Jump rule for edge impacts of rolling prisms

•The experiments for prisms purely rolling down a rough ramp exhibited several intriguing phenomena, such as the independence of the rolling speed on material, and the significance of the prism's geometry on the motion.•The edge impact is modeled with the consideration for the so-called detachment front propagating across the contact interface.•A scale number is found for characterizing the detachment front propagation involved in the edge impact.•A jump rule responsible for the response of an edge impact is successfully derived and it can be validated by the experiments. We study experimentally and theoretically the planar dynamics of purely rolling prisms on a rough ramp, where the rolling motion is interrupted intermittently by edge impacts. The experiments were carried out for prisms made of different materials and having different geometries. We found that the angular velocities of the rolling prisms are material-independent, but they change significantly with their geometry. We modelled the dynamics of edge impacts by considering a so-called detachment front propagating across the contact interface. The detachment front represents the moving boundary between a detached region and a stress region that coexist within the interface plane. The theoretical analysis indicates that the detachment front can be characterized by a scale number, whose value converges to 0.4050 for prisms having large number of edges. A new jump rule for edge impacts is then developed, by which we can accurately reproduce the experimental observations, and explain why the motion of the prism is material-independent.