Model for solid-liquid and solid-solid friction of rough surfaces with adhesion hysteresis.

Mechanisms of energy dissipation during solid-solid and solid-liquid friction are discussed. A conservative van der Waals adhesion force, when combined with surface imperfectness, such as deformation, leads to adhesion hysteresis (AH). When an asperity slides upon a substrate, the substrate is subjected to a loading-unloading cycle, and energy is dissipated due to the AH. Another mechanism, which leads to energy dissipation, involves energy barriers between metastable states due to surface roughness. Both mechanisms are fundamental for sliding and result in both solid-liquid and solid-solid friction.