Study on mixed elastohydrodynamic lubrication performance of point contact with non‐Gaussian rough surface

Abstract

A numerical method is proposed to evaluate the effect of non‐Gaussian roughness on point contact elastohydrodynamic lubrication (EHL). A mixed EHL model of point contact, considering non‐Gaussian roughness, is developed. The oil film pressure in the model was controlled by the Reynolds equation of average flow, and the contact pressure of asperity was obtained by the rough surface micro‐contact model. The influence of non‐Gaussian roughness parameters on contact pressure distribution, film thickness profile and the ratio of asperity pressure to contact load (asperity load ratio) are investigated based on the mixed EHL model. The results show that the asperity pressure increases as root mean square (RMS) roughness increases, skewness and kurtosis. The film thickness also increases with RMS roughness and skewness, but is not sensitive to kurtosis.

The Influence of Non-Gaussian Roughness and Spectral Properties on Mixed Lubrication for Heavily Loaded Counterformal Contacts

“…Table 3 shows the dimensionless input parameters used throughout the present study. The grid points (257 × 257) and dimensionless domain lengths (−4 to 2 in the X direction and −3 to 3 in the Y direction) are adopted from a recently published work [28]. The Hertzian parameters for the point contact configuration are defined in Appendix C. The asperity load ratio calculated from the present simulation is compared with published results to verify the accuracy of the developed mixed lubrication model.…”

“…where µ 0 is the viscosity at ambient conditions; ρ 0 is the density at ambient conditions; and Z R is the viscosity-pressure index, which was assumed to 0.68 [28].…”

“…It is well known that real engineered rough surfaces produced by conventional machining processes exhibit non-Gaussianity in roughness heights [27]. Therefore, non-Gaussian effects are of utmost importance to consider in the average Reynolds equation and also in the asperity contact models for an accurate prediction of mixed lubrication parameters as well as the coefficient of friction [28]. When it comes to the research related to the non-Gaussian roughness effect on mixed lubrication, particularly for non-conformal (point or line) contacts, fewer attempts have been made earlier.…”

“…Pei et al [27] developed formulas for calculating the asperity load ratio and film thickness (minimum and central) considering the non-Gaussian roughness (skewness and kurtosis). Guo et al [28] employed a PC average flow model to study the non-Gaussian roughness effect on film thickness and asperity load ratio for non-conformal point contacts. Three different types of frequency curves using the Johnson translator system were used to obtain the Probability Density Function (PDF) of asperity heights with non-Gaussianity [28].…”

“…Guo et al [28] employed a PC average flow model to study the non-Gaussian roughness effect on film thickness and asperity load ratio for non-conformal point contacts. Three different types of frequency curves using the Johnson translator system were used to obtain the Probability Density Function (PDF) of asperity heights with non-Gaussianity [28]. The non-Gaussian roughness was considered to predict the surface wear and roughness parameters during the running-in of line contacts under mixed lubrication [32].…”