软材料的霍普金森压杆测试新技术

A NEW TECHNIQUE FOR TESTING SOFT MATERIAL USING A MODIFIED HOPKINSON PRESSURE BAR

提出了一种用于软材料动态压缩性能测试的霍普金森压杆改进方案。该方案采用了长杆直接撞击试件的加载方式并在透射杆中使用半导体应变片。通过对测试过程中试件内应力波传播的分析,提出了实现软材料动态性能测试时试件内应力尽快均匀的最佳加载方式以及实现此种加载的加载整形技术。该方案能解决由于杆-试件之间波阻抗失配导致的应变信号微弱而测试困难的问题,与高聚物霍普金森压杆相比则具有更高的可靠性。该方案能实现对软材料的大变形、近似恒应变率及大应变率范围动态压缩测试。最后给出了一个试验性装置的测试结果。

This paper describes a modification of the split Hopkinson pressure bar for the dynamic compressive property testing of soft material. The specimen is directly struck by the projectile bar in this modification. Semiconductor gage is used to measure the strain signal in the output bar. The stress wave propagation in the specimen is analyzed and the required loading shape and a practical loading shaping technique for achieving stress uniformity in the specimen is presented. This modification can overcome the difficulty of weak strain signal measurement caused by the unmatched impedances of the bar and the specimen and is more reliable than polymer Hopkinson pressure bar. It can achieve a large deformation, a large range of testing strain-rate and an approximately constant strain-rate dynamic compression testing. An experimental device has been built and some test result is presented.