变形模式对多孔金属材料SHPB实验结果的影响

利用两种改进后的Hopkinson杆实验分别测得多孔金属材料冲击端和支撑端的应力.实验结果及高速摄影表明,随着撞击速度的增加,试件两端的应力均匀性变差,分别对应着泡沫材料的3种变形模式:准静态模式、过渡模式、冲击模式.实验得出在冲击模式下,冲击端与支撑端的应力与试件的厚度无关,但是与试件的密度有关.在多孔金属的高应变率实验中,变形模式对SHPB实验有很大的影响,轴向惯性(波动)效应会导致试件两端的应力不均匀,此时利用SHPB得出的实验结果将会是应变率效应和惯性效应的耦合,不能真实反映材料的动态力学性能(应变率效应). 

INFLUENCE OF DEFORMATION MODES ON SHPB EXPERIMENTAL RESULTS OF CELLULAR METAL

Two types of improved Hopkinson bar were used to measure the stress on the impact and support ends of a cellular metal specimen.The experimental results and high-speed photography showed,as the impact velocity increased,the stress on the impact end increased,while the stress on the support end didn't change.The stress uniformity of two ends became worse when the impact velocity increased.Based on the experimental results we infer that under the shock mode,the stress on two ends is unrelated to the thickness of the specimen,but related to the density of the materials.In the high-strain-rate experiment of cellular metal,axial inertia (wave) effect will lead to stress non-uniformity.The results would be the coupling of axial inertia effect and strain rate effect and could not represent the dynamic mechanical properties of the materials.