Fatigue Life Behavior of a Hypoid Gear Tooth Root Taking the Influences of Orbital Forging into Account

This paper is concerned with the evaluation of the fatigue life and fracture mechanisms of a hypoid gear tooth root. The common milling manufacturing method for hypoid gear wheels is compared to the potentials of the innovative manufacturing method orbital forging. Extensive material and geometry analysis are performed and the local fatigue strength of the case hardened steel 18CrNiMo7-6 used in serial production is compared to the orbital forged and case hardened JIS steel SCM420H. Therefore a unique single contact engagement test procedure for hypoid gear wheels has been developed. The present investigations indicate a high potential for using orbital forging in the serial production. However, for an expected significant increase of the tooth root load carrying capacity due to the positive effects of forging (e.g. compressive residual stress, fiber orientation) and reaching the required geometry accuracy the process orbital forging has to be optimized in further steps.