基于试验与模拟的修正GTN模型参数反求分析

Parameter Identification of Enhanced GTN Model Through Experiments and Simulation

设计6种不同应力三轴度的试样,进行拉伸试验并得到不同工况下的载荷-位移曲线.运用Voce+Voce流动应力模型外推拉伸试验数据得到材料的力学性能曲线.运用有限元软件ABAQUS/Explicit模块及用户子程序VUMAT将Nahshon提出的含剪切修正项的GTN(Gurson-Tvergaard-Needlemen)模型应用到有限元模拟中,研究各组试样的损伤演化和断裂过程.为使GTN模型更准确地应用到不同应力状态下,假定损伤参数εn为关于应力三轴度η的指数函数.运用反求法分析不同缺口半径的拉伸试验,确定GTN模型中面向高应力三轴度情况的损伤参数,同时结合数值模拟与剪切试验的对比确定剪切系数Kw.结果表明,确定的修正GTN模型参数可以应用到较宽的应力三轴度范围包括纯剪状态.

Six specimens at different stress triaxialities were designed in this study forcedisplacement curves under different wor property curve was obtained by extrapolating king the conditions were obtained. The ideal The corresponding material mechanical results from smooth round bar tension test via the Voce ＋Voce flow stress model. The enhanced GTN （Gurson-Tvergaard-Needlemen） damage model proposed by Nahshon was implemented into the ABAQUS/Explicit code through VUMAT subroutine to simulate the damage evolution and fracture process of each test. The damage parameter εn was assumed to depend on the stress triaxiality in the form of an exponential function. The damage parameters wGurson-Tvergaard- Needlemenere were calibrated through the notched bar tensile tests using the inverse approach. The shear coefficient Kw was determined by comparing the results of pure shear test experiment and simulation. The results show that the enhanced GTN model with these identified parameters can be applied into a widely range of stress triaxiality including pure shear stress state.