MODELING OF AN AUSTENITIC STAINLESS-STEEL AT HIGH-TEMPERATURE UNDER IN-PHASE AND OUT-OF-PHASE CYCLIC TENSION-TORSION LOADING

Results are presented for experiments performed on austenitic stainles s steel type 316 L at a temperature of 600 degrees C. The tests were c arried out under both unidirectional (1D) and bidirectional (2D) cycli c tension-torsion loading, both in and out of phase and with one (in t he case of 2D ratcheting) or two cyclic components. For the 2D loading s, it is shown that a weak supplementary hardening Delta H+ appears th at is primarily a function of the phase difference Phi between the str ain components, and the ratio R between the maximum amplitudes of thes e components. These observations conform qualitatively with those alre ady reported for ambient temperatures; but quantitatively it is shown that the maximum amplitude of this supplementary hardening is a sharpl y decreasing function of the temperature. A simple phenomenological fo rmulation is proposed which, when integrated into a unified visoplasti c model, developed elsewhere, leads to a good representation of the ex perimental results under cyclic 1D and 2D loadings. The model describe s the effects due to the loading rate, the phase difference between th e two cyclic components, and the 2D tensile-torsion ratchet.