Estimates of Creep-Fatigue Interaction in Irradiated and Unirradiated Austenitic Stainless Steels

Abstract

Comparing data obtained from tests conducted on unirradiated Type 316 stainless steel in either the solution annealed or solution annealed and aged condition showed that aging was beneficial in improving both the fatigue and creep-fatigue properties at 593°C (1100°F). An indication was found that unirradiated Type 304 stainless steel would be more suitable for applications involving creep-fatigue interaction than unirradiated Type 316 stainless steel. Irradiation to fluences of 0.17 to 6.1 × 10²¹ n/cm² E > 0.1 MeV (450°C), resulted in a pronounced effect on the creep-fatigue resistance of these materials when tested at a strain range of 1%.

Both fatigue and creep damage values were calculated using actual times and cycles to failure and design times and cycles to failure. These damage values were summed linearly. Damage sums obtained were not found to be a unique value but dependent upon strain range, length of tensile hold time, and material condition.

Comparisons between estimates of irradiated fatigue behavior and actual irradiated fatigue lifetimes were made using limited data available. Estimates made using irradiated tensile data were usually found to be conservative in predicting pure fatigue behavior.