Abstract
It is the big problem to evaluate the fatigue limit σ_<w1>, in order to safely design structures and machines. Under the condition of the fatigue crack initiation limit σ_<w1>, the present author defined the initial crack scale √<area> using the characteristic elastic field of the notch, the half length of the fatigue crack a and a notch depth t. Using this √<area>, the methods of calculating ΔK_<th> and σ_<w1> were proposed. In addition to it, in this condition it is made sure that ΔK_<th> exists on the band from ΔK_<th> prediction line of the micro fatigue crack within 18% error. Using ΔK_<th> calculated the prediction line and the value of √<area>, this evaluating method of σ_<w1> was confirmed with annealed 0.35% carbon steel. As a result, it was confirmed that this method to evaluate σ_<w1> is within 18% error. Moreover it was also confirmed that the fatigue limit σ_<w1> value by this prediction method is within 12% error.
