Theory of viscoelastic adhesion and friction

TL;DR

This paper introduces a new theoretical framework for understanding viscoelastic adhesion and friction, accounting for energy balance and predicting velocity-dependent energy release rates and increased hysteretic friction, validated by experimental data.

Contribution

It develops a rigorous local energy balance formulation for viscoelastic contact with adhesion, revealing non-monotonic energy release rates and enhanced hysteretic friction effects.

Findings

G1 and G2 vary non-monotonically with velocity

Hysteretic friction is significantly increased by adhesion

Predictions match experimental observations

Abstract

We present a novel theory of the adhesive contact of linear viscoelastic materials against rigid substrates moving at constant velocity. Despite the non-conservative behavior of the system, the closure equation of the contact problem can be rigorously formulated in the form of a local energy balance. In the case of adhesiveless contacts, this is equivalent to enforce the stationarity of the total energy stored into the viscoelastic material. However, in the presence of interfacial adhesion, the appearance of non-conservative terms leads to different values of the energy release rates G1 and G2 at the contact trailing and leading edges, respectively. Specifically, the present theory predicts a non-monotonic trend of G1 and G2 as function of the indenter velocity, as well as a very significant enhancement of hysteretic friction due to the coupling between adhesion and viscoelasticity, compared to the adhesiveless case. Both predictions are in very good agreement with existing experimental data.