EFFECT OF STRESS STATE TYPE ON DEFORMATION PROCESS OF AUSTENITIC STEEL UNDER THERMAL CYCLING CONDITIONS

Analysis of the deformation process of an austenitic steel under the conditions of cyclic temperature variation has been made. The experiments were carried out on thin-walled tubular specimens loaded with axial force and torsional moment with the stress intensity kept constant and subjected to thermal cycling. The computed mean values of steady strain rate components, when compared with those obtained experimentally, showed that flow theory was in fairly good agreement with the experiment. Values of the exponent as well as the coefficient in the Norton-Bailey law depend however on stress state type. It was probably caused by interaction of two different failure mechanisms occurring under plane stress state conditions. It was also found that a type of criterion used for limit state description depends on stress intensity value.