Study on Equivalence of Plastic Work at High Temperatures and Strain Rates (1st Report) −A Special Torsional Hopkinson-Bar Testing Machine and A Preliminary Experiment−

In metal machining operations, material is deformed at large strains, high temperatures and strain rates. The deformation mechanism has been analyzed by postulating the equivalence of plastic work or an effective strain-hardening relationship, which is based on Prandtl-Reuss’s flow rule and von Mises yield condition. In this paper in order to examine the validity of the hypothesis under the conditions of machining, a special torsional Hopkinson-bar testing machine is designed and constructed. A preliminary experiment shows that the torsional flow stress, which is transformed into compressive stress by using the hypothesis, does not necessarily coincide with the compressive data for 0.19％C carbon steel, when the effective strain exceeds around 0.4 at a temperature of 673 K and a strain rate of 1000 s^<-1>. The agreement can be seen up to larger strains at higher temperatures and/or lower strain rate deformations. The range of strains, which validates the hypothesis, decreases in the order aluminum alloy，0.19％C carbon steel, commercial zinc