On the Expanding Ring Dynamic Fracture Behavior with a Preset Circular Hole
预置圆孔膨胀环动态断裂行为研究

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.