Numerical analyses of elastohydrodynamically lubricated line and point contacts with rough surfaces by using semi-system and multigrid methods. (Volumes I and II)

Surface topography has long been recognized to have a significant influence on lubricated contacts. This thesis deals with the subject of elastohydrodynamic lubricated line and point contacts with rough surfaces (rough EHL contacts). As an introduction to this subject, a brief historical review is provided, followed by the mathematical descriptions of the rough EHL contacts for both Newtonain and non-Newtonain lubricants. On the basis of the merits of presently used numerical algorithms, two numerical methods, the semi-system method, and the multigrid method, were adopted for developing fast numerical solvers to simulate the rough EHL contact problems.;For line contact geometry, numerical simulations were performed for both steady and transient conditions. The surface irregularities examined range from single transverse bump or groove to random surface roughness. Based on the simulation results, an empirical formula for pressure fluctuations was regressed, and a fast pressure calculation model for EHL contact with arbitrary surface profiles was developed. As an extension to the 2-D surface irregularities, the problems of 3-D surface irregularities in line contact geometry were also examined.;Parallel simulations were performed for point contact geometry. The types of surface irregularities studied included single asperity, dent, bump, multiple asperities, waveiness, and random surface roughness. The orientation of the surface irregularities varies from transverse to striated to longitudinal.;The simulation results reveal the fundamental fact that under heavily loaded conditions the domination of pressure flow yields to the uni-directional shear flow in the EHL conjunction. Lubricant passes though the EHL conjunction at approximately the rolling speed. For sliding contact with moving surface roughness, the rolling speed transport behavior leads to an induced transient image. This transient phenomena will be fully developed under steady-state conditions; and, as a result, uniform film thickness in rolling and sliding direction is expected to form.;The thesis is completed with general conclusions and recommendations for future research work.