In this paper, the result from rotating bending fatigue tests of notched specimens are carried out on aluminum cast alloys and high strength steels with HB ≃ 600 are reported. The threshold stress intensity factor range under a stress controlled condition, ΔKw, is introduced for the purpose of predicting the fatigue limit of a metal with an arbitrary crack. The ΔKw value of a long crack, ΔKwU L, is obtained from the fatigue crack propagation limit σW2 of specimens with a sharp and deep notch; ΔKw increases with crack length, and ΔKwU L is an upper limit of ΔKw, Since there are few σw2 data of steels with HB ≥ 400, the σw2 values are evaluated by the fatigue crack initiation limit predicted using Linear Notch Mechanics and the relation between σw1 and σw2 at the branch point. Using ΔKwU L values of many metals with a long crack, the ΔKWU L values are approximated with a simple formula. Moreover the lower limit value of ΔKwU L versus the crack length, ΔKwLL, is proposed. Then using the AKw and ΔKwUL formulae and the ΔKwLL value, the smallness of a fatigue crack is clarified.
|ジャーナル||International Journal of Fracture|
|出版ステータス||出版済み - 9 2004|
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