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Tribologists are confronted on a daily basis by the need to understand the causes and consequences of friction on the behaviour of bodies in contact. Understanding contact behaviour is not only a scientific curiosity but the key to solving numerous industrial issues. Numerical tools have been developed to overcome the problems encountered in experiments due to limitations in the local dynamic analysis of multi-scale systems (mechanisms, bodies in contact, interfaces). More than an exhibition of numerical results, the present paper proposes reviewing the literature on the numerical tribology of dry contacts by analysing the different scales involved. © 2011 Elsevier Ltd. All rights reserved

This article describes molecular dynamics simulations of an ionic liquid (IL) confined between iron oxide surfaces under relatively high pressure and severe shearing, representative of a typical steel-steel lubricated contact. The simulations reveal the presence of hydrodynamic and thermal slip at the walls, despite the wetting nature of the fluid/wall interface. A crucial consequence of the temperature slip is the subsequent increase of the fluid temperature under shear, which modifies its effective rheology, resulting in saturation of the shear stress at high shear rates. Overall, this article provides a methodology for accurate modeling of tribological contacts lubricated by a nanometer-thick IL film. The results contribute to the debate on the saturation of the shear stress at high shear rates, and reveal the rich phenomenology arising in severe tribological conditions, departing from the traditional understanding of nanofluidic transport, mainly built in the linear response regime and standard thermodynamic conditions.

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Energy is commonly dissipated in molecular dynamics simulations by using a thermostat. In non-isothermal shear simulations of confined liquids, the choice of the thermostat is very delicate. We show in this paper that under certain conditions, the use of classical thermostats can lead to an erroneous description of the dynamics in the confined system. This occurs when a critical shear rate is surpassed as the thermo-viscous effects become prominent. In this high-shear-high-dissipation regime, advanced dissipation methods including a novel one are introduced and compared. The MD results show that the physical modeling of both the accommodation of the surface temperature to liquid heating and the heat conduction through the confining solids is essential. The novel method offers several advantages on existing ones including computational efficiency and easiness of application for complex systems.