金属材料动态断裂试验接触状态研究

在标准冲击试样静态三点弯曲试验中，试样与支座之间保持接触，自始至终为三点受力状态。但在运用Hopkinson压杆进行动态试验条件下，由于加载速率较高，试样可能弹离支座，出现脱离现象。因此，试样有可能偏离三点弯曲状态。目前对试样与支座脱离接触的现象与规律的认识尚不统一。通过在支座上粘贴半导体应变片的方法，监测试样与支座开始受力时刻。比较发现，试样在受载瞬间并非处于三点受力状态，确实存在与支座间的脱离现象，并由试验得出不同跨距条件下发生脱离的临界条件。

Research on the contact state in the test of dynamic fracture of metal materials

In the test of three-point bending in the condition of standardized ballistic sample keep state the sample and abutment contact with each other and three-point endures stength all the time. In contrast, when we do the dynamic test with Hopkinson, the sample will flick from the abutment. The phenomenon of separation will happen because the loading speed is too rapid. The sample may drift off the state of three-point bending. Now owing to the phenomenon and rule which the sample deviate from the abutment, we still can not make a clear recognition. From this context, we try to paste the semiconductor strain gauges under the abutment, then monitor the time which abutment and sample endures strength at the moment of the beginning. After comparing, we observe that the sample is not in the condition of three point bending and the phenomeon of departing from the abutment is true. We can obtain the critical condition in which the separation takes place through different spans.