Evaluation of creep-fatigue design methods by structural failure tests under thermal loads: stepped hollow cylinder model with a shoulder fillet

摘要

Creep-fatigue tests were conducted under cyclic thermal stresses for simple structural model (stepped hollow cylinder model with a shoulder fillet) made of modified 316 stainless steel (316FR). The specimens had longitudinal butt welded joints byGTAW. Failure life was defined as the cycle at which small visible cracks were detected. The experimental results were compared with predictions based on elastic analysis and inelastic analysis.The comparison between experimental and predicted results showed that (1) Life estimations based on inelastic analyses gave good agreement with the crack initiation lives in the structural model tests, where the signs of axial and hoop strains are thesame(in-phase) or uniaxial strain condition, and (2) Predictions by the Japanese FER Design Guide based on elastic analysis gave conservative results. The accuracy of estimation could be improved if the elastic follow-up factor evaluated by inelasticanalysis was used, instead of the default value, 3 given in the Guide.