Characteristics of fatigue crack growth rates for ferritic steels in water environment provided by the ASME Code Section XI

ASME Code Section XIにおけるフェライト鋼の水質環境中における疲労亀裂進展速度評価の特徴

山口 義仁 ; 長谷川 邦夫; Negyesi, M.*

Yamaguchi, Yoshihito; Hasegawa, Kunio; Negyesi, M.*

Reference fatigue crack growth rates da/dN for ferritic steels in boiling water reactor environment are provided in Appendix Y of the ASME Code Section XI. Therein, da/dN are expressed as a function of stress intensity factor range K and as a function of the stress ratio parameter R. Different expressions apply for low K and high K. Current expressions result in lower fatigue crack growth rates in the water environment compared to the air environment for certain values of K. Therefore, the ASME Code states that reference fatigue crack growth rates in water environments are given by the expressions which results in higher fatigue crack growth rates. Sample calculations on fatigue crack growth under water and air environments were compared. The applicability of the current standard was confirmed.