共查询到20条相似文献,搜索用时 146 毫秒
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《计算机辅助设计与图形学学报》2014,(1)
针对任意单元形状和材料参数,通过引入附加节点和附加弹簧建立了一种三角形弹簧质点模型.首先给出弹簧刚度参数及附加节点坐标的解析公式,以实现有限元模型和弹簧质点模型三角形单元刚度矩阵的精确相等;然后考虑弹簧质点模型中可能出现的负刚度弹簧,进一步完善了弹簧质点模型形变计算方法.基于平面柔性体的数值模拟结果表明,文中提出的弹簧质点模型和形变计算方法精度好、效率高,且更具通用性. 相似文献
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在考虑陀螺力矩、转动惯量和剪切效应等影响因素下,采用Timoshenko梁理论并结合传递矩阵法给出了雾化器转轴的振动特性的计算方法.数值仿真部分采用二节点梁单元建立了雾化器转轴的有限元模型,并进行模拟,其结果验证了本文方法的有效性和高精度,讨论了转速、雾化轮质量以及陶瓷约束刚度等参数对雾化器转轴振动特性的影响. 相似文献
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卓家寿 《数值计算与计算机应用》1981,(4)
在有限单元法中,尤其是在选用参数型单元时,广泛应用数值积分去导出单元的荷载列阵和劲度矩阵.而在三角形单元、三棱柱单元或四面体单元中,积分公式常常采用借助自然坐标表示的Hammer积分公式: 相似文献
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针对一类规则QC-LDPC码,提出一种高效的Log-BP译码方法,通过矩阵分裂,将原监督矩阵分裂成多个小矩阵,将原本的校验节点更新运算拆分成多次处理,以降低log-BP迭代运算的复杂度,给出该方法的迭代运算顺序。与现有的log-BP译码方法相比,该方法在相同的码速率下,校验节点运算单元与变量节点运算单元总规模减小了1/3;在相同的硬件资源下,译码速率提高了1/3,且校验节点运算单元与变量节点运算单元结构趋于对称,有利于设置更少的流水线级数、获得更好的时钟性能。 相似文献
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一种网格和节点同步生成的二维Delaunay网格划分算法 总被引:1,自引:0,他引:1
应用Lawson算法对网格的Delaunay性质进行维护,利用单元尺度场控制生成网格的疏密分布;找到任一不满足尺度场要求的单元,在其可插度最大的边上按一定法则插入新节点,加密网格,实现内节点的生成与网格划分同步进行.该算法避免了搜寻包含三角形的过程,提高了效率.通过多次划分实验表明,该算法的时间复杂度约为O(N1.2).同时,由于在不满足单元尺寸要求的单元边上插入新节点,直接对单元的边长进行控制,使得网格的质量和自适性更加良好. 相似文献
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平面任意区域四边形网格自动生成的一种方法 总被引:9,自引:2,他引:9
在改进节点连接法的基础上,提出了一种平面任意区域的有限元网格全自动剖分方法,既能快速生成四边形单元网格,也能生成三角形单元网格; 相似文献
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Hao Yongping 《计算机辅助绘图.设计与制造(英文版)》1996,(1)
NORMALIZEDELEMENTNODETOPOLOGICALMATRIXOFFINITEELEMENTMESHESHaoYongpingAbstract:Onthebasisofconceptofelementnodetopologicalana... 相似文献
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《Computers & Structures》2007,85(7-8):404-418
In this paper, we study the convergence characteristics of some 3-node triangular shell finite elements. We review the formulations of three different isotropic 3-node elements and one non-isotropic 3-node element. We analyze a clamped plate problem and a hyperboloid shell problem using various mesh topologies and present the convergence curves using the s-norm. Considering simple bending tests, we also study the transverse shear strain fields of the shell finite elements. The results and insight given are valuable for the proper use and the further development of triangular shell finite elements. 相似文献
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David A Field 《Mathematics and computers in simulation》1983,25(6):485-488
This paper presents an algorithm determining the invertibility of any planar, triangular quadratic isoparametric finite element transformation. Extensions of the algorithm to three-dimensional isoparametric finite element transformations yield conditions which guarantee invertibility of 10-node tetrahedra and 8-node bricks. 相似文献
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Subhash C. Anand Roger H.H. Shaw 《Computer Methods in Applied Mechanics and Engineering》1978,15(1):1-12
Elastic-plastic finite element analyses using the Mises and Tresca yield conditions have become quite well-known since their introduction several years ago. Constant strain triangular (CST) elements have generally been utilized in these solutions.A 6-node linear strain triangular (LST) element with the capability of modeling partial plasticity is presented in this paper. A plane stress tensile specimen with a 90 degree notch subjected to a monotonically increasing load is solved by both the CST and LST element models within the inelastic range. It is shown that although the growth of plastic regions predicted by LST elements is smoother and more accurate when compared with those due to CST elements, there is a penalty to be paid in terms of the needed computer time. Consequently, unless very accurate strain and stress distributions are required in a specific problem, the use of CST elements in elastic-plastic analyses should be preferred. 相似文献
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《Computer Methods in Applied Mechanics and Engineering》2005,194(45-47):4607-4632
A simple displacement-based 3-node, 18-degree-of-freedom flat triangular plate/shell element LDT18 is proposed in this paper for linear and geometrically nonlinear finite element analysis of thin and thick laminated composite plates. The presented element is based on the first-order shear deformation theory (FSDT), and the total Lagrangian approach is employed to formulate the element for geometrically nonlinear analysis. The deflection and rotation functions of the element boundary are obtained from the Timoshenko’s laminated composite beam functions, hence convergence to the thin plate solution can be achieved theoretically and shear-locking problem is avoided naturally. The plane displacement interpolation functions of the Airman’s triangular membrane element with drilling degrees of freedom are taken as the in-plane displacements of the element. Numerical examples demonstrate that the present element is accurate and efficient for linear and geometrically nonlinear analysis of thin to moderately thick laminated composite plates. 相似文献
