中文摘要：

针对预拉伸和预扭转变形后的拉扭组合实验,用多晶集合体模型为代表性单元,结合晶体塑性理论对多晶Cu进行了晶粒尺度的屈服特性研究,采用子模型法对晶粒尺度的代表性单元模型和多晶Cu试样拉扭实验进行跨尺度材料力学行为分析.结合对多晶集合体的后继屈服面形状及演化趋势的研究,探讨不同加载路径和不同屈服点定义对材料后继屈服面的影响;通过对不同加载路径多晶Cu非均匀性的统计分析,探讨加载历史对多晶材料细观塑性变形不均匀性的影响.分析结果表明：后继屈服面的形状和尖角效应的出现与预加载方向和屈服定义有关;加载路径不同,多晶体内变形不均匀性的差异很大.运用子模型的晶体塑性模拟与后继屈服实验的结果有较好的一致性.

英文摘要：

Combined tension-torsion test under pre-tension and pre-torsion deformation,the yield characteristics of polycrystalline copper in grain scale was investigated by crystal plasticity theory associated with polycrystalline aggregate model.Through a sub-model method,the cross scale analyses of mechanical behavior of polycrystalline copper by the calculations using a representative volume element（RVE） and a specimen under tension and torsion were carried out.Based on the research on the shape and the evolution of a subsequent yield surface,the effects of different loading paths and yield definitions on the subsequent yield surface were explored.The heterogeneous statistical analysis of the polycrystalline copper under different loading paths was also performed.And further more,the effects of loading history on the subsequent yield surface,and on the micro heterogeneous distribution were estimated.The numerical results show that the shape of the subsequent yield surface and the appearance of yield surface corner are related to the pre-loading direction and the different yield definitions,the heterogeneous deformation in polycrystal under different loading paths is very various.The results by the analysis based on crystal plasticity calculation combined with the sub-model method are compared with experimental results and they are in reasonable agreement.