材料期刊网

通过将改进的X-W延性金属断裂模型结合修正的von-Mises准则嵌入ABAQUS/explicit用户材料子程序VUMAT的方式，对一系列铝合金2A12-T4试件的渐进断裂过程进行数值模拟，该模型以连续损伤力学为基础，并考虑静水压力和 Lode 角对损伤变量的作用。为了预测该模型的有效性并预测金属的延性断裂，对铝合金2A12-T4光滑圆棒、带缺口的棒材和紧凑拉伸试件(CT试件)进行单向拉伸试验及数值模拟。同时对比分析几何非线性和屈服准则的影响在数值仿真计算中的差异。结果表明，该断裂模型结合修正的von-Mises屈服准则可很好地预测2A12-T4试件渐进破坏试验的载荷-位移曲线及各试件的宏观断裂形貌。其中，“隧道”效应能够很好地解释CT试件处于平面应变状态的中心层和平面应力状态的表面层的抗断裂能力的差异。

A modified X-W ductile fracture model with modified von-Mises yield criterion based on the continuum damage mechanics which combined the effect of pressure and Lode angle on damage variable was implemented into ABAQUS/explicit through the user subroutine VUMAT to simulate the progressive failure of specimens of aluminum alloy 2A12-T4. In order to verify the modified fracture model and predict the progressive failure behavior of the ductile metals, a series of experiments of aluminum alloy 2A12-T4 specimens including smooth and notched round bars and compact tension (CT) specimen as well as corresponding numerical performances were conducted. Meanwhile, different numerical simulations with or without geometric non-linearity and different yield criteria were studied by comparing the difference. The numerical results show that the fracture model with modified von-Mises yield criterion can accurately and effectively predict the experimental results of 2A12-T4 specimens including load-displacement curves and macroscopic fracture morphology. Among them, the“tunnel”effect appearing in CT specimen can directly explain the difference of the fracture resistance between in plane stress layer and in plane strain layer.