The interaction between adhesion and friction in soft contacts represents a challenging topic in tribology, as it is relevant in key technical applications such as soft robots, seals, human-robot interactions, bio-engineering, pressure-sensitive adhesives. For example, by controlling interfacial adhesion one could develop smart surfaces capable to transmit tactile feedbacks to human beings. It is well known that when soft adhesive contacts are sheared by tangential forces, the contact area tends to shrink, reducing especially along the direction of the applied shearing load, before gross slip happens. In the shearing process, there is a certain degree of interaction between the adhesive tractions established in the direction normal to the contact and the frictional tractions acting in the plane of contact, which is well captured by exploiting mixed-mode models in Linear Elastic Fracture Mechanics (LEFM). We will show that LEFM is able to predict experimental results with great accuracy. Nevertheless, further work is needed to clarify the effect of large deformations on the contact patch shrinking. We will revise the latest advancements in this field pointing to the present modeling challenge of having to include the effect of viscoelasticity, as commonly observed in soft materials.
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