多晶铜表面织构冷压成形晶体塑性有限元分析

Crystal plasticity finite element analysis on cold pressing forming of surface texture of polycrystalline copper

基于晶体塑性理论和有限元方法建立了面心立方结构的纯铜材料的三维晶体塑性有限元模型,并对其钝化圆锥压头冷压成形过程进行了模拟。选取了平均晶粒尺寸分别为25、35和70μm的工件进行冷压,分析了成形过程中的载荷-压痕深度曲线、表面轮廓曲线、位移场与堆积现象、应力分布以及各滑移系的累积塑性应变。结果表明,晶粒尺寸越小,最大压痕深度处的峰值载荷越大,塑性回弹越大。冷压过程中,位移场产生堆积效应,在<110>晶向上最为明显,且体现了面心立方晶体的高度对称性。冷压后的工件表面发生细晶强化,使其具有更高的强度和硬度。随着各滑移系累积塑性应变的增加,8条滑移系被激活。随着晶粒尺寸的减小,应力云图开始离散,S12应力表现出与位移场相同的传导方向,平均晶粒尺寸为35μm时的工件残余应力最小。

Based on the crystal plasticity theory and finite element method,the 3D crystal plasticity finite element model(CPFEM)of pure copper material with FCC structure was established.The cold pressing forming process of the passivated conical indenter was simulated.The workpieces with average grain size of 25,35 and 70μm were selected for cold pressing,respectively,and load-indentation depth curves,surface profile curves,displacement field and accumulation phenomena,stress distribution and accumulated plastic strain of each slip system during forming process were analyzed.The results show that the smaller the grain size,the larger the peak load at the location with the maximum indentation depth and the higher the plastic springback.In the cold pressing process,the stacking effect of the displacement field occurs,which is the most obvious in the crystal direction of<110>,and the high symmetry of face centered cubic crystal is reflected.The refinement strengthening occurs on the surface of workpiece after cold pressing,which makes it has higher strength and hardness.With the increase of the accumulated plastic strain of each slip system,eight slip systems are activated.And with the decrease of grain size,the stress cloud diagrams begin to discrete.The S12 stress presents the same conduction direction as the displacement field,and the residual stress of the workpiece with the average grain size of 35μm is the minimum.