板材冲压成形的晶体塑性有限元模拟

将率相关晶体塑性本构理论引入Mindlin曲壳单元模型与动力显式有限元法,采用切线系数法计算剪切应变率,根据晶体取向正态分布规律在单元积分点处分配晶体取向,按各晶体取向体积分数的加权平均计算多晶体应力,开发晶体塑性动力显式有限元程序,实现板材冲压成形过程模拟和晶体取向演化预示.以主要初始织构为铜织构和S织构的轧制铝板为对象,对方盒件冲压成形过程及织构演化进行数值模拟,计算结果与试验结果呈现出较好的一致性.通过晶体弹塑性有限元法不仅可以预示板材宏观成形构形变化,而且能够预测板材织构的演化情况.模拟结果显示在方盒件冲压成形过程中,铜织构和S织构为不稳定取向,变形后逐渐转到其他取向.

Finite Element Simulation of Sheet Metal Stamping with Polycrystalline Plasticity

The rate-dependent crystalline plasticity constitutive model is introduced into Mindlin shell element and dynamic explicit finite element method. A tangent modulus method is employed to calculate plastic strain increment. The crystal orientations are as- signed to finite element integration points and the stress of polycrystalline is calculated according to the normal distribution charac- teristic of orientation distribution function (ODF) in orientation space. A program is developed based on the proposed crystalline plasticity dynamic explicit finite element model to simulate sheet metal stamping as well as predict texture evolution. The stamping process of a rolled aluminum sheet, whose initial main textures are Cu and S texture for a square punch is numerically studied. The validity of proposed model is proved through the comparison between numerical results and experimental ones. By the crystalline plasticity finite element method, not only the sheet metal deformation process during stamping can be simulated, but also the evolu- tion of sheet metal texture can be predicted. During the box stamping process, Cu and S textures are not stable and transform to other orientations gradually.