A technique for measuring the dynamic behavior of materials at high temperatures

A new experimental technique has been developed for the performance of high temperature, high-strain-rate experiments in the compression Kolsky bar (s plit-Hopkinson pressure bar or SHPB). The new technique (referred to as the High-Temperature Compression Kolsky Bar or HTCKB) uses an infra-red spot-h eater to rapidly heat the specimen to the desired temperature, and an elect ropneumatic actuation system to minimize the development of temperature gra dients in the sample. The technique is cheap and relatively easy to impleme nt and yet provides accurate, repeatable results. As an illustration of the application of the technique, we have examined the high-temperature respon se of the BCC metal vanadium at high-strain rates. Stress-strain curves are obtained for the material at strain rates of 4 x 10(3) s(-1) and at temper atures ranging from 300 to 1100 K (27-800 degrees C). Quasistatic (10(-3) s (-1)) experiments have also been performed on vanadium over a slightly smal ler range of temperatures, and the results are compared with the new high-t emperature, high-strain-rate data. It is observed that the rate of thermal softening is a function of the strain rate. These results illustrate the im portance of including the coupling between temperature and strain rate in t hermoviscoplastic constitutive models. (C) 1998 Published by Elsevier Scien ce Ltd. All rights reserved.