応力制御下における任意のき裂を有する金属の疲労限度の定量的評価 : 第1報,応力比が-1の場合

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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 H_B≃600 are reported. The threshold stress intensity factor range under a stress controlled condition, ？K_w, is introduced for the purpose of predicting the fatigue limit of a metal with an arbitrary crack. The ？K_w value of a long crack, ？K_wUL, is obtained from the fatigue crack propagation limit σ_w2 of specimens with a sharp and deep notch: ？K_w increases with crack length, and ？K_wUL is an upper limit of ？K_w. Since there are few σ_w2 data of steels with H_B≥400, the σ_w2 values are evaluated by the fatigue crack initiation limit predicted using Linear Notch Mechanics and the relation between σ_w1 and σ_w2 at the branch point. Using ？K_wUL values of many metals with a long crack, the ？K_wUL values are approximated with a simple formula. Moreover the lower limit value of ？K_w versus the crack length, ？K_wLL, is proposed. Then using the ？K_w and ？K_wUL formulae and the ？K_wLL value, the smallness of a fatigue crack is clarified.
社団法人日本機械学会の論文
2002-09-25