抄録
The propagation behavior of fatigue cracks was investigated under various stress ratios using structural carbon steel (JIS-S45C) specimens with small surface pre-cracks. The threshold condition of crack extension from pre-cracks was given by a constant value of the effective stress intensity range which was equal to the threshold value for long cracks irrespective of the stress ratio. Cracks initiated from precracks were arrested under lower stress amplitudes because of the development of crack closure with crack growth. The cyclic resistance-curve-method was used to predict the fatigue thresholds of the precracked components. The predicted values of the fatigue limit for crack extension, the fatigue limit for fracture, and the length of non-propagating cracks agreed very well with the experimental results. The effect of the mean stress on the fatigue limit of smooth specimen was successfully predicted by the cyclic resistance-curve-method.
