Understanding the anomalously long duration time of the transmitted pulse from a soft specimen in a kolsky bar experiment

The reason for the observation of an anomalously long pulse duration time of a signal transmitted from a soft specimen in a Kolsky bar experiment is investigated. A systematic numerical experiment based on explicit finite element analysis has been carried out using elastic specimens with varying elastic moduli. The soft specimen is in a compressive state even after the passage of the pulse because it cannot push the bars, such that a fairly long transmitted pulse is monitored at the gage position of the output bar. The arrival of the second pulse (tensile) from the right-end surface of the output bar releases the first transmitted signal (compressive) coming from the compressed state of the specimen, which puts an end to the fairly long transmitted pulse. Because the observation of a prolonged transmitted pulse is a natural phenomenon, the prolonged transmitted pulse should not annoy researchers in the process of confirming the validity of experiments on soft specimens. Our concern in verifying the validity of experiments can be limited to other aspects such as the process of measurement and the amplification of weak transmitted signals coming from soft specimens.