Influence of surface properties on the rebound of a rigid ball on a rubber surface

It is well-known that molecular attraction forces, of the van der Waals type for rubber-like materials, act in the contact area between a polished and cleaned rigid ball and the smooth and flat surface of a rubber sheet; they increase the size of this contact area compared with the value which can be deduced from the classical theory of elasticity. Moreover, numerous experiments have shown that these forces are responsible for the existence of a kinetics of detachment in a pull-off test. In this study, we demonstrate that these long-range attractive forces also alter drastically the rebound of a rigid ball on a rubber surface. It is shown that during the movement of the ball out of contact with the rubber,work is done to peel the rubber off the ball surface and that this energy is the amount by which the surface adhesion effect reduces the resilience. A simple energy balance theory allows us to predict the rebound height and we show that there is a critical drop height below which the ball sticks and does not bounce at all. It is demonstrated that the simple energy balance theory proposed gives a correct prediction of the various observed rebound heights for several balls, when the critical drop height corresponding to a particular ball is known. In addition, this type of experiment provides us with a possible valuation of the thermodynamic work of adhesion (Dupre's energy of adhesion) and also allows us to determine the viscoelastic behaviour of the rubber-like material tested.