高温低サイクル疲労における負荷保持時間の影響

概要

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The low-cycle fatigue tests were conducted at elevated-temperatures on two alloys, Type SUS 32 HP (equivalent to AISI 316) stainless steel and 1Cr-1/4 Mo steel, SCM 3, and the effect of holding time at the absolutely maximum tensile or compressive strain was investigated. A considerable reduction in their fatigue lives was observed when the test temperature was raised and the holding time was increased. The linear fraction rule between creep and fatigue damage was compared with the experimental results, ant it was found that there lie several serious problems in this rule, especially when applied to cyclic softening materials such as SCM 3 steel. The Endo's theory on corrosion-fatigue was modified to develop the following life-evaluating equation, which takes consideration for the relationships among the cycle-dependent effect by fatigue damage, the time-dependent effect by oxidation, and their combined effect. (1+B・t_0^<n_1>・n_f^<n_1>)・ε_<pR>・ N_f^<α_0>=C_0 where, T_0, ε_<pR>, and N_f are the holding time during a half cycle, the plastic strain range, and the number of cycles to failure, respectively, and B, n_1, n_2, α_0, and C_0 are constants. This equation was shown to represent the experimental results well. The time-dependent effect may be interpreted to include other supplementary effects such as creep damage and deterioration of materiels.
社団法人日本材料学会の論文
1973-03-15