An experimental and theoretical investigation into the creep properties of a simple structure of 316 stainless steel

The paper describes a set of creep experiments conducted on 316 austenitic stainless steel in a coupled pair of uniaxial creep testing machines which simulate the performance of a two bar structure subjected to constant mechanical and cyclic thermal loading in the temperature range of 550–600°C. The experimental results are compared with theoretical predictions using a non-interactive viscous creep/plasticity model and a model which includes recovery effects. In addition, an upper bound solution based upon the “rapid cycle” creep solution is calculated. The comparison shows that the recovery model is in close agreement with experiment and that the rapid cycle solution can provide a simple conservative estimate of the average creep rate.Several of the tests specimens exhibited strain instabilities during the initial cycles of temperature when sudden increases in inelastic strain of up to 0.2% occurred. As the material had not shown such effects in standard isothermal constant stress tests, the effects of simultaneous variation of stress and temperature which occurred in the two bar tests seems to have contributed to the occurrence of these strain instabilities.