Quantitative Evaluation of Size Effect based on Statistical Behaviors of Fatigue Limit (Rotating Bending Fatigue Limit of S35C, SFA55--Steel and AC8A--AI Cast Alloy)

摘要

To investigate the "size effect" of rotating bending fatigue test are carried out on solid bar specimens with various gage lengths, that is, the length of the parallel part, and the same cross section of S35C steel, SFA55 steel and AC8A aluminum alloy. Statistical test of significance about the effect of gage length on fatigue limit was carried out by using the mean and the standard deviation of fatigue limits obtained by an up-and-down method. The result of the statistical tests show that a significant difference exists among fatigue limits of each gage length. Experimental values of the size effect are coincide with the calculated value by means of the assumption that strength of micro defect in material belongs to Weibull distribution. In the experimental results, shape factor: m of Weibull distribution is 30～80 and depends heavily on the material and metallurgi- cal structure.