Bending Fatigue Strength of Gears

Abstract

In this paper, the authors investigated the mechanisms of bending fatigue breakage of gears in one side and reverse loading conditions by examining the change in microstructure and in magnitude of residual stress with the number of load cycles and proposed Na-Np diagram, in which the number of load cycles after reverse Na is plotted against the number of load cycles before reverse Np, to indicate the bending fatigue properties of various gears such as annealed carbon steel gears, case-hardened gears etc. Moreover, the bending fatigue properties of shot-peened gears which had residual compressive stresses of considerable magnitude were investigated and it was made clear that there exists the optimum shot-peening conditions for the bending fatigue strength. The results obtained in this paper indicate some points which must be taken into consideration in the practical strength design of gears.