| Elastohydrodynamic (EHD) lubrication is a lubrication process which usually occurs in concentrated load-supporting or load-transmitting contacts. Such contacts exist, for example, in rolling-element bearings, gears and cam-follower mechanisms. In EHD lubrication, the contact surfaces are not only separated by a thin lubricating film, but also elastically deformed to an amount comparable to the film thickness. The film thickness in an EHD contact can be as small as a fraction of a micron, and the contact pressure can be as high as several GPa. Film thickness and pressure are closely related to surface failures such as scuffing and fatigue, and are therefore the most important considerations in EHD lubrication.;Because EHD contacts are governed by a highly nonlinear system of integral and differential equations, numerical methods must be used to obtain a solution. However, solutions of EHD problems, especially those problems found in practice, are difficult to obtain due to numerical instability and computational intensity. In this thesis, an efficient, robust, multi-level computational algorithm is developed that can efficiently and accurately solve both steady-state and transient EHD line-contact problems. This algorithm is used to simulate processes of micro-EHD lubrication associated with surface irregularities. The surface kinematic conditions simulated are pure rolling and simple sliding with a moving or stationary surface irregularity. The simulation results correlate well with previous experimental measurements and observations. Three lubricant rheological models are also analyzed. The analysis reveals that the effects of lubricant rheology on the film thickness and pressure are very significant in micro-EHD lubrication.;The study also includes the formulation and use of an EHD lubrication model to analyze the kinematic and dynamic behavior of high-speed cylindrical roller bearings. Bearing stiffness, internal load distribution, running torque, and amount of roller skidding can be calculated under various operating conditions. Effects of manufacturing imperfections can also be analyzed in terms of outer-raceway waviness and roller diametral tolerance. The analysis program developed can be a useful tool in the design and evaluation of high-speed rolling-element bearings. |
