Loading-unloading hysteresis loop of randomly rough adhesive contacts

TL;DR

This study investigates how roughness and adhesion forces cause hysteresis in the loading-unloading behavior of soft solids in contact, revealing energy loss due to metastable states and surface properties.

Contribution

It introduces a spectral method to generate self-affine fractal rough surfaces and quantifies hysteretic energy loss in adhesive contacts.

Findings

Hysteresis loop results from roughness and adhesion forces.

Energy loss occurs due to metastable states.

Surface properties influence hysteresis magnitude.

Abstract

In this paper we investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave-vectors. A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged, and the calculated contact area and applied load are shown as a function of the penetration, for loading and unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process.