Flow stress equation with effect of strain-rate and temperature histories under processing

The effects of strain, strain-rate, temperature on the now stress variation of some metals are experimentally discussed by using the modified Hopkinson bar type impact testing machine. It is found through the test that now stress is greatly affected by both histories of temperature and strain rate. In order to obtain a now stress including the both effects under deformation, a reference stress is proposed. The reference stress is defined as the yield stress under the reference condition. The reference stress is defined by only generalized deformation energy, which is accumulated by plastic deformation and annihilated by annealing. The new practically useful now-stress equation is proposed, in which the reference sti ess, strain-rate and temperature but total strain are included. The proposed now-stress equation is applied to deformation process with varying condition and compared with experimental results.