NEW METHOD FOR DETERMINING SINH CONSTITUTIVE CONSTANTS FOR HIGH-TEMPERATURE DEFORMATION OF 300 AUSTENITIC STEELS

The constitutive equation relating peak stress sigma(p), strain rate epsilon (epsilon0 = 1 s-1) and temperature T for hot working: sigma(p) = (1/alpha) sinh-1 {(epsilon/epsilon0) exp[Q/R(1/T - 1/T')]}1/n, was re-examined to develop a new algorithm for determining the material constants alpha, n, Q and T'. By graphical or numerical techniques, T', n and Q are determined in a manner which re-checks the suitability of the equation and of the value of alpha which must be initially estimated or taken from the literature. The values for data on 301, 304 and 317 steels were derived by the two techniques and tested by calculating the stresses for each experimental condition. Comparison is made with previously derived constants, agreement to within about 5% being shown. The wide utility of the sinh equation is discussed.