実働応力疲労に及ぼす負荷条件の影響と推定寿命 : 疲労限度以上の応力を少数回含む場合

概要

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The fatigue life under repetition of varying stress is variable according to the difference of the given load spectrum. In order to find what factor is most effective to the fatigue life, program fatigue tests by rotating beam including a few cycles of over stresses were performed, and tentative comparison was made about several load spectrums. The test results are summarized as follows; (1) In program fatigue tests, four factors, the cumulative cycle ratio of over stresses in 1 block (Σ_*), stress level of the mode (σ_m), the width of varying stress range (σ_b), and the cycle ratio of maximum stress to the mode stress (n_1/n_<max>), are most effective to the fatigue life. (2) A parameter K was made from these factors, and several different tests were well linearized using K, and fatigue life is to be estimated approximately by this method. In the case of small value of K so short life as Σn/N=0.05 was found to be probable. Σn/N=K^<1/5.4>=[n_1/(n_<max>)・σ_w^2/(σ_b・(σ_w-σ_m))]_<1/5.4> σ_w: stands for the fatigue limit by constant stress amplitude. (3) But, even if such small value is expected, it is allowable to use Mine's hypothesis by modifying the original S-N curve to 70 per cent of stress at knee point.
社団法人日本材料学会の論文
1968-02-15