Crack-front model for adhesion of soft elastic spheres with chemical heterogeneity

On the adhesion between thin sheets and randomly rough surfaces

“…Nonetheless, it seems somewhat easier to reach a state of saddle-point contact for randomly rough than for single-wavelength indenters, since the latter have an extreme propensity to form full contact, once the saddle points touch the elastomer. This work, like our previous one (Wang and Müser, 2022), supports the idea of the possibility of energy loss due to contact hysteresis even without viscoelasticity (Dalvi et al, 2019;Li et al, 2019;Sanner and Pastewka, 2022). While these works were concerned with a semi-infinite elastomer interacting with a nominally flat Hertzian indenter, Li et al (2019) found, as we did, a relative sharp transition between sticky and unsticky when a "Johnson adhesion parameter" α* took a value near 0.25.…”

Why soft contacts are stickier when breaking than when making them

“…The energy release rate G at a given point now depends on the whole shape of the contact a ( s ), where s is the length of the corresponding path along the contact circle. On the basis of the crack perturbation theory by Gao and Rice ( 9 , 10 , 22 ), we recently derived the approximate expression ( 9 , 11 )Gfalse(sfalse)=GJKRfalse[a(s)false]+c(−normalΔs)1/2afalse(sfalse)for the energy-release rate. Equation 3 has a simple interpretation: The adhesive contact line, a ( s ), behaves like an elastic line.…”

“…We use a crack perturbation model (9)(10)(11) to compute the energy release rate at the perimeter of the contact and solve for equilibrium with the local (equivalent) fracture energy w loc using the algorithm by Rosso and Krauth (45). The derivation of the crack perturbation equations and the mapping from surface roughness to the equivalent work-of-adhesion heterogeneity is provided in the Supplementary Materials.…”

“…In this article, we show that adhesion hysteresis emerges even for perfectly elastic contacts and in the absence of contact aging and viscoelasticity because of surface roughness. We present a crack perturbation model (9)(10)(11) and experimental observations that reveal discrete jumps of the contact perimeter. These stick-slip instabilities are triggered by local differences in fracture energy between roughness peaks and valleys.…”

Modeling the surface topography dependence of friction, adhesion, and contact compliance

“…The difficulty in modeling adhesive multistability lies in the need for short-ranged adhesion, 58 which entails the necessity for an extremely fine discretization to avoid spurious effects. 59 Sanner and Pastewka found a rather compelling solution to this problem for spherical indenters with small-scale roughness 60 by mapping it onto a crack-front model with quenched disorder, 61 which can prove useful to describe the motion of a contact line of a liquid droplet on a substrate. 62 To this end, they first exploited the possibility to express the elastic energy of a singly connected contact domain as a function of its contour.…”