共查询到20条相似文献,搜索用时 187 毫秒
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采用面积坐标的四边形板弯曲单元 总被引:8,自引:5,他引:3
本文采用四边形面积坐标,并应用广义协调法构造出一个具有12个自由度的四边形板弯曲单元。单元的挠度场以面积坐标多项式表示,对应于直角坐标x,y的完全三次式和部分四次式,因而单元是完备的广义协调的板单元。应用的12个协调条件为挠度的四个点协调条件和四个边协调条件,以及法向转角的四个边协调条件。由于面积坐标和直角坐标之间为线性变换关系,因此单元刚度矩阵的推导相当简单。数值算例表明:本文单元具有高精度、收敛性、可靠性和对网格畸变不敏感的优点 相似文献
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两个采用面积坐标的四边形八结点膜元 总被引:4,自引:2,他引:2
本文采用文献(1)和(2)提出的四边形面积坐标法,并应用广义协调的概念,构造了两个新型四边形八结点膜元,数值算例表明:本文所提出的单元具有良好的性态,尤其当网络畸变时,单元依然保持良好的精度,其性能优于通常的八结点等参单元。 相似文献
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四边形单元面积坐标的微分和积分公式 总被引:18,自引:11,他引:7
构造四边形单元时,应用面积坐标方法有其优点。文献[1]系统地论述了四边形单元面积坐标理论,本文是文献[1]的续篇,补充论述采用四边形单元面积坐标时的微分和积分公式。采用三角形单元面积坐标时的微分和积分公式是其特殊情况。应用面积坐标方法时,易于得出四边形单元刚度矩阵的积分显式,无需依赖于数值积分,这个优点是采用四边形等参坐标时所不具备的。 相似文献
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文献建立了四边形单元的面积坐标系。本文在此基础上,利用边广义协调条件,构造了两个广义协调四边形单元,算例表明,它们是收敛的、可靠的。 相似文献
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采用面积坐标的广义协调四边形平面问题单元 总被引:1,自引:1,他引:0
文献「1」「2」建立了四边形单元面积坐标系,本文在此基础上,利用周广义协调条件,构造了两个广义协调四边形单元。算例表明,它们是收敛的,可靠的。 相似文献
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对平面四节点Q4单元采用优选的广义协调条件进行推导,将广义协调理论的应用拓展到最基本的平面问题单元。基于Q6以及QM6中基于内部参数的二次附加位移场,在Q4单元基础上增加满足广义协调条件的内参位移场,从而构造了一个满足广义协调条件的平面四节点等参元GQM6。数值算例表明,虽然采用了相同次数的位移场,但GQM6单元中采用的广义协调条件较QM6中采用的数值积分方法,可以进一步放松单元边界的约束,从而使单元的性能进一步提高,尤其在抗网格畸变能力方面。研究表明,将广义协调理论与一些传统单元进行深入融合仍然有着重要价值。 相似文献
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Song Cen Xiao‐Ming Chen C. F. Li Xiang‐Rong Fu 《International journal for numerical methods in engineering》2009,77(8):1172-1200
A novel strategy for developing low‐order membrane elements with analytical element stiffness matrices is proposed. First, some complete low‐order basic analytical solutions for plane stress problems are given in terms of the new quadrilateral area coordinates method (QACM‐II). Then, these solutions are taken as the trial functions for developing new membrane elements. Thus, the interpolation formulae for displacement fields naturally possess second‐order completeness in physical space (Cartesian coordinates). Finally, by introducing nodal conforming conditions, new 4‐node and 5‐node membrane elements with analytical element stiffness matrices are successfully constructed. The resulting models, denoted as QAC‐ATF4 and QAC‐ATF5, have high computational efficiency since the element stiffness matrices are formulated explicitly and no internal parameter is added. These two elements exhibit excellent performance in various bending problems with mesh distortion. It is demonstrated that the proposed strategy possesses advantages of both the analytical and the discrete method, and the QACM‐II is a powerful tool for constructing high‐performance quadrilateral finite element models. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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采用SemiLoof型约束条件的薄板矩形广义协调元 总被引:1,自引:1,他引:0
本文采用SemiLoof型约束条件,建立一个十二自由度的薄板矩形广义协调元。单元自由度只含角点位移,不含Loof结点位移、单元间的协调条件全部采用点型协调条件,不采用积分型协调条件。此单元吸取广义协调元和SemiLoof元的双重优点,消除其缺点,成为同类低阶薄板单元中的最优单元。 相似文献
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Chen Wanji Y. K. Cheung 《International journal for numerical methods in engineering》1999,46(3):433-455
Based on the refined non‐conforming element method, simple flat triangular elements with standard nodal displacement parameters are proposed for the analysis of shell structures. For ensuring the convergence of the elements a new coupled continuity condition at the inter‐element has been established in a weaker form. A common displacement for the inter‐element, an explicit expression of refined constant strain matrix, and an adjustable constant are introduced into the formulation, in which the coupled continuity requirement at the inter‐element is satisfied in the average sense. The non‐conforming displacement function of the well‐known triangular plate element BCIZ [1] and the membrane displacement of the constant strain triangular element CST [2] are employed to derive the refined flat shell elements RTS15, and the refined flat shell elements RTS18 is derived by using the element BCIZ and the Allman's triangular plane element [3] with the drilling degrees of freedom. A simple reduced higher‐order membrane strain matrix is proposed to avoid membrane locking of the element RTS18. An alternative new reduced higher‐order strain matrix method is developed to improve the accuracy of the elements RTS15 and RTS18. Numerical examples are given to show that the present methods have improved the accuracy of the shell analysis. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Z. F. Long 《Computational Mechanics》1992,10(3-4):281-288
