The determination of the pressure-viscosity coefficient of two traction oils using film thickness measurements

The pressure-viscosity coefficients of two commercial traction fluids are determined by fitting calculation results on accurate film thickness measurements, obtained at a wide range of speeds, and different temperatures. Film thickness values are calculated using a numerical method and approximation formulas from twelve models. It is concluded that, to assess the pressure-viscosity coefficient of these traction fluids, the Hamrock and Dowson approximation formula, and derivatives: Hamrock et al. and Chittenden et al., are the best choice, having an inaccuracy in between (-12%, +7%). These equations have been used far outsides the regime of the numerical data where they were based on.