Abstract
The transition from ultra-thin lubrication to dry friction under high pressure and shear is studied using molecular dynamics: the quantity of lubricant in the confined film is progressively reduced toward solid-body contact. A quantized layer structure is observed for n-alkanes confined between smooth, wettable walls, featuring an alternation of well-layered, low friction configurations, and disordered ones, characterized by high friction, and heat generation. The molecular structure influences the ordering of the fluid and the resulting shear stress. In fact, Lennard-Jones fluids are characterized by low friction due to the absence of interlayer bridges, opposed to the always entangled states and high shear stresses for branched molecules. Surface geometry and wettability also affect the behavior of the confined lubricant. The presence of nanometer-scale roughness frustrates the ordering of the fluid molecules, leading to high friction states. Furthermore, local film breakdown can be observed when the asperities come into contact, with strong wall–wall interactions causing the maximum in shear stress. Finally, friction is limited to a small, constant value by the presence of smooth, non-wettable surfaces in the system due to the occurrence of wall slip.
Similar content being viewed by others
Abbreviations
- a, b, c :
-
Lattice constants in the x-, y- and z- directions
- λ, A :
-
Amplitude and wavelength of the nanometer-scale roughness
- c θ , θ :
-
Spring stiffness and equilibrium angle of the angle bending potential
- h :
-
Surface separation
- k b, l 0 :
-
Half spring stiffness and equilibrium length of the bond stretching potential
- k φ , n, d :
-
Dihedral force constant, multiplicity and phase shift of the CHARMM torsion potential
- L x , L y :
-
System dimensions in length and width
- m :
-
Molecular mass
- n C :
-
Number of CH x groups per surface unit
- \( n_{{{\text{CH}}_{x} ,{\text{mol}}}} \) :
-
Number of CH x groups per alkane molecule
- n mol :
-
Number of fluid molecules in the system
- P :
-
External pressure
- P adh :
-
Normal pressure due to adhesion
- r :
-
Interatomic distance
- S :
-
Area of the contact patch
- T f :
-
Fluid temperature
- T w :
-
Wall temperature
- u 1, u 2 :
-
Velocities of the upper and lower walls
- V b, V θ , V φ :
-
Potentials for the bonded interactions: covalent bond stretching, angle bending, and torsion
- V LJ :
-
Lennard-Jones potential for the non-bonded interactions
- ɛ, σ :
-
Energy and characteristic distance for the Lennard-Jones potential
- ρ :
-
Lubricant density
- τ zx :
-
Shear stress measured at the walls
References
Dowson, D.: History of Tribology. Longman, London (1979)
Robbins, M., Müser, M.: Modern Tribology Handbook, vol. 1, chap. 20: Computer Simulations of Friction, Lubrication, and Wear, pp. 717–765 CRC Press LLC (2001)
Gao, J., Luedtke, W., Landman, U.: Origins of solvation forces in confined films. J. Phys. Chem. B 101, 4013–4023 (1997)
Gao, J., Luedtke, W., Landman, U.: Structure and solvation forces in confined films: linear and branched alkanes. J. Chem. Phys. 106, 4309–4318 (1997)
Horn, R., Israelachvili, J.: Direct measurement of structural forces between two surfaces in a nonpolar liquid. J. Chem. Phys. 75, 1400–1411 (1981)
Gee, M., McGuiggan, P., Israelachvili, J., Homola, A.: Liquid to solid like transitions of molecularly thin films under shear. J. Chem. Phys. 93, 1895–1906 (1990)
Cui, S., Cummings, P., Cochran, H.: Structural transition and solid-like behavior of alkane films confined in nano-spacing. Fluid Phase Equilib. 183–184, 381–387 (2001)
Savio, D., Fillot, N., Vergne, P., Zaccheddu, M.: A model for wall slip prediction of confined n-alkanes: effect of wall-fluid interaction versus fluid resistance. Tribol. Lett. 46, 11–22 (2012)
