抄録
The Port method regarding the fatigue test of metals has pecently been appraised by many investigators. According to these results, n in Eq. 1 in this paper takes different values for different materials and no systematic arrangement has been established yet for each kind of material. Even if the numerical values of n are selected so that the experimental points may be located on a straight line, the extension of such line in most cases, deviates from a point equivallent to the Wöhler endurance limit on the abscissa. The author tried to obtain the equation of the S-N curve and the S-α curve for progressive load fatigue making use of the general idea of cumulative damage, and got the results which would explain the above experimental data and clarify the relations between the S-N curve and the S-α curve. From the above results, it might be said that caution must be exercised in determining the Wöhler fatigue limit by using the S-α diagram, because the curve plotted in this diagram does not form a straight line for what value of n, but is expected to form a complex curve as expressed by Eq. 4 in this paper.
