Thin Film Lubrication for Large Colloidal Particles:  Experimental Test of the No-Slip Boundary Condition

2007 ◽  
Vol 111 (44) ◽  
pp. 16300-16312 ◽  
Author(s):  
Christopher D. F. Honig ◽  
William A. Ducker
Keyword(s):  
Thin Film ◽  
Boundary Condition ◽  
Experimental Test ◽  
Colloidal Particles ◽  
Slip Boundary Condition ◽  
Thin Film Lubrication ◽  
Slip Boundary ◽  
Film Lubrication

scholarly journals Impact of chosen force fields and applied load on thin film lubrication

Friction ◽  
2021 ◽  
Author(s):  
Thi D. Ta ◽  
Hien D. Ta ◽  
Kiet A. Tieu ◽  
Bach H. Tran
Keyword(s):  
Thin Film ◽  
Shear Stress ◽  
Surface Structure ◽  
Rheological Properties ◽  
Surface Potential ◽  
Applied Load ◽  
Velocity Slip ◽  
Thin Film Lubrication ◽  
Lubrication Performance ◽  
Film Lubrication

AbstractThe rapid development of molecular dynamics (MD) simulations, as well as classical and reactive atomic potentials, has enabled tribologists to gain new insights into lubrication performance at the fundamental level. However, the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately. This extensive study analyzed the effects of surface structure, applied load, and force field (FF) on the thin film lubrication of hexadecane. The lubricant film became more solid-like as the applied load increased. In particular, with increasing applied load, there was an increase in the velocity slip, shear viscosity, and friction. The degree of ordering structure also changed with the applied load but rather insignificantly. It was also significantly dependent on the surface structure. The chosen FFs significantly influenced the lubrication performance, rheological properties, and molecular structure. The adaptive intermolecular reactive empirical bond order (AIREBO) potential resulted in more significant liquid-like behaviors, and the smallest velocity slip, degree of ordering structure, and shear stress were compared using the optimized potential for liquid simulations of united atoms (OPLS-UAs), condensed-phase optimized molecular potential for atomic simulation studies (COMPASS), and ReaxFF. Generally, classical potentials, such as OPLS-UA and COMPASS, exhibit more solid-like behavior than reactive potentials do. Furthermore, owing to the solid-like behavior, the lubricant temperatures obtained from OPLS-UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF. The increase in shear stress, as well as the decrease in velocity slip with an increase in the surface potential parameter ζ, remained conserved for all chosen FFs, thus indicating that the proposed surface potential parameter ζ for the COMPASS FF can be verified for a wide range of atomic models.

Mechanism of Boundary Lubrication and the Edge Effect

1965 ◽  
Vol 87 (3) ◽  
pp. 735-739 ◽  
Author(s):  
Y. Tamai ◽  
B. G. Rightmire
Keyword(s):  
Thin Film ◽  
Acid Solution ◽  
Palmitic Acid ◽  
Boundary Lubrication ◽  
Frictional Resistance ◽  
Copper Surface ◽  
Bulk Liquid ◽  
Attraction Force ◽  
Thin Film Lubrication ◽  
Film Lubrication

Experimental work was carried out on the boundary lubrication of a copper-copper couple with pure cetane, palmitic acid solution of cetane, and some other organic materials. The purpose was to get information about α and μlube, which appear in the friction equation: μ=αμsolid+(1−α)μlube, by using two different kinds of copper surface, a clean surface, and an oxidized surface. α was found to be small with palmitic acid solution, and the estimated shear strength of palmitic acid was high under the examined condition. α and μlube seemed to be properties which are independent of each other. α is closely related to the attraction force between the lubricant and the substrate, whereas μlube is related to the complexity of molecular structure of the lubricant. A comparison was made of bulk-liquid and thin-film lubrication. μlube was smaller in thin-film lubrication than it was in bulk-liquid lubrication. This suggests that the frictional resistance may be partly contributed by liquid in the edge space around the real contact.

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