一种基于损伤机制的刻痕膜片断裂行为数值计算方法

A mechanism based approach to simulate the ductile fracture of pre-notched metal diaphragm

针对刻痕膜片结构的断裂问题,提出了一种适合拉剪混合断裂模式修正的(Gurson-Tvergaard-Needleman, GTN)模型,在屈服势中使用孔洞体积分数和剪切损伤变量分别表征拉伸和剪切损伤机制引起的材料刚度下降及失效过程,建立了两个损伤参数率形式的累积方程。基于ABAQUS的用户子程序开发出双损伤变量GTN损伤材料本构,对刻痕膜片的破裂过程进行计算分析,得到了破裂压力的精确计算值。借助于软件的失效单元删除功能,模拟出了裂纹在刻痕膜片中的萌生、扩展以及最终断裂过程。与试验结果的对照表明,模型能够准确模拟出刻痕膜片的破裂压力及断裂过程,可广泛用于模拟拉剪混合载荷模式下的韧性金属断裂过程。

A new modification to Gurson-Tvergaard-Needleman(GTN)model was proposed for the simulation of ductile fracture behaviors under combined tensile and shear loading mode in pre-notched metal diaphragm.Two distinctive damage parameters,respectively related to tensile and shear damage mechanisms were introduced into yield function as internal variables of material degradation process.The evolution laws of the two damage parameters were given in rate-form.The damage constitutive model was implemented into the commercial codes ABAQUS via user defined material subroutines and applied to simulate the ductile fracture of the pre-cracked metal diaphragm to acquire the exact bursting pressure.The process of crack initiation,propagation and final fracture in the diaphragm was also reasonably predicted by the element removal procedure of ABAQUS/Explicit.The comparison with the experimental results shows that the proposed model can accurately simulate the fracture pressure and fracyure process of the notched diaphragm,and can be windely used to simulate the fracture process of ductile metals under tension shear mixed load mode.