Jabbarzadeh, A., Atkinson, J., Tanner, R.: The effect of branching on slip and rheological properties of lubricants in molecular dynamics simulation of couette shear flow. Tribol. Int. 35, 35–46 (2002)
Fillot, N., Berro, H., Vergne, P.: From continuous to molecular scale in modelling elastohydrodynamic lubrication: nanoscale surface slip effects on film thickness and friction. Tribol. Lett. 43, 257–266 (2011)
Martini, A., Roxin, A., Snurr, R., Wang, Q., Lichter, S.: Molecular mechanisms of liquid slip. J. Fluid Mech. 600, 257–269 (2008)
Jabbarzadeh, A., Atkinson, J., Tanner, R.: Effect of the wall roughness on slip and rheological properties of hexadecane in molecular dynamics simulation of couette shear flow between two sinusoidal walls. Phys. Rev. E 61, 690–699 (2000)
Berro, H.: A Molecular dynamics approach to nano-scale lubrication. PhD thesis, Villeurbanne, INSA de Lyon, October 11th, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0084/these.pdf (2010)
Gao, J., Luedtke, W., Landman, U.: Layering transitions and dynamics of confined liquid films. Phys. Rev. Lett. 79, 705–708 (1997)
Gao, J., Luedtke, W., Landman, U.: Structures, solvation forces and shear of molecular films in a rough nano-confinement. Tribol. Lett. 9, 3–13 (2000)
Persson, B., Ballone, P.: Boundary lubrication: layering transition for curved solid surfaces with long-range elasticity. Solid State Commun. 115, 599–604 (2000)
Sivebaek, I., Samoilov, V., Persson, B.: Squeezing molecular thin alkane films between curved solid surfaces with long-range elasticity: layering transitions and wear. J. Chem. Phys. 119, 2314–2321 (2003)
Persson, B., Mugele, F.: Squeeze-out and wear: fundamental principles and applications. J. Phys.: Condens. Matter 16, 295–355 (2004)
Samoilov, V., Sivebaek, I., Persson, B.: The effect of surface roughness on the adhesion of solid surfaces for systems with and without liquid lubricant. J. Chem. Phys. 121, 1997 (2004)
Tartaglino, U., Sivebaek, I., Persson, B., Tosatti, E.: Impact of molecular structure on the lubricant squeeze-out between curved surfaces with long range elasticity. J. Chem. Phys. 125(1), 014704 (2006)
Allen, M., Tildesley, D.: Computer Simulations of Liquids. Clarendon Press, Oxford (1987)
Kierfeld, J., Vinokur, V.: Lindemann criterion and vortex lattice phase transitions in type-II superconductors. Phys. Rev. B 69, 1–21 (2004)
Kittel, C.: Introduction to Solid State Physics, 7th edn. Wiley, NY (1995)
Jorgensen, W., Tirado-Rives, J.: The OPLS forcefield for proteins energy minimizations for crystals of cyclic peptides and crambin. J. Am. Chem. Soc. 110, 1657–1723 (1988)
Cornell, W., Cieplak, P., Bayly, C., Gould, I., Merz, K., Ferguson, D., Spellmeyer, D., Fox, T., Caldwell, J., Kollman, P.: A second generation force field for the simulation of proteins, nucleic acids and organic molecules. J. Am. Chem. Soc. 117, 5179–5197 (1995)
Xia, T., Ouyang, J., Ribarsky, M., Landman, U.: Interfacial alkane films. Phys. Rev. Lett. 69, 1967–1970 (1992)
Schneider, T., Stoll, E.: Molecular-dynamics study of a three-dimensional one-component model for distortive phase transitions. Phys. Rev. B 17, 1302–1322 (1978)
Berro, H., Fillot, N., Vergne, P., Tokumasu, T., Ohara, T., Kikugawa, G.: Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear. J. Chem. Phys. 135, 134708 (2011)
Berro, H., Fillot, N., Vergne, P.: Hybrid diffusion: an efficient method for kinetic temperature calculation in molecular dynamics simulations of confined lubricant films. Tribol. Lett. 37, 1–13 (2010)
Habchi, W., Vergne, P., Bair, S., Andersson, O., Eyheramendy, D., Morales-Espejel, G.: Influence of pressure and temperature dependence of thermal properties of a lubricant on the behaviour of circular TEHD contacts. Tribol. Int. 43, 1842–1850 (2010)
