<p>Non-equilibrium molecular dynamics (NEMD) simulations were carried out to investigate the lubrication of two amorphous carbon surfaces by a confined fluid of n-hexadecane molecules. Interatomic interactions were described by the AIREBO-M potential. An external pressure of 1&#xa0;GPa and shear rates in the range of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(10^9\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>10</mn> <mn>9</mn> </msup> </math></EquationSource> </InlineEquation>–<InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(10^{10}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>10</mn> <mn>10</mn> </msup> </math></EquationSource> </InlineEquation>&#xa0;s<InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation> were applied to the system. Subjected to this high shear rates, above the critical shear rate, the n-hexadecane fluid behaved as a non-Newtonian fluid. Slip-boundary behavior was not observed, but the system demonstrated shear localization. Due to stronger interactions at the solid–lubricant interface, where some n-hexadecane molecules were adsorbed, the corresponding sublayers of lubricant molecules moved with the same velocity of the sliding surfaces. Away from the interfaces, a linear velocity profile, consistent with Couette flow, developed towards the center of the fluid channel. The friction coefficients calculated from the mean shear stresses were in the ultra-low friction region, which is compatible with experimental data for similar tribosystems.</p>

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Non-equilibrium Molecular Dynamics Study of the Tribological Behavior of Lubricated Amorphous Carbon

  • Rebeca Q. Stelle,
  • Roberto Gomes de Aguiar Veiga,
  • Marcio G. Di V. Cuppari

摘要

Non-equilibrium molecular dynamics (NEMD) simulations were carried out to investigate the lubrication of two amorphous carbon surfaces by a confined fluid of n-hexadecane molecules. Interatomic interactions were described by the AIREBO-M potential. An external pressure of 1 GPa and shear rates in the range of \(10^9\) 10 9 \(10^{10}\) 10 10  s \(^{-1}\) - 1 were applied to the system. Subjected to this high shear rates, above the critical shear rate, the n-hexadecane fluid behaved as a non-Newtonian fluid. Slip-boundary behavior was not observed, but the system demonstrated shear localization. Due to stronger interactions at the solid–lubricant interface, where some n-hexadecane molecules were adsorbed, the corresponding sublayers of lubricant molecules moved with the same velocity of the sliding surfaces. Away from the interfaces, a linear velocity profile, consistent with Couette flow, developed towards the center of the fluid channel. The friction coefficients calculated from the mean shear stresses were in the ultra-low friction region, which is compatible with experimental data for similar tribosystems.