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An efficient facet shell element for corotational nonlinear analysis of thin and moderately thick laminated composite structures 总被引:1,自引:0,他引:1
In the present work, an efficient facet shell element for the geometrically nonlinear analysis of laminated composite structures using the corotational approach is developed. The facet element is developed by combining the discrete Kirchhoff-Mindlin triangular bending element (DKMT), and the optimal membrane triangular element (OPT). The membrane-bending coupling effect of composite laminates is incorporated in the formulation, and inconsistent stress stiffness matrix is formulated. Using corotational formulation and the proposed facet element, some example laminated composite structures with geometric nonlinearity are analyzed, and the results are compared with those found using other facet elements. 相似文献
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高次三角形单元在有限元计算中起着重要作用,本文提出一种画高次三角形单元云图的新方法。自然坐标系中的等腰直角三角形母元被均匀划分为N^2个等腰直角子三角形,根据映射到屏幕上的子三角形形心处的温度计算颜色,然后进行填充。实践表明,文中方法十分有效。 相似文献
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Song Cen Xiang-Rong Fu Ming-Jue Zhou 《Computer Methods in Applied Mechanics and Engineering》2011,200(29-32):2321-2336
By simply improving the first version of hybrid stress element method proposed by Pian, several 8- and 12-node plane quadrilateral elements, which are immune to severely distorted mesh containing elements with concave shapes, are successfully developed. Firstly, instead of the stresses, the stress function ? is regarded as the functional variable and introduced into the complementary energy functional. Then, the fundamental analytical solutions (in global Cartesian coordinates) of ? are taken as the trial functions for 2D finite element models, and meanwhile, the corresponding unknown stress-function constants are introduced. Thus, the resulting stress fields must be more reasonable because both the equilibrium and the compatibility relations can be satisfied. Thirdly, by using the principle of minimum complementary energy, these unknown stress-function constants can be expressed in terms of the displacements along element boundaries, which can be interpolated directly by the element nodal displacements. Finally, the complementary energy functional can be rewritten in terms of element nodal displacement vector, and thus, the element stiffness matrix of such hybrid stress-function (HS-F) element is obtained. This technique establishes a universal frame for developing reasonable hybrid stress elements based on the principle of minimum complementary energy. And the first hybrid stress element proposed by Pian is just a special case within this frame. Following above procedure, two 8-node and two 12-node quadrilateral plane elements are constructed by employing different fundamental analytical solutions of Airy stress function. Numerical results show that, the 8-node and 12-node models can produce the exact solutions for pure bending and linear bending problems, respectively, even the element shape degenerates into triangle and concave quadrangle. Furthermore, these elements do not possess any spurious zero energy mode and rotational frame dependence. 相似文献
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提出一种满足多种准则的动态搜索优化图象重建方法。从图象场的本质出发,设立了3个准则函数。熵函数的导数是非线性的,本文将其变换为近似的线性公式以获得迭代公路。动态搜索则尽可能避免很多算法在迭代过程中对图象校正过量或不足的问题。 相似文献
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The problem of topology optimization of 3D structures with design-dependent loading is considered. An algorithm for generating the valid loading surface of the 3D structure is presented, constituting an extension of the algorithm for 2D structures developed in Part I of this paper on the basis of a modified isoline technique. In this way the complicated calculation of the fit of the loading surface of a 3D structure may be avoided. Since the finite element mesh is fixed in the admissible 3D design domain during the period of topology evolution, the design-dependent loading surface may intersect the elements as the design changes. Independent interpolation functions are introduced along the loading surface so that the surface integral for generating the loading on the surface of the 3D structure can be performed more efficiently and simply. The bilinear 4-node serendipity surface element is constructed to describe the variable loading surface, and this matches well with the 8-node isoparametric 3D elements which have been used for the discretization of the 3D design domain. The validity of the algorithm is verified by numerical examples for 3D problems. Results of designing with design-dependent loads and with corresponding fixed loads are presented, and some important features of the computational results are discussed. 相似文献