共查询到19条相似文献,搜索用时 140 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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首先用Taylor展开随机无网格伽辽金法(Taylor expansion stochastic element-free Galerkin method,TSEFGM)进行随机结构分析.在无网格伽辽金法中,所求解问题的域由分布的节点表示,并采用移动最小二乘函数近似试函数.以及用罚函数法施加本质边界条件.同时利用Taylor展开法,建立随机结构分析的Taylor展开随机无网格伽辽金法;然后应用人工免疫遗传算法对结构可靠性进行分析.人工免疫遗传算法是一种新的综合人工免疫算法和遗传算法的智能优化算法,它避免了遗传算法易出现早熟、搜索效率低和不能很好地保持个体多样性等问题.数值实例表明,在随机结构与可靠性分析方面,Tlaylor展开随机无网格伽辽金法与人工免疫遗传算法具有明显的优势和广泛的应用前景. 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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结合微可压缩刚塑性材料的流动法则,利用局部加权残量法推导金属塑性成形过程的离散系统方程。采用径向基函数耦合多项式基函数构造无网格点插值法的形函数,用三次样条函数作为权函数。建立基于无网格局部径向基点插值法(local radial points interpolation method,LRPIM)的二维金属塑性成形离散控制方程,给出关键算法。径向基函数具有δ函数性质,因此可以很方便地施加本质边界条件。所有数值积分都在规则形状的局部域及其边界上进行,不需要积分背景网格,是一种真正的无网格法。对典型塑性成形过程进行LRPIM方法分析,并将数值结果与刚塑性有限元法计算结果和实验数据进行比较,结果吻合良好,表明所提方法的可行性和有效性。 相似文献
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Numerical simulation of three-dimensional bulk forming processes by the element-free Galerkin method
Yonghui Liu Jun Chen Song Yu Congxin Li 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):442-450
A new approach for simulating three-dimensional (3D) bulk metal forming processes is proposed by combining element-free Galerkin
method (EFGM) with the flow theory of 3D rigid-plastic/viscoplastic mechanics. Different from the conventional rigid-plastic
FEM, the velocity field is constructed by the moving least-squares (MLS) approximation. Special emphasis is placed on the
treatments of essential boundary conditions, incompressibility constraint and friction boundaries. The stiffness equation
for the analysis of 3D bulk metal forming using EFGM is derived and its key algorithms are given. To test the validity of
the proposed meshless approach, a typical 3D upsetting forming process is analyzed and the numerical results are compared
with those obtained by commercialized rigid-plastic FEM software Deform3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and
remeshing procedures unavoidable in conventional FEM, and still provides results that are in good agreement with finite element
predictions. 相似文献
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The necking of sheet metal is a main problem in forming processes that causes unacceptable thickness decreasing and leads to stop the process. There is a large amount of literature and research papers in this field. But the remaining problems to solve are the applicability and the accuracy of the methods for determining forming limits for various strain paths encountered in industrial processes. In the paper, we demonstrate that the linear stability analysis can provide accurate results considering various constitutive relationships and also considering that now the finite element analyses provide accurate results concerning the main field variables. The method is first presented, and then developments are done in the rigid-plastic case or in the rigid-plastic one accounting for damage by void growth. It is then demonstrated that the proposed method gives accurate results and then can be substituted to classical forming limit analyses. 相似文献
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三维体积成形过程的并行无网格法仿真分析 总被引:3,自引:0,他引:3
将显示无网格法引入三维体积成形仿真过程,设计了基于再生核质点法(Reproducing kernel particle method, RKPM)无网格法理论的并行算法。在前处理过程中,采用了多层次二分法对几何模型进行分区;在仿真计算过程中,设计基于消息传递机制的粗粒度并行程序,针对接触搜寻算法的特点,提出了接触问题并行化的新策略。并编制了相应的程序,成功地对三维体积成形问题进行了求解,准确地处理了网格严重畸变的问题,并验证了该算法的准确性和有效性。 相似文献
