@techreport{oai:jaxa.repo.nii.ac.jp:00044681,
 author = {下河, 利行 and 浜口, 泰正 and SHIMOKAWA, Toshiyuki and HAMAGUCHI, Yasumasa},
 month = {Oct},
 note = {When a new factor serving as an error in applied stress is added to an identical condition under which an S-N curve has been obtained, it causes a deviation from the fatigue life estimated from the S-N curve, and the amount of the deviation is related to the slope of the S-N curve. In the present paper, the accumulated effect of all factors causing the fatigue life scatter is regarded as an error in applied stress. The equivalent stress is defined as the sum of the applied stress and the error in applied stress. This concept is applied to the results of a series of fatigue tests on 2024-T4 aircraft structural aluminium alloy specimens with a circular hole at constant temperature and humidity. The interrelation between the scatter of the equivalent stress, the S-N curve, where N is the median fatigue life, and the scattering of fatigue life is discussed. The results obtained are compared with those in the case of specimens with a sharp notch(Kt=8.25) in a previous paper. The main results of this study are: (1) The fatigue crack initiation period of the specimen with a circular hole is about 2％ of fatigue life at the applied stress 26 kg/mm2. When an applied stress is lowered, it becomes longer. It is about 76％ of fatigue life at the applied stress 12.5 kg/mm2. (2)In the stress range where the shape and slope of the S-N curve are almost identical, the distribution shape and scatter of fatigue life obtained from the experiment are almost equal regardless of stress level and notch configulation. The gentler the slope of the S-N curve, the large the scatter of fatigue life becomes. (3)The equivalent stress is distributed almost in a normal distribution, and its standard deviation is nearly constant(0.270 to 0.377 kg/mm2) regardless of stress level and the ratio of crack initiation period to fatigue life. This result agrees well with that in the case of the specimens with a sharp notch(Kt=8.25). (4)The proposed equivalent stress distribution model, which has the normal distribution shape and a constant standard deviation regardless of stress level, gives a good explanation of the experimental fatigue life distributions within the interpolate region of the S-N curve drawn from the experimental results. (5)The distribution of fatigue life is dominated by the S-N curve. That is, the scatter of fatigue life is influenced significantly by the slope of the S-N curve around an applied stress. The distribution shape of fatigue life is derived from the S-N curve’s equation and the normal distribution of the equivalent stress. Therefore, in the stress range where the S-N curve on a semi-logarithmic seale is nearly straight, the fatigue life is distributed in a Log-normal distribution., 資料番号: NALTR0431000, レポート番号: NAL TR-431},
 title = {航空機用アルミニウム合金2024-T4円孔切欠き材における疲れ寿命のばらつきとS-N曲線との関係(温度および湿度を一定にした実験室内における実験)},
 year = {1975}
}