预置圆孔膨胀环动态断裂行为研究

On the Expanding Ring Dynamic Fracture Behavior with a Preset Circular Hole

利用中心线起爆膨胀环加载技术,采用分幅摄影技术观测了20号钢圆环在准一维拉伸作用下,预置圆孔缺陷临近区域的动态断裂特征。获得了高应变率下圆孔的变形、裂纹的萌生及扩展过程。并采用LS-DYNA3D有限元程序分步建模,将驱动器对膨胀环的冲击压力简化为直接作用于圆环内壁的压力历史,以此模拟了整个断裂过程。通过实验图像,得到裂纹尖端的位移以及速度随时间变化的曲线。结果表明,宏观可见裂纹出现于应力集中最大处,裂纹扩展速度随时间振荡,数值模拟与实验结果吻合较好。

Under quasi one-dimension tensile loading, dynamic fracture characteristics round the defect area of a 20# steel expanding ring with a preset circular hole were observed by using framing photography based on the central initiation loading technique. Circular hole＇s deformation, crack initiation and crack propagation at high strain rate were obtained. The whole fracture process was numerically simulated by LS-DYNA 3D finite element program that could be divided into two separate steps. The shock pressure applied on the expanding ring by steel driver was simplified as the pressure history straightly loaded on the ring inner wall, based on which, the fracture process was simulated. Through experimental images, the curve describing crack tip displacement and its velocity versus time was obtained. Results show that the macro-cracks emerge round the hole due to the stress concentration and crack propagation velocity oscillates with time. Simulation results are in good agreement with experimental data.