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Abstract: Digital Image Correlation is used to study the micromechanics of amulti-contact interface formed between a rough elastomer and a smooth glasssurface. The in-plane elastomer deformation is monitored during the incipientsliding regime, i.e. the transition between static and sliding contact. As theshear load is increased, an annular slip region, in coexistence with a centralstick region, is found to progressively invade the contact. From theinterfacial displacement field, the tangential stress field can be furthercomputed using a numerical inversion procedure. These local mechanicalmeasurements are found to be correctly captured by Cattaneo and Mindlin CM-smodel. However, close comparison reveals significant discrepancies in both thedisplacements and stress fields that reflect the oversimplifying hypothesisunderlying CM-s scenario. In particular, our optical measurements allow us toexhibit an elasto-plastic like friction constitutive equation that differs fromthe rigid-plastic behavior assumed in CM-s model. This local constitutive law,which involves a roughness-related length scale, is consistent with the modelof Bureau \textit{et al.} Proc. R. Soc. London A \textbf{459}, 2787 2003derived for homogeneously loaded macroscopic multi-contact interfaces, thusextending its validity to mesoscopic scales.measurements allow for the firstquantitative test of Cattaneo and Mindlin CM classical model of the incipientsliding of a smooth interface. Small deviations are observed and interpreted asa result of the finite compliance of the rough interface, a behavior whichcontrasts with Amontons- law of friction assumed to be valid locally in CM-smodel. We illustrate how these measurements actually provide a method forprobing the rheology of the rough interface, which we find to be of theelasto-plastic type.



Author: Alexis Prevost, Julien Scheibert LTDS, Georges Debrégeas

Source: https://arxiv.org/







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