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Shear-Induced Anisotropy in Rough Elastomer Contact

Antonio Papangelo's picture

R. Sahli, G. Pallares, A. Papangelo, M. Ciavarella, C. Ducottet, N. Ponthus, and J. Scheibert
Phys. Rev. Lett. 122, 214301 –

True contact between randomly rough solids consists of myriad individual microjunctions. While their total area controls the adhesive friction force of the interface, other macroscopic features, including viscoelastic friction, wear, stiffness, and electric resistance, also strongly depend on the size and shape of individual microjunctions. We show that, in rough elastomer contacts, the shape of microjunctions significantly varies as a function of the shear force applied to the interface. This process leads to a growth of anisotropy of the overall contact interface, which saturates in the macroscopic sliding regime. We show that smooth sphere-plane contacts have the same shear-induced anisotropic behavior as individual microjunctions, with a common scaling law over 4 orders of magnitude in the initial area. We discuss the physical origin of the observations in light of a fracture-based adhesive contact mechanics model, described in the companion article, which captures the smooth sphere-plane measurements. Our results shed light on a generic, overlooked source of anisotropy in rough elastic contacts, not taken into account in current rough contact mechanics models

The companion paper can be found here:


Mike Ciavarella's picture

Interestingly (but we reported only part of this and hidden in the Suppl. Mat.) we found that rough surfaces we measured (standard metal ones used to mold the soft material) had power law PSD, but with strange non-fractal features (apparent fractal dimension lower than two, clusters of contact much more regular than what commonly described), quite far from the common ideal fractal most of the modern community describes, including gaussian heigths, but highly non gaussian slopes and curvatures. So PSD is power law but this doesn't mean we can use the common results. But we haven't gone deep into this.

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