表面机械研磨处理纯铜的宏细-观耦合数值研究

Macro-micro Coupled Simulation of Surface Mechanical Attrition Treatment of Copper

摘要:

发展一种耦合宏-细观的数值模拟方法，多尺度研究表面机械研磨处理（SMAT）纯铜的动态晶粒细化行为及残余应力状态。首先建立SMAT宏观有限元模型，计算SMAT细化的晶粒尺寸；然后根据平均晶粒尺寸建立细观多晶体模型，并将SMAT宏观有限元模型计算的滑移阻力导入到晶体塑性本构模型，同时将宏观模型输出的应变场转换成多晶体模型的位移边界条件；最后进行当前材料硬化状态下的晶体塑性有限元计算，进而分析宏观模型中一个材料点处细观组织结构的应力状态和晶粒取向分布。结果表明，在SMAT过程中，随着多弹丸不定向冲击次数的增加，纯铜表层细化的晶粒尺寸逐渐减小，表面宏、细观残余压应力逐渐增大，但晶粒取向分布的不均匀度呈现出先增大后减小的趋势。

Abstract:

A multi-scale study of the dynamic grain refinement behavior and residual stress state of copper induced by surface mechanical attrition treatment (SMAT) of copper was carried out by developing a macro-micro coupled simulation method. The three-dimensional macro-scale finite element model of SMAT was developed firstly, and the refined grain size was calculated accordingly. According to the averaged grain size, the finite element model of polycrystals was created, the dislocation slip resistance resulted from the macro-scale finite element computation of SMAT was imported into the crystal plastic constitutive model, and the strain field outputted from the macro-scale finite element simulation was converted into the displacement boundary condition and was imposed on the finite element model of copper polycrystals. The crystal plastic finite element computation was then performed with respect to the present material hardening effect. The microstructure stress state and grain orientation distribution within a material point of the macro-scale finite element model of SMAT were resultantly investigated by using the micro-scale finite element model of polycrystals. The obtained results show that, during the SMAT process, with the increasing of shot multi-directional impacts, the refined grain size decreases and both the macroscale and microscale surface compressive residual stresses increase, however, the non-uniformity of the grain orientation distribution increases at first and then decreases gradually.