Micropitting Load Capacity of Spur and Helical Gears

Abstract

In this chapter, a general survey is first done on the micropitting damage of spur and helical gears, which manifests itself to the roughness scale. The mechanism that trigger this type of damage as well as the characteristics that distinguish it from those typical of macropitting (the classical pitting) are described. The problem to be solved for a reliable calculation procedure of micropitting load carrying capacity of gears are then analyzed and, to this end, the ideal characteristics of a general micropitting model are described. An interesting tribological-dynamic analytical model for cylindrical spur gears is then described, which also consists of a three-dimensional analytical-numerical contact sub-model and a multiaxial fatigue sub-model. The procedure for calculating the surface durability of spur and helical gears in accordance with the ISO standards is described, highlighting when deemed necessary how the formulae used by the same ISO are anchored to the theoretical bases previously discussed. Finally, for a better understanding of micropitting mechanisms, attention is drawn to the need to introduce, instead of traditional profile parameters, the areal field parameters that best describe the topography and texture of surfaces.