The performed investigation is a continuation of the work performed in SSM 2015:38 where fatigue tests were performed on pressurized welded austenitic stainless steel piping components. The specimens were subjected to a realistic variable amplitude loading with mainly reversed bending deformation and particular focus on high cycle fatigue. The previous fatigue results were quite dependent on the estimation of the stress concentration factor of the weld. Therefore, it was decided to continue this research by performing fatigue tests on pressurized non-welded austenitic stainless steel piping components.
The present study is aimed to investigate the margins of the ASME design curve for austenitic stainless steel, by performing fatigue experiments on a realistic non-welded austenitic stainless steel piping component and compare the results with the previous study where fatigue experiments on welded austenitic stainless steel piping components were performed. In this way, a more realistic analysis can be made of the fatigue strength reduction factor (FSRF). Another objective has been to improve the knowledge on the transferability for a non-welded piping component subjected to variable amplitude loading by comparing with smooth specimen data obtained with constant amplitude fatigue testing.
Extensive conservatism in the ASME approach to deal with transferability was confirmed. For the considered welded piping, the ASME design curve corresponded to a reduction in allowable number of cycles with a factor of at least 2.3. For the welded piping component, the fatigue strength reduction factor FSRF was estimated to 1.8 by comparing the results from the welded and unwelded pipe experiments.
The work has increased the understanding of the ASME margins and has improved the knowledge on fatigue in austenitic stainless steel components and the fundamental issue of transferability.