Evaluation of the real contact area in three-body dry friction by micro-thermal analysis

Abstract

International audienceMany tribological properties and wear mechanisms occurring on the micro-and nanoscale are strongly controlled by the so-called real contact area (Ar) which is a small fraction of the nominal or apparent contact area (Aa). The determination of Ar is often based on either (i) a geometrical approach describing the real geometry of contacting surfaces or (ii) a mechanical approach involving contact mechanics and physical-mechanical properties. In addition some experimental methods have also been attempted but they generally do not take into account the presence of third body at the interface--i.e. the wear debris trapped within the contact. In this paper we propose an experimental approach to estimate the dynamic real contact area from the operating parameters (Fn, v, T) and the tribological responses (μ, Ft) in presence of third body. A scanning thermal microscope (SThM) is used for determining both the thermal conductivity of the third body and the relationship between the contact temperature and the thermal power really dissipated at the micro-asperity level. These results are combined with a thermal model of the macro-tribocontact for computing the real contact area and the real contact pressure. Validation of these results is carried out using a classical Greenwood Williamson model and finite element models built from the real AFM maps

Experimental and Numerical Investigation of Friction Coefficient and Wear Volume in the Mixed-Film Lubrication Regime with ZnO Nano-Particle

“…Greenwood and Williamson (GW) originally introduced their model for rough surfaces (Stempflé et al 2010). Height distribution and asperity density considered in original GW model can be accounted for particle size distribution and nano-particle density between surfaces, respectively.…”

Effect of pressure changes in sliding contact

“…A spacetime-varying behaviour is the distinctive feature of sliding interaction [1][2][3][4]. The dynamical interaction between moving bodies is characterized by an abrasive effect on the surfaces and consequently wear and the change in the energy [5][6][7]. A part of the kinetic energy to overcome the friction in the contact area is converted to thermal energy [8,9] through the transfer of heat to the surroundings.…”

In situ running-in wear assessment in multi-asperity nanotribology

“…Besides, nanowear mechanisms met in various microsystems are generally closer to the polishing process in terms of wear rate [9] than the classical mechanisms of abrasion [10], adhesion [7] or ploughing [4,11,12]. This peculiar wear process mainly results from the combination of a low contact pressure and a closed multi-asperity tribocontact that acts as a triboreactor at the micro/nanoscale [13][14][15][16][17], where thermal effects [18], chemical and physico-chemical interactions [19,1,20,21,7], environment's influence [14,[22][23][24]15,19,25], and tribolayer are likely to control the tribological behavior, as a selforganization process [26,27,15,16,18,17].…”

“…In the latter case, physico-chemical aspects are superimposed on the mechanical ones. As a result, adhesive wear component also occurs leading to the formation of a self-organized tribolayer that usually controls both the friction and wear behaviors [39,27,26,15,16,18]. Thus, whatever its intrinsic accuracy [32,30], the main drawback of the topographical assessment is that any measurement is always carried out after the contact opening, meaning the loss of all the existing relationships between the frictional evolutions and the wear events.…”