Exploring the effect of geometric coupling on friction and energy dissipation in rough contacts of elastic and viscoelastic coatings

Abstract

We study the frictional behavior of both elastic and viscoelastic thin coatings in sliding rough contact in the presence of Coulomb friction at the interface, exploring the effect of the coupling between the normal and tangential displacement fields arising from the finiteness of the material thickness.We found that due to this so called geometric coupling asymmetric contacts and consequently keying friction are observed even for purely elastic contacts, indeed associated with zero bulk energy dissipation. Furthermore, enhanced keying friction is reported in the case of viscoelastic coatings compared to uncoupled contacts, this time entailing larger bulk energy dissipation.Geometric coupling also introduces additional interactions involving the larger scales in terms of normal displacements, which leads to a significant increase of the contact area, under given normal load, compared to the uncoupled case.These results show that, in the case of contact interfaces involving thin deformable coating bonded to significantly stiffer substrate, the effect of interfacial shear stresses cannot be neglected.