Statistical Models of Mean Stress and Water Environment Effects on the Fatigue Behavior of 304 Stainless Steel

Recent research efforts have focused on characterizing the effects of light water reactor environments on the fatigue behavior of austenitic stainless steels. In conjunction with these experimental programs, there has been a significant effort at Argonne National Laboratory to develop statistical models for predicting the fatigue behavior of austenitic stainless steels in air and water environments at prototypical temperatures and loading rates. Some recent testing has also been concerned with the effect of mean stress on the fatigue behavior of 304 stainless steel in air. The ultimate goal of all these efforts is to allow development of fatigue design curves and design procedures that will assure adequate margin to fatigue crack initiation under prototypical operating conditions. In this paper, a best-fit strain-life curve for 304 stainless steel in air that takes into account the effect of mean stress is developed using the Smith-Watson-Topper equivalent strain parameter. A model for predicting the effect of water environments on fatigue life in both low and high oxygen water environments for a range of temperatures and loading rates is also described. Additional effort is required to develop the most appropriate way to develop a fatigue design curve from the mean stress and water effects models