Friction Model Using Full Elastohydrodynamic Lubrication for Spiral Bevel Gears

Elastohydrodynamic lubrication phenomenon in spiral bevel gears was modeled in this study. The coefficient of friction calculated from the elastohydrodynamic (EHL) lubrication model is time varying. Friction is expected to have a greater impact on the spiral bevel gears than on any other right angled geared system due to the reversal of the contact area over a full tooth-to-tooth engagement cycle. The coefficient of friction formulated from an EHL model of spiral bevel gears depends upon lubricant properties, mesh forces and rotational speeds of the pinion and gear. Hence in this present study, a full elastohydrodynamic lubrication model was used to calculate the coefficient of friction in spiral bevel gears. The geometric and kinematic input data required for the EHL simulations were obtained from tooth contact analysis. Full numerical elastohydrodynamic lubrication simulations were carried out using the asymmetric integrated control volume (AICV) algorithm to compute the contact pressures and the coefficient of friction. The elastic deformations on the gear contact surfaces were calculated by circular convolution using a Fourier transform technique. The computed pressures, film thickness and the effective viscosity were used to calculate the time varying coefficient of friction for the spiral bevel gears. Parametric studies were conducted by varying the speed, torque applied, lubricant properties, temperature and slide to roll ratio to identify their impact on the time varying coefficient of friction.