# Resolving a controversy about adhesion in sliding contacts

## TL;DR

This paper critically examines a recent claim that tangential shear stresses increase contact area in sliding adhesive contacts, providing a thermodynamic analysis that aligns with classical theories and highlights the need for considering dissipative effects.

## Contribution

It offers a rigorous thermodynamics calculation that clarifies the relationship between shear stresses and contact area, resolving a controversy and aligning with classical models.

## Key findings

- Thermodynamics analysis shows no increase in contact area due to shear stresses.
- The model predicts a stronger reduction in contact area than classical theories.
- Dissipative effects are necessary to reconcile theory with experimental observations.

## Abstract

An interesting recent paper by Menga, Carbone & Dini (MCD, 2018, [1]), suggests that in sliding adhesive contacts, the contact area should increase due to tangential shear stresses at the interface, assumed to be constant and corresponding to a material constant. This is not observed in the known experiments, and is in sharp contrast with all the classical theories about the transition from stick to sliding, both in the JKR (Griffith like) conditions which involve singular pressure and shear, as well as in full general cohesive models. We offer a rigorous thermodynamics calculation, which suggests in fact there is no qualitative contrast but a very close quantitative agreement, with previous theories. Actually, the model predicts an even stronger reduction of contact area than predicted by Savkoor and Briggs, contrary to experimental observations, so would certainly require some adjustements to consider dissipative effects.