基于晶体塑性的复杂应力下钢轨钢微孔洞演化行为研究

Study on Evolution Behavior of Microvoid of Rail Steel under Complex Stress Based on Crystal Plasticity

采用晶体塑性有限元方法研究复杂应力下的珠光体钢轨钢微孔洞演化行为,分析应力三轴度和洛德参数对体心立方晶体单晶中孔洞生长和合并的影响。在研究中,进行纳米压痕试验和电子背散射衍射,获得压痕处的晶体取向,采用晶体塑性有限元方法和用户自定义材料子程序标定晶体塑性材料参数,并采用代表性体元法分析不同应力三轴度和洛德参数对体心立方晶体单晶中微孔洞演化的影响。研究结果表明,不同应力三轴度和洛德参数组合的变形模式对钢轨钢微孔洞的演化具有竞争性影响。对于低应力三轴度,变形模式主要由洛德参数决定。随着应力三轴度的增大,应力三轴度对钢轨钢微孔洞演化的影响逐渐占主导作用。通过研究还发现,在不同应力三轴度和洛德参数影响下,体心立方晶体单晶晶内基体材料的有效应力演化规律与整体胞元的等效应力相反。

The crystal plastic finite element method was used to study the microvoid evolution behavior of pearlitic rail steel under complex stress,and the effects of stress triaxiality and Lode parameter on the growth and merger of pores in body-centered cubic crystal single crystal were analyzed.In this study,nanoindentation test and electron backscatter diffraction were carried out to obtain the crystal orientation at the indentation,the crystal plastic finite element method and user-defined material subprogram were used to calibrate the crystal plastic material parameter,and the representative bulk element method was used to analyze the effects of different stress triaxiality and Lode parameter on the evolution of microvoid in body-centered cubic crystal single crystal.The results show that the deformation mode of different stress triaxiality and Lode parameter combination has a competitive influence on the evolution of rail steel microvoid.For low-stress triaxiality,the deformation mode is mainly determined by the Lode parameter.With the increase of stress triaxiality,the influence of stress triaxiality on the evolution of microvoid of rail steel gradually dominates.Through the study,it is also found that under the influence of different stress triaxiality and Lode parameter,the effective stress evolution law of the body-centered cubic crystal single crystal matrix material is opposite to the equivalent force of the whole cell.