Abstract
P-S-N curves is required because of the estimation of the probability expression of the tooth surface pitting of the gear. Failure data assumes that it is the Weibull distribution, and failure probability is asked by using regression analysis on weibull chart. However, generally failure data separates from an approximation straight line, existence of a minimum life is expected. So failure data assumes that it is the three parameter Weibull distribution, and the way forward to asking minimum life was examined. As the result, to apply regression analysis to data which separated from an approximation straight line was suitable.
