Sliding viscoelastic contacts: Reciprocating adhesive contact mechanics and hysteretic loss

Abstract In this study, we investigate the reciprocating motion of a rigid Hertzian indenter on a viscoelastic substrate with adhesion. We employ a numerical model based on finite element analysis to simulate the problem, utilizing an innovative methodology for solving the sliding problem in the presence of adhesion at the contact interface. The results show that the behaviour of the system is influenced by both viscoelasticity and adhesion, leading to significant changes in contact pressure distribution and contact length during each cycle of motion. The effect of sliding speed on these parameters is also explored, revealing different regimes in relation to frequency-dependent material response. Energy loss in a reciprocating cycle is primarily attributed to viscous dissipation within the substrate material, which is activated at intermediate sliding speeds. In the rubbery (low speeds) and glassy (high speeds) regions, where the material behaviour is predominantly elastic, no hysteresis is observed in the frictional behaviour. Adhesion has a noticeable impact on both contact pressure distribution and contact length variation during each cycle; however, has no direct effect on dissipation. This is a relevant result that helps to clarify some previous interpretations of experimental tests. Interestingly, our results also show that there is a lag period after motion reversal where friction aligns with motion direction before eventually changing direction as pressure redistribution occurs within the system. This phenomenon highlights how changes in contact mechanics affect local tribological interactions and can lead to variations in overall system response.