A Parametric Study on the Sub-Surface Stresses in Spur Gears under Mixed-lubrication Regime using Load-Sharing and Finite Element Simulation

Gears as key elements in power transmission systems are widely used in industry. Based on the manufacturing process, the surface of gears compared to other mechanical components such as roller bearings might be rougher and thus the effect of surface roughness in their performance should be given full consideration. One of the most important parameters in the gears' performance is the maximum shear stress that occurs below the surface, which is believed to be the key factor in surface fatigue and pitting. In this research, a model that employs the load-sharing concept to predict the friction coefficient and film thickness for each point along the line of action is developed. The sub-surface stress field that is generated below the tooth surface is calculated based on the friction coefficient. The predicted sub-surface stresses are compared to the results obtained from the commercial finite element software ABAQUS. An acceptable agreement is observed in comparing the results from the two methods. Finally, a parametric study has been conducted to study the effect of load, velocity, viscosity and surface hardness on the calculated maximum sub-surface shear stress and its location.