高导无氧铜杆高应变率拉伸下的颈缩与断裂

采用Hopkinson拉伸实验装置和一种高速拉伸断裂实验新装置,对高导无氧铜(OFHC)杆件进行了一系列高应变率拉伸断裂试验.实验结果表明,局部化的断裂应变随拉伸速度增大并不明显增大,其断裂位置有随机性.存在一种临界拉伸速度,当冲击拉伸速度大于此值时,断裂即发生在冲击拉伸端附近,杆的其它部分几乎无应变.采用典型的Johnson-Cook本构关系,使用LS-DYNA程序进行一系列数值模拟,提出颈缩处直径收缩率达极值的颈缩失效判据,由此计算所得的局部化颈缩应变及断裂位置与试验回收结果有一定差别.

Necking and Fracture of Oxygen-Free high Conductive Copper Bars Subjected to high Strain Rate Tension

A series of tests for Oxygen-free high conductive (OFHC) copper bars subjected to high strain rate tension are carried out on the Hopkinson bar in tension mode and a novel facility based on a single gas gun system. The increase of the experimental localized fracture strains of specimens with the increase of the tensile velocity is not obvious, the fracture positions of testing bars are somewhat random. However, there exists a critical velocity, beyond which fracture appears near the impacted end of the bar, and the remainder of the bar is essentially free of plastic deformation. The numerical simulations of the experiments are performed by use of the typical Johnson-Cook constitutive relation in LS-DYNA. A criterion for necking and failure of bars based on the variation rate of the cross section of the specimen is presented and used in the numerical simulations. There are some differences between the computed positions of necking and localized necking strains and the experimental results.