Onset of Sliding of Elastomer Multicontacts: Failure of a Model of Independent Asperities to Match Experiments

Abstract

Modelling of rough frictional interfaces is often based on asperity models, in which the individual behaviour of individual microjunctions is assumed. In the absence of local measurements at the microjunction scale, quantitative comparison of such models with experiments is usually based only on macroscopic quantities, like the total tangential load resisted by the interface. Recently however, a new experimental dataset was presented on the onset of sliding of rough elastomeric interfaces, which includes local measurements of the contact area of the individual microjunctions. Here, we use this more comprehensive dataset to test the possibility of quantitatively matching the measurements with a model of independent asperities, enriched with experimental information about the area of microjunctions and its evolution under shear. We show that, despite using parameter values and behaviour laws constrained and inspired by experiments, our model does not quantitatively match the macroscopic measurements. We discuss the possible origins of this failure.

Finite deformations govern the anisotropic shear-induced area reduction of soft elastic contacts

“…Such a similarity across scales suggests that the present conclusions may also be used to further understand the shear behaviour of soft material multicontacts, the modelling of which may require non-linear elasticity. This may in particular be an explanation for the fact that, in Scheibert et al (2020), a multi-asperity model based on linear elasticity failed to reproduce quantitatively the multicontact results of Sahli et al (2018).…”

An asperity-based statistical model for the adhesive friction of elastic nominally flat rough contact interfaces

“…The hook-like portions at the right end of A r (F x ) curves can hardly be reproduced at the same time because, in the experiments, it is presumably an unstable dynamic feature caused by stick-slip. A better solution for fixing this mismatch might be to use the dynamic formulation proposed by Scheibert et al[12].We are now in a position to comment on the previous model by Scheibert et al[12], already mentioned in the Introduction. They developed an asperity-based dynamic contact model in which the real contact area is composed of multiple elliptic contact spots.…”

“…Although the model parameter values used in the illustrations of section 4 are inspired by actual experimental observations, only in section 5 do we address the challenging question of how to extract the relevant topographical and material parameters enabling a quantitative comparison with experiments. Indeed, in section 5, we apply our model to the conditions of the experiments of Sahli et al [5], quantitatively compare the predictions with the observations, and discuss the outcome with respect to that of the previous modeling attempt of [12]. , with w being the work of adhesion and ≈ 0.2 nm as the equilibrium distance between atoms, is assumed to be larger than 5 so that the adhesive contact is within the Johnson, Kendall and Roberts (JKR) limit [37].…”

An asperity-based statistical model for the adhesive friction of elastic nominally flat rough contact interfaces

“…To the authors knowledge, there has been only one attempt in this direction in the literature: that of Scheibert et al [12]. They proposed a dynamic independent-asperity model aimed at reproducing quantitatively the experimental results obtained in [5].…”