Case depth requirements in carburized gears

Abstract

Summary Spalling fatigue in carburized gears occurs when the applied alternating subsurface shear stress exceeds the fatigue strength of the material. An analytical procedure is introduced which calculates, from the applied load and gear data, the applied subsurface shear stress gradient at the point of contact of the mating teeth. The hardness gradient required to accomodate the applied load is then determined from the shear stress gradient by applying a torsional fatigue strength-hardness relationship and a suitable design safety factor.