A study for the constitutive equation of carbon steel subjected to large strains, high temperatures and high strain rates

Abstract

In this paper, presented is a study for predicting the flow stress during hot deformation of carbon steel where the strain rate reaches as high as 3000 s −1 at high temperature (700–1100 °C). We have analyzed thoroughly Shida’s constitutive equation generally being used within the strain rate limit of 100 s −1 at elevated temperature. It was then assumed possible to obtain the constitutive equation which can depict the flow stress behavior of material beyond strain rate of 100 s −1 by modifying the Shida’s constitutive equation. The validity of the modified constitutive equation has been examined using split Hopkinson pressure bar (SHPB) experiment at high temperature. The high temperatures of SHPB test were obtained by enclosing the specimen in a clam-shell radiant-furnace. It has then been applied to hot rod rolling mill for predicting the surface temperature of workpiece where material throughout rolling experiences high strain rate (3000 s −1) and subsequently significant heat generation due to high strain rate plastic deformation. Results showed the modified constitutive equation could predict the flow stress value with a reasonable extent of error, in comparison with the one obtained from the SHPB experiment. The predicted surface temperatures of the workpiece during hot rod rolling were also in agreement with measured ones.