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Conference Papers Year : 2012

From full film lubrication to local film breakdown: a molecular dynamics approach

Daniele Savio
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  • PersonId : 764837
  • IdRef : 176609148
Nicolas Fillot
Philippe Vergne
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  • PersonId : 839328
Maurizio Zaccheddu
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Molecular dynamics simulations are used to analyze the local tribological behaviour of n-hexadecane confined between metal oxide surfaces under high pressure and shear rates. The number of lubricant molecules in the contact zone is then progressively reduced in order to achieve the direct contact between the atoms of the walls. Furthermore, the influence of the surface wettability and geometry (smooth versus nanorough surfaces) is studied. A particular focus is placed on the analysis of the structure and dynamics of the confined fluid. Results show that, in the case of smooth surfaces, two possible configurations can be reached. In some cases, a well defined structure is formed by the lubricant molecules, with an integer number of layers having equal density and low bridging. Between these ordered states, transition zones can be observed: the central layers merge together, and a disordered state is achieved in the center of the film. Finally, the ordering inside the fluid is always frustrated when nanometer scale roughness is present. Surface nature and geometry have a significant effect on the dynamics of the confined lubricant and friction. In the case of smooth wettable walls the lubricant is locked to the surfaces and shearing occurs between layers. Shear stress is then related to the degree of organization within the fluid: it oscillates from minima (in correspondence with ordered states), to maxima (at the transitions between well defined layers). On the other hand, wall slip at the fluid-surface interface occurs for smooth, non wettable surfaces: the shear stress is limited to a low, constant value. Nanorough surfaces cause a disordered state in the lubricant, and frustrate the occurrence of wall slip: hence, high friction ensues.


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Dates and versions

hal-00862945 , version 1 (17-09-2013)


  • HAL Id : hal-00862945 , version 1


Daniele Savio, Nicolas Fillot, Philippe Vergne, Maurizio Zaccheddu. From full film lubrication to local film breakdown: a molecular dynamics approach. 2012 ASME/STLE International Joint Tribology Conference,, Oct 2012, Denver (Colorado), United States. pp.USB stick. ⟨hal-00862945⟩
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