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A kinematical approach was proposed in a previous paper for predicting the optimal shape and the deformed length of a rigid-plastic metal sheet during cold-roll forming. Because the elastic effects are important in this kind of process, the method has been extended here to elastoplastic materials. In the new formulation, the sheet is still considered as a thin shell and its middle surface is described as a Coons patch depending on one geometrical parameter. Moreover, the material now satisfies a constitutive rate equation in which the corotational rate of stress is used. The Prandtl-Reuss model, including the von Mises yield criterion and the normality flow rule, is used. In order to integrate the elastoplastic constitutive equations, a radial return scheme is adapted so that the plastic power rate is calculated, using a Gauss method. Its minimization gives the optimal shape for a strain hardening elastoplastic material, as well as the optimal velocity field. This approach has been implemented on a workstation and, as for rigid-plastic materials, it gives a very fast simulation of the cold-roll forming process. 相似文献
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金属塑性成形过程CSPH无网格法数值模拟 总被引:2,自引:0,他引:2
应用微可压缩刚塑性材料的流动法则,采用修正的光滑粒子力学(Corrected smooth particle hydrodynamics, CSPH)无网格法,自行开发了求解金属方棒压缩和圆棒压缩等金属塑性成形过程应用程序。提出一种简单的求解体积应变速率的光滑技术,该技术使应力场计算结果能得到较好的改善。采用CSPH无网格法求解纯铝和Al6060铝合金材料压缩过程得到的速度场和应力场结果与有限元法计算结果以及试验数据进行了分析比较。结果表明, CSPH法能够较好地求解金属大变形过程,为今后进一步分析复杂金属变形问题提供了良好的研究手段。 相似文献
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Ping Lu Guoqun Zhao Yanjin Guan Xin Wu 《The International Journal of Advanced Manufacturing Technology》2011,53(5-8):485-503
The element-free Galerkin method is introduced into the analysis of three-dimensional bulk metal forming processes according to flow formulation for rigid/visco-plastic material. The transformation method is used to impose the essential boundary condition directly. The stiffness matrix equation is derived according to incomplete generalized variational principle. And the corresponding key simulation techniques are developed. The case that matrix A(x) appears irreversible is discussed, and the approaches for treating with this problem are given. Volumetric strain rate method is proposed for releasing the volume locking problem. The method for describing shapes of dies is presented. In order to impose arbitrarily shaped boundary conditions in three-dimensional problems, the local coordinate system is established and the transformation matrix between the local coordinate system and the global coordinate system is calculated. Methods for exerting velocity and frictional contact conditions are introduced. Dynamic adjustment techniques for the boundary of the workpiece including the contact/detachment judgment criterion and the method for modifying the contact nodes?? positions are given. Finally, the effectiveness of the method and key techniques is demonstrated by simulating a two-stage three-dimensional forging process. 相似文献
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基于刚塑性有限元法基本理论,并借助于通用三维有限元分析软件DEFORM-3D建立了花键冷滚压成形全过程三维动态有限元模型,对花键冷滚压成形过程进行了有限元模拟分析。揭示了花键冷滚压成形过程的等效应力、等效应变的分布情况和金属流动规律,从而为花键冷滚压成形工艺研究提供理论依据。 相似文献
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比较了有限元法与无网格法在金属成形应用中的优缺点,分析描述了无网格法在金属弹塑性变形、金属体积成形、板料成形等金属成形加工方面的应用现状,并阐述了无网格法的不足、亟待继续深入解决的问题以及未来的展望. 相似文献
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大变形成形过程刚塑性无网格伽辽金方法 总被引:5,自引:0,他引:5
在非稳态大变形塑性成形过程中,由于节点的大范围移动和流动的非均匀性,导致分析精度下降。针对移动最小二乘近似精度的提高,尤其是边界附近节点分析近似精度的提高,提出了相应的处理方案,以保证分析的精度。通过采用影响域节点控制方法以及边界节点分布密度动态控制方法,实现了塑性成形过程的无网格伽辽金方法的自适应分析。对拉普拉斯方程及典型的大变形成形过程进行了分析,通过与拉普拉斯方程解析解和相应的商品化刚塑性有限元软件Deform的分析结果进行对比,验证了处理方案的正确性。 相似文献