K-0524 湿度に依存する高強度鋼の2段折れ曲がりS-N特性(S04-3 高強度鋼の超高サイクル疲労(2))(S04 金属材料の組織と疲労強度信頼性)

概要

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Cantilever-type rotary bending fatigue tests were performed on SNCM439 in laboratory air and dry air and on SUJ2 in controlled humidity in order to study the effect of humidity on the fatigue behavior in high strength steels. It was found that humidity exerted a significant influence on the S-N characteristics in both steels. SNCM439 had step-wise S-N curves in both environments, but the transition stress at which crack initiation changed from surface to subsurface was lower in laboratory air than in dry air. Step-wise S-N curves were also seen in SUJ2 in relatively lower humidity up to 55% and the transition stress decreased as humidity increased. In high humidity and water environments, cracks were always generated at the surface, thus leading to the disappearance of step-wise S-N curve.
2001-08-22