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为研究非比例加载条件下应变路径的变化对材料韧性所产生的影响,设计了一组包含宽应力三轴度的非比例加载试验,得到相应的载荷-位移/扭角曲线。运用ABAQUS/Explicit及用户子程序VUSDFLD,基于试验与模拟相结合的方法确定断裂起始点,研究复杂加载条件下断裂起始点的平均应力三轴度、罗德系数和等效断裂应变的变化趋势,分析应变路径变化对断裂成形极限的影响。结果表明:预加载的存在加快了断裂进程,且随着预加载程度的增加,材料的韧性断裂出现的愈早。对于拉-扭试验,在预扭阶段应变沿着纯扭趋势发展,而进入拉伸阶段后应变并非沿着单拉的应变路径进行变化;对于压-扭试验,在预压阶段应变沿着单向压缩的应变路径变化,而扭转阶段则沿着平行于纯扭的应变路径变化。
In order to study the effect of strain path change on the material toughness under non-proportional loading conditions, a set of non-proportional loading tests including three axes of wide stress were designed and the corresponding load-displacement / twist curves were obtained. ABAQUS / Explicit and user subroutine VUSDFLD were used to determine the starting point of fracture based on the combination of test and simulation. The mean stress triaxiality, Rhodes coefficient and equivalent strain at break of fracture initiation point under complex loading conditions were studied. The influence of strain path change on fracture forming limit was analyzed. The results show that the existence of preloading accelerates the fracture process, and the premature loading increases the ductile fracture of the material. For the pull-torsion test, the strain develops along the purely twisting trend during the pre-twisting phase and does not change along the single-pull strain path after entering the drawing stage. For the compression-torsion test, The compressive strain path changes while the torsional phase changes along the strain path parallel to the pure torsion.