Stress Uniformization Process in Specimens during Compression Process with Split Hopkinson Pressure Bar System

In split Hopkinson pressure bar(SHPB) test,the stress uniformization process in specimens was studied.The results indicate that the stress non-uniformity obviously appeared at the beginning of dynamic compression,which mainly behaved as follows: the level of stress was different at the two bottoms of the specimen and the tenor of stress-time was non-synchronizing along with large vibration.In the course of time,the stress distribution in the specimen gradually got uniformed.The non-uniformity degree of stress distribution in the specimen was judged by absolute stress unevenness α(t).The curve of α(t)-t had an obvious kinkpoint M.It is suggested that the correspondent time of kinkpoint M is the time needed for stress distribution uniformization in the specimen.