冲击载荷下镁铝合金裂纹动态扩展过程的数值模拟

采用基于黏聚裂纹模型的扩展有限元方法，开展了镁铝合金结构冲击破坏过程的数值模拟研究。通过镁铝合金三点弯曲试样冲击实验，获得了不同子弹撞击速度下试样的冲击破坏模式。在此基础上，建立了实验结构的扩展有限元模型，并采用最大主应力准则，以及含损伤型的本构关系模拟材料的冲击断裂行为。对于裂纹尖端附近区域，采用黏聚裂纹模型模拟裂纹的断裂过程。对子弹速度分别为12.2、15.1、26.3 m/s的3种工况下镁铝合金试样的动态破坏过程进行了数值模拟研究，获得了与实验相一致的断裂模式。计算结果表明，试样以Ⅰ型断裂模式为主，裂纹沿初始预制裂纹方向扩展。当裂纹扩展到一定程度后，在试样韧带区域被撞击端附近，由于应力波及边界效应导致该区域处于复杂应力状态，试样出现复合型断裂模式，裂纹偏离原扩展路径，与本文实验结果相吻合。

Numerical research on dynamic fracture process of magnalium alloy under impact load

The impact fracture process of the magnalium alloy structure was investigated using the XFEM-based cohesive model. First, by the numerical modeling carried out in abaqus software based on XFEM, the fracture mode of magnalium alloy specimens at different bullet impact velocities were obtained from doing a three-point bending experiment. After this, the impact fracture process of experimental model under three different loads at respectively three bullet impact velocities of 12.2, 15.1 and 26.3 m/s was simulated using the XFEM, and the alloy's failure pattern was obtained by performing numerical calculation, the results from which are consistent with those obtained from the experimental. The simulation results show that Mode Ⅰ is the major fracture mode of the specimen, and the crack propagates mostly along the initial crack direction. The crack makes a turn at a point 3~4 mm from the impacted part of the specimen, where the fixed fracture mode is dominant. This agrees with both the experimental results presented in this paper and with the calculated results found in the related literature. Finally, the reason for the fixed fracture mode in the specimen was also analyzed in the paper.