Study on Gear Bending Fatigue Strength Design Based on Reliability Engineering : Reliability Estimation of Bending Fatigue Strength of Supercarburized Steel Gear

Abstract

Gear designing is traditionally based on the factor of safety, and the possibility of failure is quite often arbitrary. Fatigue failure is a random variable for which knowledge of the distribution functions of life and strength is essential in the estimation of bending fatigue failure and in reliability analysis. In this paper, to obtain the basic data for gear bending fatigue strength design, stationary bending fatigue testing of super-carburized steel gears with two different case depths was performed under a constant load range condition by using an electrohydraulic servo-controlled pulsating bending testing machine. The result obtained shows that the fatigue life distribution and the fatigue strength distribution are well represented by a three-parameter Weibull distribution. Reliabilities based on safety design criteria for constant stress and random stress fatigue are talculated from available fatigue data. The relationship between the deterministic central factor of safety and reliability is also discussed.