Tooth Mesh Characterization of Spur Gear Pairs with Surface Pitting Damage

A finite element/contact mechanics (FE/CM) method is used to determine the tooth contact forces, static transmission error, and tooth pair stiffnesses for spur gear pairs that have pitting damage. The pitting damage prevents portions of the tooth surface from carrying load, which results in meaningfully different contact pressure distribution on the gear teeth and deformations at the mesh. Pits of elliptical shape are investigated. Parametric analyses are used to investigate the effect of pit width (along the tooth face) and height (along the tooth profile) on the gear tooth mesh interface. Pitting damage increases static transmission error and decreases tooth pair stiffness. Tooth contact forces differ only in the portions of the mesh cycle when multiple pairs of teeth are in contact and share the transmitted load. Pitting damage does not change the loads when only a single pair of teeth are in contact. The duration of the mesh cycle where the static transmission error and tooth pair stiffnesses deviate from those for healthy teeth also increases with increasing damage area. Pitting damage originating at the pitch generally results in significant static transmission error and tooth pair stiffness variations from healthy when only a single pair of teeth are in contact. When the damage originates elsewhere on the tooth, large differences in these results occur in regions of the mesh cycle when multiple pairs of teeth carry the load. Accurate gear tooth contact analyses require more refined contact grids to accurately capture the steep contact pressure gradients near damage. The static transmission errors, mesh stiffnesses, and tooth contact forces determined in this work could be used to determine the damage-induced dynamic response from analytical gear models.