| Abstract: | Equilibrium conditions of a rigid cylinder in contact with the flat and smooth surface of a natural rubber sample are studied using concepts of fracture mechanics, such as the strain energy release rate or the stress intensity factor. It is shown that an equilibrium contact area exists if the applied force per unit axial length is greater than a negative critical value, closely related to the cylinder radius and mechanical and superficial properties of the elastic solid. Due to the intervention of molecular attraction forces, of van der Waals type, a light cylinder rolls under an inclined rubber surface and it is displayed that the rolling speed is the same when the cylinder rolls upon the same inclined surface. It has been verified that if a flat rubber substrate, with an adequate length, is rotated at constant angular velocity, a steel cylinder rolls alternately upon and under the surface, unceasingly without falling down. |