Three generalized conforming elements for thin plate bending based on generalized compatibility conditions are derived: a triangular element with 9 d.o.f. (LT element) and two rectangular elements with 12 d.o.f. (LR-1 and LR-2). Their formulation is as simple as the conventional non-conforming element and they can be implemented in routine manner. By satisfying the generalized compatibility condition under constant moments, these new elements can always pass the patch test. Numerical examples show that high accurate result is obtained with fewer degrees of freedom by using these new elements of thin plate. 相似文献
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广义协调平板型三角形壳元 总被引:2,自引:1,他引:1
本文构造了一种具有三个角点十八个自由度的平板三角形壳元GST18。其拉伸与弯曲部分分别由含旋转自由度的三角形膜元和薄板弯曲三角形元组成。广义协调方法的采用,使得该单元的收敛性得到保证。在结点上引入了平面内旋转自由度,从根本上克服了单元共面刚度矩阵出现奇异这一困难。对平面膜元采用了缩减积分方案,使该单元不会产生薄膜闭锁现象。数值算例表明,本文提出的GST18薄壳元是计算精度优于同类单元的可靠、实用的单元。 相似文献
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T. L. Chang C.-L. Lee A. J. Carr R. P. Dhakal S. Pampanin 《International journal for numerical methods in engineering》2019,119(7):639-660
By utilizing a modified Hu-Washizu principle, a new mixed variational framework and a corresponding high-performing four-node membrane element with drilling degrees of freedom, named as GCMQ element, are proposed. In this work, the generalized conforming concept, which is originally proposed within a displacement-based formulation, is extended to a mixed formulation. The new element is able to handle higher-order displacement, strain, and stress distributions. The interpolations are complete up to second order for stress and strain. The enhanced strain field is optimized so that a complete cubic displacement field can be represented. For numerical integration, a five-point scheme is proposed to minimize computational cost. Compared to other four-node elements in existing literature, numerical examples show that the proposed element has a better performance regarding predictions of both displacements and internal forces, particularly with coarse meshes. The new element is also free from shear locking and volumetric locking. Due to the nature of the mixed framework, GCMQ can be directly used in elastoplastic applications. 相似文献
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G. F. Dargush P. K. Banerjee 《International journal for numerical methods in engineering》1992,33(4):695-717
A boundary element method is developed for problems of quasistatic axisymmetric thermoelasticity. Unlike previous approaches, this new time domain formulation is written exclusively in terms of surface quantities, thereby eliminating the need for volume discretization. Furthermore, since the exact three-dimensional infinite space fundamental solutions are employed, very accurate solutions are obtainable, including the determination of surface stresses. In the integral formulation, the fundamental solutions are separated into steady-state and transient components. The steady-state portion, which contains all of the singularities, is integrated analytically in the circumferential direction, yielding the familiar axisymmetric kernels. The remaining non-singular transient integrands are treated by a combination of analytical and numerical quadrature. The method is implemented in a general purpose boundary element code, which includes multiregion capability along with higher order conforming surface elements. Several numerical examples are provided to illustrate the validity of the formulation and the attractiveness of this approach for practical engineenring analysis. 相似文献
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J. C. Simo F. Armero 《International journal for numerical methods in engineering》1992,33(7):1413-1449
A class of ‘assumed strain’ mixed finite element methods for fully non-linear problems in solid mechanics is presented which, when restricted to geometrically linear problems, encompasses the classical method of incompatible modes as a particular case. The method relies crucially on a local multiplicative decomposition of the deformation gradient into a conforming and an enhanced part, formulated in the context of a three-field variational formulation. The resulting class of mixed methods provides a possible extension to the non-linear regime of well-known incompatible mode formulations. In addition, this class of methods includes non-linear generalizations of recently proposed enhanced strain interpolations for axisymmetric problems which cannot be interpreted as incompatible modes elements. The good performance of the proposed methodology is illustrated in a number of simulations including 2-D, 3-D and axisymmetric finite deformation problems in elasticity and elastoplasticity. Remarkably, these methods appear to be specially well suited for problems involving localization of the deformation, as illustrated in several numerical examples. 相似文献