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刚塑性有限元模拟中罚因子的取值 总被引:6,自引:1,他引:5
在采用罚函数法的刚塑性刚粘塑性有限元模拟中,罚因子的大小代表对金属体积变化的惩罚的强弱程度,取值不当将影响模拟精度和解的收敛性。本文通过实际计算分析了罚因子与体积变化之间的关系,并提出了一种简单有效的方法,来确定罚因子的合理取值范围。 相似文献
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运用一种基于全量理论的多步有限元方法计算分析了金属体积成形过程.该方法针对刚塑性不可压缩材料,在静力平衡条件下以约束变分原理通过最小化近似塑性势能进行有限元求解.多步模拟在各中间构形的虚拟滑动约束下沿变形路径进行分步迭代计算,考虑了接触和变形历史,能够快速模拟较复杂的体积成形问题.运用该方法对几个典型金属体积成形过程进行了正向一步和多步数值模拟,将计算结果与增量有限元法计算结果进行了比较.结果表明:在计算金属体积成形过程中,基于全量理论的多步有限元模拟能够在大大缩短计算时间的同时获得与增量法计算结果相比偏差小于10%的计算结果. 相似文献
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简单介绍在塑性有限元方法中引入成形过程材料体积不变条件方法的基础上,针对目送2塑性有际元模拟软件中存在的材料体积损失的问题,研究了影响体积损失的因素及其关系,给出了减少体积损失的措施。 相似文献
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电磁成形是一种高速率成形方法,它能够有效提高金属板材的成形极限。但是电磁成形过程复杂,涉及到磁场?结构场之间的耦合分析。数值模拟提供一种手段去解决耦合问题。然而,大多数的数值模拟都限于2D。建立3D有限元模型去分析电磁平板胀形。成形过程中考虑了板料与底模的接触和板料变形对磁场的影响。板料中心节点和半径20mm处节点的位移随着时间的变化与实验结果一致。分析了塑性应变能和塑性应变。 相似文献
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基于有限元分析的摩擦系数测定 总被引:2,自引:2,他引:0
在塑性体积成形有限元模拟中,摩擦模型和摩擦系数的确定是一个关键问题.本文采用圆环镦粗法研究体积成形中摩擦系数的确定.利用有限元分析确定一组摩擦系数标定曲线,用圆环镦粗试验确定圆环内径变化率百分比与圆环高度压缩百分比关系曲线.通过曲线对比得到模具材料和成形材料之间的摩擦系数.针对6A02CZ材料在钢模具中体积成形时6A02CZ材料与钢之间的摩擦系数进行确定,6A02CS材料在无润滑剂和润滑油做润滑剂两种情况下的摩擦系数分别为0.325和0.3.研究表明,采用有限元方法和圆环镦粗试验相结合的方法更适合塑性体积成形中的有限元分析. 相似文献
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基于有限元和最优化方法的淬火冷却过程反传热分析 总被引:7,自引:0,他引:7
淬火过程换热系数的求解是反向热传导问题中的一种不适定和非线性问题.本文提出了一种求解淬火过程随温度变化的换热系数的新方法,该方法把有限元方法引入反向热传导问题,根据实验测量的温度曲线,结合使用最优化方法中的进退法和试探法确定合理的边界换热系数.为了使进退法适用于该类反传热问题,对其算法进行了改进,并用其确定换热系数优化的搜索区间,然后用试探法(黄金分割法)在搜索区间内找到换热系数的最佳值.在计算过程中,利用有限元法可以方便地计算出各个单元在整个过程的相变情况,得到各单元在相应时间段所产生相变潜热,并将各单元的相变潜热与单元温度场进行耦合计算. 相似文献
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Guoqun Zhao Ed Wright Ramana V. Grandhi 《International Journal of Machine Tools and Manufacture》1995,35(9)
This paper presents a preform design method which employs an alternative boundary node release criterion in the finite element simulation of backward deformation of forging processes. The method makes use of the shape complexity factor which provides an effective measure of forging difficulty. The objective is to release die contacting nodes in a sequence which will minimize the geometric complexity throughout the backward deformation simulation. This is done by calculating the effect of releasing each of a select group of boundary element nodes at each finite element solution step. The particular detached node which results in the minimum shape complexity factor will be released for the current step. This process continues for each backward step until the last few nodes remain in contact. This design method is demonstrated through the simulated forging of an integrated blade and rotor turbine disk blank. A preform shape developed by this method is compared with an empirically designed preform. Performance parameters for comparison include die fill, flash volume, effective strain variance, frictional power and die load. Comparing the results of the forward simulations indicates improved performance of the preform design using FEM based backward deformation method over that of the empirical design. 相似文献
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ANALYSIS OF THREE-DIMENSIONAL UPSETTING PROCESS BY THE RIGID-PLASTIC REPRODUCING KERNEL PARTICLE METHOD 总被引:1,自引:0,他引:1
Y. H. Liu J. Chen S. Yu X. W. Chen 《金属学报(英文版)》2006,19(5):371-378
A meshless approach, called the rigid-plastic reproducing kernel particle method (RKPM), is presented for three-dimensional (3D) bulk metal forming simulation. The approach is a combination of RKPM with the flow theory of 3D rigid-plastic mechanics. For the treatments of essential boundary conditions and incompressibility constraint, the boundary singular kernel method and the modified penalty method are utilized, respectively. The arc-tangential friction model is employed to treat the contact conditions. The compression of rectangular blocks, a typical 3D upsetting operation, is analyzed for different friction conditions and the numerical results are compared with those obtained using commercial rigid-plastic FEM (finite element method) software Deform^3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and remeshing procedures which are unavoidable in conventional FEM and can provide results that are in good agreement with finite element predictions. 相似文献
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利用热力耦合有限元方法,对薄带连铸结晶辊的温度场和热变形进行研究,给出了浇注温度、浇注速度和冷却水流量对结晶辊温度场和热变形的影响规律,并利用有限元方法设计了初始辊形,有效地改善了铸带厚度的均匀性. 相似文献