Impact of Tooth Surface Pitting and Friction on Load Transfer and Static Transmission Error in Spur Gears

This study investigates the combined influence of tooth surface pitting and friction on the static performance characteristics of involute spur gear pairs. A numerical framework based on linear elastic static analysis is employed to evaluate gear meshing behavior for both undamaged and damaged teeth. Localized surface damage is represented using parabolic pit profiles introduced at multiple locations along the line of action, with three pit depths considered to simulate increasing damage severity. In addition, the coefficient of friction varies from zero to 0.30 in increments of 0.05 to examine frictional effects under a wide range of operating conditions.

The combined effects of surface damage and friction are quantified through key static performance metrics, including static transmission error (STE), tooth load distribution, tooth root stress, contact stress, gear moment, and bearing force. Results indicate that STE variation increases monotonically with both pit depth and coefficient of friction, with the most pronounced effects occurring when damage is located near the pitch point. Surface pitting causes localized reductions in tooth load and contact stress, while adjacent teeth compensate to maintain torque equilibrium. Friction further amplifies variations in STE, root stress, gear moment, and bearing force. The findings highlight the strong coupling between surface damage geometry and frictional effects, underscoring the importance of accounting for both factors when assessing the performance of spur gear transmissions.