HOT DEFORMATION STUDIES ON A LOW-CARBON STEEL .2. AN ALGORITHM FOR THE FLOW-STRESS DETERMINATION UNDER VARYING PROCESS CONDITIONS

A variety of materials are processed using hot deformation, and simula tion of these processes needs information on the flow stress as influe nced by the process parameters since different locations in the work m aterial undergo a continuously changing temperature and strain rate co nditions. Based on the analysis of hot-deformation of a low carbon ste el under isothermal conditions, a methodology has been proposed for de termining the flow stress under continuously varying processing condit ions. The proposed methodology incorporates the strain rate and temper ature history effect,by taking into account the flow stresses resulted during the continuous deformation of the material. In this approach t he flow stress can be calculated from the sinh-Arrhenius constitutive equation, for which the constants are derived from the available isoth ermal compression test data obtained at mean constant strain rates. Th e methodology has been validated using the experimental data under var ying strain rate (between 0.1-10s(-1)) and temperature (between 900-11 00 degrees C) conditions. it has been found that the material behaviou r observed in constant strain rate tests as well as varying strain rat e/temperature tests (jump tests) can be adequately represented by the proposed methodology.