共查询到17条相似文献,搜索用时 234 毫秒
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在国家杰出青年科学基金资助项目《塑性加工工艺及设备》(No.50425517),以及国家自然科学基金资助项目《金属体积成形过程的刚(粘)塑性无网格伽辽金方法数值模拟理论及其关键技术研究》(No.50575125)支持下,开展刚(粘)塑性无网格伽辽金方法及其关键技术与应用的研究报告,对刚(粘)塑性无网格伽辽金方法的基础理论、数学模型建立方法、关键处理技术在金属塑性成形过程中应用研究的成果。 将无网格伽辽金方法引入塑性成形过程模拟,提出基于刚(粘)塑性理论的无网格伽辽金方法,推导刚度矩阵方程和求解列式。利用变换法施加本质边界条件,采用反正切摩擦模型描述摩擦力边界条件。对于模具边界任意的塑性成形过程,在局部坐标系下施加摩擦力边界条件,给出局部坐标系和整体坐标系的变换矩阵,解决了模具形状任意的二维塑性成形问题摩擦力边界条件的施加问题。采用直接迭代法获得初始速度场,利用Newton Raphson迭代方法求解刚度方程,给出模拟等温塑性成形问题的分析步骤。对于中高温条件下的塑性成形过程,推导出刚(粘)塑性无网格伽辽金方法热力耦合分析模型,给出热力 相似文献
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针对Inconel690镍基高温合金圆管挤压变形过程,推导建立圆柱坐标系下无网格伽辽金(Element-free Galerkin,EFG)法的求解模型并编制软件程序,采用Gleeble-1500热模拟机试验建立Inconel690的本构模型,实现了对于Inconel690镍基高温合金圆管挤压变形行为的数值模拟。所开发的EFG方法,采用罚函数法施加本质边界条件,利用反正切摩擦模型计算边界摩擦力,应用Newton-Raphson迭代方法求解刚度方程。为了验证所建EFG方法及软件,通过多次随机选取变形区内若干节点,提取其速度场、等效应变速率和等效应力的计算值,并与相同工况下的DEFORM有限元计算结果进行对比,最大的相对差不大于8%;将仿真计算得到的稳态挤压力与某工厂同样工况条件下的挤压力实测值相比较,最大的相对差小于7%。运用所建立的EFG方法求解模型和软件,仿真研究Inconel690高温合金圆管挤压过程,求得稳态挤压力、速度场、等效应变速率场以及等效应力场,分析获得塑性变形区内金属变形规律;并以某工厂的挤压机为对象,以挤压力最小为优化目标,借助正交试验法设计模拟计算工况,得到了较优的挤压工艺参数。 相似文献
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无网格伽辽金方法在线弹性断裂力学中的应用研究 总被引:2,自引:2,他引:0
通过对移动最小二乘形函数进行局部修正,将混合变换法应用于无网格伽辽金方法,给出分析线弹性断裂力学问题的有效的无网格伽辽金方法。这一方法克服了无网格伽辽金方法中常用的拉格朗日乘子法和罚函数法的缺点,实现了本质边界条件在节点处的精确施加。运用线弹性断裂力学理论,采用基于t-分布的新型权函数和部分扩展基函数,对有限板单边裂纹的应力强度因子和拉剪复合型裂纹的扩展进行分析。由于该方法仅需节点信息,而不需要节点的连接信息,从而避免了有限元方法中的网格重构,大大简化了裂纹扩展的分析过程。数值计算结果表明了方法的有效性。 相似文献
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《Tribology - Materials, Surfaces & Interfaces》2013,7(2):87-97
AbstractThis paper presents an h-adaptive element free Galerkin (EFG) model and its formulation based on stain energy gradient for solving elastoplastic contact problems. In this model, the element free Galerkin finite element (EFG–FE) coupling method uses the initial stiffness method, and an error estimation approach based on strain energy gradient and a local adaptive refinement strategy are combined. Two-dimensional elastic contact problem between a rigid cylinder and an elastic plane is analysed to validate the adaptive elastoplastic EFG model. The results indicate that the adaptively refined solutions are accurate as compared to the Hertz theoretical solution or the uniformly refined solutions, while the cost of CPU time used by the adaptive model is less than that by the uniformly refined model under the same condition. Furthermore, the elastoplastic contacts involving a rough surface of elastic perfectly plastic and elastoplastic properties are investigated. 相似文献
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利用有限元法分析金属的刚塑性问题时,在变形的高梯度区域单元容易严重畸变,这极大地降低了分析精度.在刚塑性有限元方法的框架中,文中根据计算增量步的网格质量,提出金属刚塑性有限元和无网格迦辽金法的自动耦合算法,在单元严重畸变的区域转换为无网格迦辽金法进行计算.数值实例表明:算法在很大程度上既保持了有限元法的计算效率,又能够... 相似文献
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结构形状优化已经在工程应用中得到重视,将无网格法与形状优化相结合能够从根本上解决优化过程中出现的有限单元扭曲或畸变问题。为此在无网格Galerkin法的基础上,利用离散导数法,提出一种基于离散型的节点位移灵敏度分析方法,其中采用了拉格朗日乘子法来施加本质边界条件。该方法的最大优势是求解过程与无网格Galerkin法的求解过程相似,容易实现。另外对形状优化的数学模型和节点位移的设计速度域进行了讨论。采用具有解析解的实例,对所提出的灵敏度分析方法进行了验证,所得结果显示两者非常吻合。利用上述所建立的形状优化算法,完成了两个工程实例的形状优化设计。 相似文献
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In this work, a new penalty formulation is proposed for the analysis of Mindlin-Reissner plates by using the element-free
Galerkin method. A penalized weak form for the Mindlin-Reissner Plates is constructed through the exterior penalty method
to enforce the essential boundary conditions of rotations as well as transverse displacements. In the numerical examples,
some typical problems of Mindlin-Reissner plates are analyzed, and parametric studies on the order of integration and the
size of influence domain are also carried out. The effect of the types of background cells on the accuracy of numerical solutions
is observed and a proper type of background cell for obtaining optimal accuracy is suggested. Further, optimal order of integration
and basis order of Moving Least Squares approximation are suggested to efficiently handle the irregularly distributed nodes
through the triangular type of background cells. From the numerical tests, it is identified that unlike the finite element
method, the proposed element-free Galerkin method with penalty technique gives highly accurate solution without shear locking
in dealing with Mindlin-Reissner plates. 相似文献
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Thomas E Blejwas 《Mechanism and Machine Theory》1981,16(4):441-445
In the Lagrange multiplier method, the motion of each element is represented in terms of its own rigid-body and flexible body generalized coordinates. The elements are treated as uncoupled from each other except for the application of interaction forces (the Lagrange multipliers) which enforce constraint conditions between the elements. Rather than eliminating the multipliers and obtaining coupled system coordinates, the values of the Lagrange multipliers are solved in time as part of a numerical technique. The multipliers are applied in turn to the individual elements and the simulation proceeds to the next point in time using numerical integration.The method of solution is applied to an illustrative example, a slider-crank mechanism. Modeling considerations and appropriate kinematic constraints are discussed. The author hopes to present numerical results for this example at the conference. 相似文献