Rate-dependent adhesion of viscoelastic contacts. Part II: numerical model and hysteresis dissipation

TL;DR

This paper introduces a numerical model for viscoelastic adhesive contact that captures hysteresis due to viscous dissipation, showing how detachment rate and roughness influence adhesion energy and force.

Contribution

It presents a novel numerical contact model that separates material dissipation from elastic instability, validated against experiments for viscoelastic rough contacts.

Findings

Pull-off force depends on detachment rate and roughness amplitude.

Hysteresis is mainly due to viscous energy dissipation at contact lines.

Surface energy decreases with contact area reduction, less affected by contact boundary changes.

Abstract

In this paper, we propose a numerical model to describe the adhesive normal contact between a "rigid" spherical indenter and a viscoelastic rough substrate. The model accounts for dissipative process under the assumption that viscoelastic losses are localized at the (micro)-contact lines. Numerical predictions are then compared with experimental measurements, which show a strong adhesion hysteresis mostly due to viscous energy dissipation occurring during pull-off. This hysteresis is satisfactorily described by the contact model which allows to distinguish the energy loss due to material dissipation from the adhesion hysteresis due to elastic instability. Our analysis shows that the pull-off force required to detach the surfaces is strongly influenced by the detachment rate and the rms roughness amplitude, but it is almost unaffected by the maximum load from which unloading starts. Moreover, the increase in the boundary line separating contact and non-contact regions, observed when moving from smooth to rough contacts, negligibly affects the viscous dissipation. Such increase is much less significant than the reduction in contact area, which therefore is the main parameter governing the strong decrease in the effective surface energy.