Closely piling up of multiple adhesive fronts in adhesive friction due to re-attachment

To understand why the adhesive frictional force was in linear proportion to the real contact area in experiments, we investigate the adhesive friction generated by sliding elastic solids adhered to a rigid surface via multiple adhesive springs. Our results indicate that the shear-off force of the interface increases with the energetically guided re-attachment rate of adhesive springs, reaching saturation at high re-attachment rates. Remarkably, this shear-off force can surpass the predictions made by the fracture theory. By plotting the adhesive forces along the interface, we observe substantial high adhesive forces distributed throughout the interface, based on which we identify multiple adhesive fronts closely piling up along the interface. These regions can exhibit similar force profiles, and their number appears to increase with the size of the interface, leading to a linear increase in the calculated shear-off force with the size of the interface. We then suggest that multiple adhesive fronts closely pile up to back up each other in adhesive friction due to re-attachments, which may provide profound insights into understanding the observed phenomena associated with adhesive friction along an interface.