2009 Volume 58 Issue 2 Pages 143-148
This paper investigates the applicability of the procedure proposed by one of the authors for estimating the nonproportional loading effect on PP test lives to the estimation of the creep-fatigue lives of SUS304 austenitic stainless steel subjected to nonproportionally combined push-pull and cyclic torsion under CC type strain waveform. Fully reversed strain-controlled CC tests were conducted on thin-walled tubular specimens of SUS304 steel at 973K in air under in-phase and 90deg out-of-phase straining conditions. The partitioned inelastic strain range versus life equations, Δεcc versus Ncc relationships, obtained from three different proportional loading conditions, such as push-pull, cyclic torsion, and in-phase combined push-pull and cyclic torsion, are found to be correlated with one another by the multiaxiality factor. By using the multiaxiality modified Δεpp versus Npp and Δεcc versus Ncc relationships, the 90deg out-of-phase straining CC test lives were estimated by the proposed procedure, where the strain range partitioning was done by superposing the hysteresis loops of PP tests on those of CC tests. As the results, the estimated lives are found to agree well with the experimental lives in adopting the superposition method rather than the rapid loading method.
