An engineering approach on sliding friction in full-film, heavily loaded lubricated contacts

Various schemes to approximate the sliding friction coefficient in heavily loaded lubricated contacts with different rheologies are studied. Rather than using complex full numerical thermo-hydrodynamically lubricated solutions to calculate the friction coefficient, in this paper the emphasis is on rather simplified approaches which are suitable for providing the user with physical insight of the phenomenon and at the same time fulfilling the most advanced engineering applications. The simplification of the equation for the lubricant velocity distribution for an assumed Hertzian contact with a fixed parallel film thickness and different fluid rheologies leads to simple solutions with comparable results to the recently obtained (through full numerical simulations) friction master curves from Jacod. Point-by-point models with thermal effects are included using the simplified model for the oil and wall temperature calculation from Olver and Spikes. The results are compared with full numerical solutions from literature and good agreement is found. A one-dimensional scheme is extended to a two-dimensional model where the integration of the varying viscosity with pressure and temperature is included. The wall surface temperature calculation is then carried out using a fast Fourier transform convolution approach.