Hot deformation studies on a low-carbon steel: part 2 - an algorithm for the flow stress determination under varying process conditions

Abstract

A variety of materials are processed using hot deformation, and simulation of these processes needs information on the flow stress as influenced by the process parameters since different locations in the work material undergo a continuously changing temperature and strain rate conditions. Based on the analysis of hot-deformation of a low carbon steel under isothermal conditions, a methodology has been proposed for determining the flow stress under continuously varying processing conditions. The proposed methodology incorporates the strain rate and temperature history effect, by taking into account the flow stresses resulted during the continuous deformation of the material. In this approach the flow stress can be calculated from the sinh-Arrhenius constitutive equation, for which the constants are derived from the available isothermal compression test data obtained at mean constant strain rates. The methodology has been validated using the experimental data under varying strain rate (between 0.1–10s −1) and temperature (between 900–1100°C) conditions. It has been found that the material behaviour observed in constant strain rate tests as well as varying strain rate/temperature tests (jump tests) can be adequately represented by the proposed methodology.