Rough viscoelastic sliding contact: Theory and experiments

Abstract

In this paper, we show how the numerical theory introduced by the authors [Carbone and Putignano, J. Mech. Phys. Solids 61, 1822 (2013)] can be effectively employed to study the contact between viscoelastic rough solids. The huge numerical complexity is successfully faced up by employing the adaptive nonuniform mesh developed by the authors in Putignano et al. [J. Mech. Phys. Solids 60, 973 (2012)]. Results mark the importance of accounting for viscoelastic effects to correctly simulate the sliding rough contact. In detail, attention is, first, paid to evaluate the viscoelastic dissipation, i.e., the viscoelastic friction. Fixed the sliding speed and the normal load, friction is completely determined. Furthermore, since the methodology employed in the work allows to study contact between real materials, a comparison between experimental outcomes and numerical prediction in terms of viscoelastic friction is shown. The good agreement seems to validate-at least partially-the presented methodology. Finally, it is shown that viscoelasticity entails not only the dissipative effects previously outlined, but is also strictly related to the anisotropy of the contact solution. Indeed, a marked anisotropy is present in the contact region, which results stretched in the direction perpendicular to the sliding speed. In the paper, the anisotropy of the deformed surface and of the contact area is investigated and quantified.

Mechanics of rough contacts in elastic and viscoelastic thin layers

“…Furthermore, also the anisotropy of the contact solution decreases with the thickness, thus confirming the affinity between friction and contact anisotropy suggested by the authors in [52]. In Figure 7, we plot in a polar diagram m 2 (θ) that is the average square slope of the a profile obtained by cutting the deformed surface u (x; ζ 1 , ζ 2 ) along the direction θ [51], for different values of the thickness.…”

“…The proposed periodic formulation provides original tools to explore a wide range of contact problems in the presence of layered bodies and enables us to overcome some of the limitations of the formulations proposed in Refs. [3] and [52]. Therefore, the newly developed algorithm has been used to perform a systematic investigation of a variety of contact problems characterised by layered elastic and viscoelastic materials subjected to various loads and sliding speeds.…”

“…Human skin is just an example of a layered system where finite size effects cannot be neglected ( [59], [60]). To tackle contact problems related to these interesting topics, we derive a boundary element formulation which modifies the methodologies presented in [33] and [52] to account for the finite thickness layers made of both elastic and viscoelastic materials. The formulation is further improved to include a fast numerical periodic solver that allows simulating large contact domains (Section II).…”

Static friction between rigid fractal surfaces

“…Suh and Sin [10] argued that the deformation and ploughing of surface asperities account only for a part of the observed frictional force and that there is a significant contribution due to atomic-scale mechanisms acting at the flat portions of the sliding surface. Studies of these atomic mechanisms have shown that friction can dramatically depend on the chemical and atomic nature of surfaces [36,37], with the observed friction coefficient often being load dependent [36,38].…”

“…For this reason fractal analysis is increasingly used as a meaningful cross-scale descriptor to characterize and define surface structures and model interfacial contact mechanics [4][5][6][7]. Indeed, it has been shown for elastic and viscoelastic systems that understanding and interpreting frictional interactions at static or low-velocity conditions necessitate the consideration of the multiscale nature of solid interfaces [8][9][10].…”