鋼材の歪制御低サイクル疲労強度推定に関する研究(第3報)

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In the study of low cycle fatigue behavior, Manson-Coffin's linear relationships have been well recognized. However, some experimental results reveal a new evidence which is a divergence from Manson-Coffin's linear relationship between plastic strain range and number of cycles to failure under strain controlled cycling condition. This phenomena is closely related to the strength level above about 60 Kg/mm^2 and micro structure which has bainitic structure. For these steels linear relationship between total strain range and number of cycles to failure is applicable. The data in this investigation clarify that the method of predicting the low cycle fatigue strength proposed by Manson gives risky results. Therefore, it is desirable to predict the low cycle fatigue strength according to the following formula. For steeels which satisfy Manson-Coffin's linear relationship : ε_tr=0.715ε_f^<0.705・N_f^<-(0.558nf+0.404)>+(2.91σ_u/E)N_f^<-{0.056+1.29/σu-26.3)}> For steels which show a divergence from Manson-Coffin's linear relationship : in the low cycle range ε_<tr>=1.39×10^<-4>σ_u+0.715ε_f^0.705)N_f^<-(1.08n_f+0.227)> in the intermediate and high cycle range ε_<tr>=1.39×10^<-4>σ_u・N_f^M1{0.056+1.29/(σ_u-26.8)}>
社団法人日本船舶海洋工学会の論文