Sliding Viscoelastic Contacts: Reciprocating Adhesive Contact Mechanics and Hysteretic Loss

This study investigates the reciprocating motion of a rigid Hertzian indenter on a viscoelastic substrate with adhesion, using a finite element-based numerical model. An innovative methodology is employed to transform the sliding contact problem into an equivalent normal contact problem, enabling the accurate simulation of adhesion effects at the contact interface. The results reveal that system behaviour is governed by the interplay between viscoelasticity and adhesion, leading to notable changes in contact pressure distribution, contact area, and energy dissipation during reciprocating motion. Specifically, viscous dissipation within the substrate material dominates at intermediate sliding speeds, where the interaction between adhesion and viscoelastic relaxation processes results in pronounced hysteresis cycles. In contrast, at low and high sliding speeds (corresponding to the rubbery and glassy regions, respectively), the material behaviour is predominantly elastic, and no hysteresis is observed. Adhesion influences contact pressure distribution and contact size, particularly in the transition regime, where its effects on viscous dissipation are measurable. Moreover, the study clarifies that adhesion alone does not induce hysteresis in elastic regimes, distinguishing reciprocating contact from normal contact, where adhesive hysteresis is typically observed. New insights are also provided into how adhesion and viscoelasticity jointly impact tribological performance, offering a deeper understanding of energy dissipation mechanisms and contact mechanics during motion reversal. 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.