Effect of nonlinear shear velocity distribution on load carrying capacity of pad bearings

The work aims to study the effect of nonlinear shear velocity distribution on load carrying capacity of pad bearings for mechanical devices such as sliding bearings in conformal contact. The velocity distribution of lubricating oil film was measured by fluorescence bleaching recovery method combined with the oil film measurement system. The theoretical analysis of the bearing capacity of hydrodynamic lubrication in conformal contact was carried out by the generalized Reynolds equation combined with the shear velocity distribution. Due to apparent slip or low viscosity layer, PAO8 and PB450 in micro-nano gap presented nonlinear velocity distribution when film thickness was small, and the degree of non-linearity changed with the film thickness. The viscosity of lubricant along the film thickness was not a constant, showing linear distribution at high thickness. The sigmoid function was used to fit the nonlinear velocity distribution. The nonlinear velocity profile made the viscosity parameter 1/ηeff greater than 1 in the generalized Reynolds equation. With the increase of the non-linearity degree, the viscosity parameter increased rapidly and then slowly. The corresponding convergence ratio of the maximum dimensionless bearing capacity was larger than that of the classical calculation value 1.2. When the film thickness was higher, there was a linear velocity distribution, and the corresponding convergence ratio of the theoretical maximum bearing capacity was 1.2. Compared with the experimental results of dimensionless bearing capacity-convergence ratio curves obtained by optical interferometry, there was a good consistency between theoretical and experimental results. Therefore, the shear velocity distribution can be used to predict the hydrodynamic lubrication characteristics of mechanical devices. © 2020, Chongqing Wujiu Periodicals Press. All rights reserved.