PRESSURE DISTRIBUTION ON THE GRIP ZONES IN THE CONFORM PROCESS

ＰＲＥＳＳＵＲＥＤＩＳＴＲＩＢＵＴＩＯＮＯＮＴＨＥＧＲＩＰＺＯＮＥＳＩＮＴＨＥＣＯＮＦＯＲＭＰＲＯＣＥＳＳＰＲＥＳＳＵＲＥＤＩＳＴＲＩＢＵＴＩＯＮＯＮＴＨＥＧＲＩＰＺＯＮＥＳＩＮＴＨＥＣＯＮＦＯＲＭＰＲＯＣＥＳＳ￥ＰｅｎｇＤａｓｈｕ（Ｄｅｐａｒｔｍｅ...     

板料成形过程数值模拟中的接触分析

根据板料成形过程中模具的运动特点,提出了全局搜索和局搜索的接触点搜索算法。建立了接触点的局部坐标系,并对特殊情况进行了适当处理,保证计算的连续性,建立了接触力学模型,分别采用罚函地和修正的库仑摩擦计算接触法向力和摩擦力,保证了接触计算的稳定性。     

Meshfree Method Numerical Simulation of Sheet Metal Forming Process

Metal forming plays an important role in manufacturing industry and is widely applied in industries. The traditional finite element method (FEM) numerical simulation is commonly used to predict metal forming process. Conventional finite element analysis of metal forming processes often breaks down due to severe mesh distortion, therefore time-consuming remeshing is necessary. Meshfree methods have been developed since 1977 and can avoid this problem. This new generation of computational methods reduces time-consuming model generation and refinement effort, and its shape function has higher order connectivity than FEM's. In this paper the velocity shape functions are developed from a reproducing kernel approximation that satisfies consistency conditions and is used to analyze metal tension rigid viscoplastic deforming and Magnesium Alloy (MB15) sheet superplastic tension forming. A meshfree method metal forming modeling program is set up, the partition of unity method is used to compute the integrations in weak form equations and penalty method is used to impose the essential boundary condition exactly. Metal forming examples, such as sheet metal superplastic tension forming and metal rigid viscoplastic tension forming, are analyzed to demonstrate the performance of meshfree method.     

Modeling and simulation of residual stresses during glass bulb pressing process

The residual stresses accumulated in the forming process have great effects on the product quality of the glass bulb. Based on the characteristics analysis of glass bulb forming, a mathematical model has been established for calculating residual stresses of glass pressing process. The material is assumed as thermorheologi-cally simple thermoviscoelastic material, and the flow-induced stress is neglected. The consequences of equilibrium and compatibility equations are discussed in detail, and the boundary conditions are specified for various stages of the forming process. The numerical solution is based on the theory of thin layers, combined with finite difference method in the time and layer difference in the thickness di-rection. The presented model and solution method could easily be extended to general pressing process of glass, and applied to problems relative to glass pressing, providing extensive reference values.     

刚塑性有限元法中的罚因子的选取

刚塑性有限元方法增量步长大,计算效率高,在金属塑性加工领域已得到越来越广泛的应用。罚函数法是刚塑性有限元中处理体积不变条件的常用方法。研究了罚函数法中罚因子对刚塑笥有限元法计算精度和计算效率的影响,得出在几种典型应力－应变模式下理想罚因子的选取方法,从布有助于更好的运用刚塑性有限元法模拟金属塑性加工过程。     

One-dimensional tensile constitutive equation cannot be directly generalized to deal with two-dimensional bulging mechanical problems

Superplastic forming has been extensively applied to manufacture parts and components with complex shapes or high-precisions. However, superplastic formation is in multi-stress state. In a long time, uniaxial tensile constitutive equation has been directly generalized to deal with multi-stress state. Whether so doing is feasible or not needs to be proved in theory. This paper first summarizes the establishing processes of superplastic tensile and bulging constitutive equation with variable m, and, using the analytical expressions of equivalent stress a and equivalent strain rate ε of free bulge based on the fundamentals of continuum medium plastic mechanics, derives the analytical expressions of optimum loading rules for superplastic free bulge. By comparing the quantitative results on typical superplastic alloy ZnAI22, it is shown that one-dimensional tensile constitutive equations cannot be directly generalized to deal with two-dimensional bulging quantitative mechanical problems; only superplastic b     

板料成形失稳内时理论分析

本文应用Valanis提出的新型内时本构方程，研究了板料成形的拉伸失稳问题，引入简单加载过程中应力、应变各主向及其增量成比例的特性，出单向和双向拉伸应力状态下的内时本构方程，据此分析了板料成形过程中的分散性失稳和集中性失稳问题，本文首先忽各非线性部分，推导出应用于拉伸失稳分析时内时理论的近似表达式，它对应于经典塑性理论解，然后在此基础上给出了内时理论的完整迭代数值解，结果表明内时本构理论具有很好的适用性。     

基于人工神经网络的锻造性能预报的研究

应用Ｇｌｅｅｂｌｅ－１５００热模拟试验机研究了１Ｃｒ１８Ｎｉ９Ｔｉ的热墩成形过程,得出了流动应力随变形条件的变化规律,测量了空冷后试件的硬度。首次采用人工神经网络对锻造性能进行预报,采用不同的改进ＢＰ算法加速了网络的收敛,得到了较好的网络信息,对１Ｃｒ１８Ｎｉ９Ｔｉ的锻造性能进行了较准确预报。     

金属板料二次成型的有限元分析

为了实现同台压力机加工多品种、多型号的板料,大型板料的成型采用同机分步成型,通过采用板料成型动力显式有限元模拟,采用四节点退化壳单元对板料进行离散化,利用中心差分法离散时间域,建立动力显式计算格式,采用罚函数法和修正库仑定理计算接触力和摩擦力.对二次成形过程,建立有限元分析计算模型,通过Dynaform软件仿真得出同机分步成形法的可行性.     

金属薄板台阶断面件可冷压加工性的试验研究

基于冲压分离工序只能实现板类零件的分离成形,且其分离断面为直壁形状,而现今生产实际中又提出了一种内孔和外缘均有台阶断面形状的薄板零件的要求,研发了一种以普通冲裁的冲压工艺为基础,与挤压、压印等冷锻工艺组合的板料成形新工艺,成形出了这种新型结构的薄板零件。利用DEFORM-3D等通用软件进行了数值模拟分析,获得了该类零件成形过程中的一些变形力学行为规律,并提出了其内孔与外缘之合理壁间距概念及其数值大小的设计原则,设计制造了一副冲压冷锻组合模,用铝质动力电池盖零件以及铜板材料进行了工艺试验验证