Somers, S., Davis, H.: Microscopic dynamics of fluids confined between smooth and atomically structured solid surfaces. J. Chem. Phys. 96, 5389–5407 (1992)
Christenson, H., Gruen, D., Horn, R., Israelachvili, J.: Structuring in liquid alkanes between solid surfaces: force measurements and mean-field theory. J. Chem. Phys. 87, 1834–1841 (1987)
Dowson, D., Higginson, G.: Elastohydrodynamic Lubrication, The Fundamentals of Roller and Gear Lubrication. Pergamon, Oxford (1966)
Gupta, S., Cochran, H., Cummings, P.: Nanorheology of liquid alkanes. Fluid Phase Equilib. 150–151, 125–131 (1998)
Kamei, D., Zhou, H., Suzuki, K., Konno, K., Takami, S., Kubo, M., Miyamoto, A.: Computational chemistry study on the dynamics of lubricant molecules under shear conditions. Tribol. Int. 36, 202–297 (2003)
Jabbarzadeh, A., Harrowel, P., Tanner, R.: Very low friction state of a dodecane film confined between mica surfaces. Phys. Rev. Lett. 94, 1–4 (2005)
Berman, A.D., Israelachvili, J.N.: Modern tribology handbook, vol. 1, chap. 16: Microtribology and Microrheology or Molecularly Thin Liquid Films, pp. 567–616, CRC Press LLC (2001)
Naidu, S., Klaus, E., Duda, J.: Evaluation of liquid phase oxidation products of ester and mineral oil lubricants. Ind. Eng. Chem. Prod. Res. Dev. 23, 613–619 (1984)
Naidu, S., Klaus, E., Duda, J.: Kinetic model for high-temperature oxidation of lubricants. Ind. Eng. Chem. Prod. Res. Dev. 25, 596–603 (1986)
Padilla, P.: Chemical structure effects on the equilibrium and under shear properties of thin films in confined geometries: a molecular dynamics simulation study. J. Chem. Phys. 103, 2157–2168 (1995)
Padilla, P., Toxvaerd, S.: Fluid alkanes in confined geometries. J. Chem. Phys. 101, 1490–1502 (1994)
Jabbarzadeh, A., Harrowel, P., Tanner, R.: Crystal bridge formation marks the transition to rigidity in a thin lubrication film. Phys. Rev. Lett. 96, 1–4 (2006)
Kelchner, C., Plimpton, S., Hamilton, J.: Dislocation nucleation and defect structure during surface indentation. Phys. Rev. B 58, 11085–11088 (1998)
Spijker, P., Anciaux, G., Molinari, J.-F.: Dry sliding contact between rough surfaces at the atomistic scale. Tribol. Lett. 44, 279–285 (2011)
Foiles, S., Baskes, M., Daw, M.: Embedded-atom-method functions for the FCC metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys. Phys. Rev. B 33, 7983–7991 (1986)
Lanke, U., Vedawyas, M.: Ion beam processing of oriented CuO films deposited on (1 0 0) YSZ by laser ablation. Nucl. Instrum. Methods Phys. Res. B 155, 97 (1999)
Rollmann, G., Rohrbach, A., Entel, P., Hafner, J.: First-principles calculation of the structure and magnetic phases of hematite. Phys. Rev. B 69, 165107 (2004)
Zhang, L., Balasundaram, R., Gehrke, S., Jiang, S.: Non equilibrium molecular dynamics simulations of confined fluids in contact with the bulk. J. Chem. Phys. 114, 6869–6877 (2001)
Minfray, C., Mogne, T.L., Martin, J.-M., Onodera, T., Nara, S., Takahashi, S., Tsuboi, H., Koyama, M., Endou, A., Takaba, H., Kubo, M., Carpio, C.D., Miyamoto, A.: Experimental and molecular dynamics simulations of tribochemical reactions with ZDDP: zinc phosphate-iron oxide reaction. Tribol. Trans. 51, 589–601 (2008)
Acknowledgments
The authors would to thank Mr. Alexander de Vries, Director SKF Group Product Development, for his kind permission to publish this article. This work was supported by SKF ERC, the Netherlands, and SKF Aeroengine France.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Savio, D., Fillot, N. & Vergne, P. A Molecular Dynamics Study of the Transition from Ultra-Thin Film Lubrication Toward Local Film Breakdown. Tribol Lett 50, 207–220 (2013). https://doi.org/10.1007/s11249-013-0113-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11249-013-0113-2