Isothermal Line Contact Viscoplastic Fluid Elastohydrodynamic Lubrication

Lubricating oil in EHL (Elastohydrodynamic Lubrication) contact zone bears high pressure, high temperature, and high shear strain rate in short time, and shows the property as a non-Newtonian fluid. So it can't be described by conventional EHL theory that is based on Newtonian fluid model. Especially in the condition of high rolling speeds, heavy loads and large slide-roll ratios, practically line and point contact Elastohydrodynamic Lubrication (EHL)has proved to drastically deviate from conventional EHL theory. In such condition, the actual EHL film is much thinner than that conventional EHL theory predicts or even disappears. This indicates conventional EHL theory is actually inadequate. The current theoretical studies on EHL film failure mainly focus attention on the effects on EHL of the lubricant film viscous heating, contact surface roughness and lubricant non-Newtonian property. By those studies the EHL film is found to be thinner but not disappear. Therefore, the current EHL theories are still not applicable for EHL failure design.Based on the fact of solid strength failure, the present research does not follow the conventional views on EHL film failure. It explains EHL film collapse and failure from the lubricant film shear strength effect, and explores the relationship of EHL film loading carrying capacity with lubricant shear strength by theory. Actually, it is to investigate the relationship of lubricant viscoplastic effect with EHL film collapse.The main research work in this dissertation is as follows:1. Soft ware for isothermal Newtonian EHL line contact problem is drawn up. Numerical calculation results are in accordance with the results of classical EHL theory2. Soft ware for isothermal ideal viscoplastic fluid EHL line contact problem is drawn up. Numerical calculation results show that lubricant shear strength does make pressure distribution, oil film thickness and profile, and traction coefficient different from the results predicted by classical EHL theory.3. Soft ware for isothermal Evans-Johnson fluid EHL line contact problem is drawn up. Numerical calculation results show that oil film thickness and the amount of oil fluxing in contact area are different from the results based on idealviscoplastic fluid EHL when both shear strength non-Newtonian property and Eyring non-Newtonian property are considered.4. The central oil film formula and minimum oil film formula are regressed in the condition of heavy loads.5. Limit shear strength formula of oil film is regressed. Lubricating oil can be chosen according to this formula in the practical condition in order to prevent lubrication failure.6. The central oil film formula including lubricant shear strength is regressed. This formula reflects the practical condition more accurately compared to classical EHL oil film formula. It can be applicable for EHL failure design.