SUS304鋼の二段二重ひずみ振幅下低サイクル疲労 : ひずみ履歴依存形き裂伝ぱ則の導出と累積損傷評価

抄録

A small crack growth law-oriented approach was applied to explain the cumulative fatigue damage in a SUS 304 stainless steel which shows cyclic hardening behavior and the effect of prior fatigue damage on the subsequent crack growth rate in the case of two-step strain amplitude. After switching of strain, the stress amplitude and crack growth rate increased or decreased depending on the combination of the first and second strain amplitudes. These changes were interpreted as being induced by the effect of the prefatigue damage or strain history. A modified small crack growth law, compensating the discrepancy between the crack growth rates for constant and two-step strain amplitude, was proposed. Finally the modified crack growth law was found suitable for understanding the Miner rule in the case of materials which exhibit hardening behavior.