Development of scaling parameter S for negative stress ratios R based on trend in experimental data for fatigue crack growth rates of austenitic stainless steels for ASME code Section XI

Negyesi, M.*; Yamaguchi, Yoshihito ; Hasegawa, Kunio; Lacroix, V.*; Morley, A.*

Fatigue crack growth rates for stainless steels in air environment are provided by the ASME Code Section XI. When the stress ratio R is positive from 0 to 1, the scaling parameter SR increases with the increasing ratio R, and the crack growth rates increase with the increasing stress ratio R. When R is less than 0, the parameter SR=1. Hence, fatigue crack growth rates under negative R ratios are independent of stress ratios R according to the ASME Code Section XI. However, from the literature survey, experimental data reveal that the fatigue crack growth rates decreases with decreasing R ratios below zero. The objective of this paper is to assess fatigue crack growth rates under such negative stress ratios for stainless steels in air environment. An equation determined from trends in experimental data surveyed in this study is proposed for negative stress R ratios to calculate the parameter SR for the ASME Code Section XI.