共查询到20条相似文献,搜索用时 62 毫秒
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A 3-D multilayer hybrid element is developed for the analysis of thick laminated plates and shells. The stresses are assumed independently in each sublayer element and the stress continuity between adjacent sublayers is applied to form the stress pattern of the multilayer element. Both interlaminar stress concentration and global structure response can be adequately predicted by the element model. The buckling analysis of orthotropic cylindrical shells under the external pressure is performed and the results show that the plane strain assumption is not applicable to the buckling of long orthotropic cylindrical shells. 相似文献
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一种三维体罚平衡应力杂交元 总被引:1,自引:0,他引:1
主要研究三维体罚平衡杂交元理论并建立相应的单元模型,采用罚平衡方法可以在不增中自由度的前提下,有效地扼制寄生应力,从而大幅度提高畸变网格下的计算精度,所给算例对8节点空间六面体单元(DM8)、优化杂交元和该文得出的单元进行了比较,证明了这一点,文中还尝试将该文 于方板和不可压缩问题的计算,得出了令人满意的结果。 相似文献
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杂交元本征应力模式和应力子空间的性质研究 总被引:3,自引:0,他引:3
详细讨论了有限元本征应力模式和应力子空间的性质,并着重讨论和进一步完善了与杂交应力有限元应力子空间有关的一些定理,为提出新方法提供了理论基础,主要包括:(1)证明了杂交元特征值不大于对应位移元的特征值;(2)证明了矩阵H非奇异的充分必要条件是假设应力模式线性无关;(3)证明了杂交元所对应位移元的本征应力模式形成的杂交元与该位移元相同;(4)证明了等价假设应力模式形成相同的杂交元;(5)证明了确定杂交元本征应力模式的充分必要条件是其范数平方等于所形成杂交元的变形模态特征值;(6)证明了杂交元假设应力模式与变形模态的能量一一对应的充分必要条件是假设应力模式彼此正交且与所对应位移元的本征应力模式除了一一对应者之外都正交。 相似文献
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建立了一个新的求解带圆孔薄板弹性问题的二维杂交应力单元,该单元为四节点四边形平面单元,名为P-HS4-8β。由极坐标系下的物理方程和几何方程求解出了一个极坐标方向的应力,通过将这个应力带入由Hellinger-Reissner原理推导的极坐标系下平面应力问题的能量方程中,得到了消除了该应力的能量方程,基于这个能量方程建立了杂交应力单元列式。根据圆孔边无外力条件和相容方程,推导了适用于求解带圆孔薄板问题的极坐标系下的二应力插值矩阵,并将此矩阵应用于新的有限单元列式中。数值算例表明新单元在求解孔边附近的应力时具有较高的精度。 相似文献
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The delay of the onset of localization and the post-necking behaviour for stretched thin sheets are determined by three-dimensional effects. Thus, a 2-D finite element analysis based on a local plasticity theory will give a physically unrealistic mesh dependent solution. This, in spite of the fact that the stress state, is essentially two-dimensional. By incorporating a length scale with relation to the thickness of the sheet, it is demonstrated how a 2-D finite element analysis based on a gradient dependent plasticity theory can give a good approximation of the post-necking behaviour. This is illustrated by numerical comparison of results from a full 3-D finite element analysis, with results from a 2-D finite element model based on a finite strain version of a gradient dependent J2-flow theory. Some numerical problems in the modeling will be discussed briefly. 相似文献
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《International Journal of Solids and Structures》2014,51(23-24):4015-4025
In this paper, a gradient-enhanced 3-D phenomenological model for shape memory alloys using the non-local theory is developed based on a 1-D constitutive model. The method utilizes a non-local field variable in its constitutive framework with an implicit gradient formulation in order to achieve results independent of the finite element discretization. An efficient numerical approach to implement the non-local gradient-enhanced model in finite element codes is proposed. The model is used to simulate stress drop at the onset of transformation, and its performance is evaluated using different experimental data. The potential of the presented numerical approach for behavior of shape memory alloys in eliminating mesh-dependent simulations is validated by conducting various localization problems. The numerical results show that the developed model can simulate the observed unstable behaviors such as stress drop and deviation of local strain from global strain during nucleation and propagation of martensitic phase. 相似文献
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封隔器卡瓦接触应力研究 总被引:4,自引:0,他引:4
