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

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.