Surface textures and non-Newtonian fluids for decreased friction in full film lubrication

Lubrication;Surface Textures;Non-Newtonian Fluids;Reynolds Equation

Schuh, Jonathon Kenneth

关键词: Lubrication;    Surface Textures;    Non-Newtonian Fluids;    Reynolds Equation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78561/SCHUH-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Surface texturing has been studied extensively to decrease friction in lubricated sliding contact. The majority of the previous experimental work has focused on symmetric-depth-surface textures. This work examines both symmetric and asymmetric surface textures in order to determine the effects of asymmetry on friction reduction. Gap controlled experiments with Newtonian fluids were performed on a custom tribo-rheometer in order to measure the normal force production and apparent viscosity reduction due to the surface textures. This work shows that symmetry must be broken in order to produce normal forces with surface textures which are caused by viscous effects for gap based Reynolds Number up to 1.21.The experimental results with Newtonian fluids suggest that there is an optimal surface texture configuration for decreasing friction. In order to determine the optimal texture configuration, numerical methods must be used in order to solve a mathematical model describing the lubricated system. The experimental work shows that the normal forces are produced due to viscous effects, allowing the Reynolds equation to be used as the mathematical model for the lubricated system. A pseudo-spectral method is used to solve the Reynolds equation in cylindrical coordinates. Exponential convergence is shown with this solution method and favorable results to the experimental results are shown, validating the numerical method for use in optimization of the surface textures. A recent trend in the lubrication industry has been to add polymer additives to base oils in order to increase their effectiveness as lubricants. These polymer additives, however, cause the oil to become a Non-Newtonian viscoelastic lubricant. The final portion of this work presents the first experimental investigation of surface textures with viscoelastic lubricants in order to determine asymmetric and Non-Newtonian effects on friction reduction. Gap controlled experiments are performed on the same custom tribo-rheometer in order to measure the normal force production and apparent viscosity reduction. This work shows that symmetry must be broken in order to produce normal forces above the viscoelastic response and that an optimal asymmetric texture exists for decreasing friction with viscoelastic lubricants.