封隔器上的卡瓦锚定后起到支撑封隔器、锁定胶皮筒的作用,其性能好坏直接影响到油井的产量和生产安全。卡瓦与套管间的咬合力分布决定了封隔器在使用中的成败。咬合力的分布是否合理,将直接关系到套管的损伤程度及卡瓦的寿命。文中同时应用有限元法和三维光弹性技术对封隔器卡瓦进行了接触应力分析,介绍了实验模型的建立和实验步骤以及计算模型的建立和边界条件的考虑,比较了数值计算与三维光弹实验的结果,分析了造成误差的原因。实验应力分析结果为有限元计算模型的建立及边界条件的确定提供了重要的实验保证。研究工作获得了一些重要的结果,为封隔器卡瓦的优化设计提供了相关的参数。 相似文献
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构造了一种新的三维奇异单元,提出了一种有效计算三维裂纹应力强度因子新的数值方法。该方法的计算结果与理论解和Newman解结果一致;与Panson等方法相比所使用的自由度数大大减小。结果表明该方法是一种高效、稳定可靠的计算方法。 相似文献
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根据Hellinger-Reissner原理建立了具有一个无外力圆柱表面的三维八节点杂交应力元,其假设应力场严格满足柱坐标下三维平衡方程及圆柱面上无外力边界条件;当元退化为二维时也满足协调方程。数值算例表明,这种特殊杂交应力元可高效地分析具有两个圆孔薄板和厚板的应力集中,特别是三维应力集中。 相似文献
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J.-Y. Cho A.V. Idesman V.I. Levitas T. Park 《International Journal of Solids and Structures》2012,49(14):1973-1992
A finite element approach is suggested for the modeling of multivariant stress-induced martensitic phase transitions (PTs) in elastic materials at the nanoscale for the 2-D and 3-D cases, for quasi-static and dynamic formulations. The approach is based on the phase-field theory, which includes the Ginzburg–Landau equations with an advanced thermodynamic potential that captures the main features of macroscopic stress–strain curves. The model consists of a coupled system of the Ginzburg–Landau equations and the static or dynamic elasticity equations, and it describes evolution of distributions of austenite and different martensitic variants in terms of corresponding order parameters. The suggested explicit finite element algorithm allows decoupling of the Ginzburg–Landau and elasticity equations for small time increments. Based on the developed phase-field approach, the simulation of the microstructure evolution for cubic-tetragonal martensitic PT in a NiAl alloy is presented for quasi-statics (i.e., without inertial forces) and dynamic formulations in the 2-D and 3-D cases. The numerical results show the significant influence of inertial effects on microstructure evolution in single- and polycrystalline samples, even for the traditional problem of relaxation of initial perturbations to stationary microstructure. 相似文献
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涂层厚度对硬脆涂层结合强度的影响 总被引:1,自引:0,他引:1
应用有限元分析的方法分析二维模型涂层层数以及涂层厚度对涂层/基体结合强度的影响已得到广泛研究。然而二维模型相比三维模型未能考虑宽度方向应力应变的影响,导致求解精度低。因此对三维模型涂层层数以及厚度对涂层/基体结合强度影响的研究显得实为重要,但这方面研究比较少。本文建立有限元三维模型,通过比较有限元模拟结果与赫兹接触精确解析解验证了模型的可靠性,讨论了涂层厚度对涂层/基体界面最大剪切力影响关系。结果表明,剪应力最小值随着涂层厚度的增加逐渐减小,然而剪应力最大值却随着厚度的增加先减小后增大,在0.4mm时取得最小值;随着涂层厚度的增加,涂层/基体结合处剪应力Z方向突变减小,涂层内部剪应力Z方向突变增大,但是突变位置向涂层表面靠近,而且涂层/基体结合处X方向的剪应力变化随着涂层厚度增加趋于平缓。 相似文献
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复合材料中矩形夹杂角端部力学行为分析 总被引:1,自引:1,他引:0
提出了一种分析矩形夹杂角端部奇异应力场的新型杂交有限元方法,该方法在分析矩形夹杂角端部奇异应力场时,需要在夹杂端部构造一个超级单元。超级单元的刚度矩阵可以通过夹杂端部特征问题数值解建立。我们用这种方法计算了单向载荷作用下无限大均质板中单个矩形夹杂角端部奇异应力场,并与现有的数值解进行了比较。比较结果表明:本文提出的方法是可行的、有效的,而且数值结果精度高。为说明本文方法适用范围更广,文章最后讨论了各向异性弹性材料和横观各向同性压电材料中矩形夹杂角端部电弹性场行为。 相似文献
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Tian Zongshu 《Acta Mechanica Sinica》1988,4(1):35-44
A series of axisymmetric solid-of-revolution elements with 8-node and quadrilateral cross section have been developed based
on the assumed stress hybrid model. A quadratic boundary displacement assumption is employed for each element and a variety
of interior stress assumptions have been made. Two different kinds of procedure used for developing stress field have been
studied. Example problems of a thick-walled cylinder under internal pressure and a thick-walled sphere under internal pressure
are utilized to evaluate the various elements and a desirable stress assumption has been identified. Comparisons of present
results with those obtained by the use of 8-node element based on the assumed displacement model indicate that this hybrid
stress element is far superior in predicting the stress distribution. 相似文献