Detachment of glass balls from smooth rubber under gravity

In numerous previous experiments for 30 years, we have studied, as much other scientists, especially the group of the English School, the kinetics of adherence of various rigid transparent punches in contact with the plane and smooth surface of a rubber–like material, by measuring the evolution of the radius of contact area when a tensile force is imposed to separate the two bodies. Here, we propose a simple method to predict the kinetics of detachment of several balls submitted to their own weights, i.e. the duration necessary to observe the rupture of contact, when it is impossible to measure the area of contact because the bodies are not transparent, for instance. This method only assumes the knowledge of the dissipation function versus the crack propagation speed at the interface between the rubber sample and the rigid body in contact.