic-quasiperiodic coefficients
is developed. For such systems the coefficients of the linear terms are periodic with frequency ω while the coefficients of
the nonlinear terms contain frequencies that are incommensurate with ω. No restrictions are placed on the size of the periodic
terms appearing in the linear part of system equation. Application of Lyapunov-Floquet transformation produces a dynamically
equivalent system in which the linear part is time-invariant and the time varying coefficients of the nonlinear terms are
quasiperiodic. Then a series of quasiperiodic near-identity transformations are applied to reduce the system equation to a
normal form. In the process a quasiperiodic homological equation and the corresponding ‘solvability condition’ are obtained.
Various resonance conditions are discussed and examples are included to show practical significance of the method. Results
obtained from the quasiperiodic time-dependent normal form theory are compared with the numerical solutions. A close agreement is found. 相似文献
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ADAPTIVE MESHLESS METHOD BASED ON LOCAL FIT TECHNOLOGY 总被引:1,自引:0,他引:1
LouLuliang ZengPan 《Acta Mechanica Solida Sinica》2005,18(2):164-172
An h-adaptive meshless method is proposed in this paper. The error estimation is based on local fit technology, usually confined to Voronoi Cells. The error is achieved by comparison of the computational results with smoothed ones, which are projected with Taylor series. Voronoi Cells are introduced not only for integration of potential energy but also for guidance of refinement.New nodes are placed within those cells with high estimated error. At the end of the paper, two numerical examples with severe stress gradient are analyzed. Through adaptive analysis accurate results are obtained at critical subdomains, which validates the efficiency of the method. 相似文献
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A singular function boundary integral method (SFBIM) is proposed for solving biharmonic problems with boundary singularities. The method is applied to the Newtonian stick–slip flow problem. The streamfunction is approximated by the leading terms of the local asymptotic solution expansion which are also used to weight the governing biharmonic equation in the Galerkin sense. By means of the divergence theorem the discretized equations are reduced to boundary integrals. The Dirichlet boundary conditions are weakly enforced by means of Lagrange multipliers, the values of which are calculated together with the singular coefficients. The method converges very fast with the number of singular functions and the number of Lagrange multipliers, and accurate estimates of the leading singular coefficients are obtained. Comparisons with the analytical solution and results obtained with other numerical methods are also made. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Three generalizations of classical hydrodynamic theories that are compatible with equilibrium thermodynamics and that are suitable for an appropriate macroscopic dynamical theory of polymeric liquids are considered. The strain tensor, the stress tensor and the chain segment distribution function (introduced in the network theory of polymeric liquids) are accepted as new state variables. We find that the generalized hydrodynamic equations are compatible with equilibrium thermodynamics provided certain conditions restricting the freedom of choice of constitutive relations are satisfied. In some particular cases the conditions are known from other considerations. We say that a dynamical theory is compatible with equilibrium thermodynamics, or equivalently, that it obeys the entropy principle if the properties listed in section 2.1 are satisfied. 相似文献