Impact deformation and rebound of wet granules

The impact behaviour of wet granules was studied by measuring their restitution coefficient and maximum contact area. A flat semi-infinite rigid target was used for this purpose and the impact and rebound speeds were recorded by using two high-speed cameras. Different granules were produced by varying the liquid to solid ratio, primary particle size, binder viscosity and granulation time. The data were compared with existing analytical models, which were found to provide an approximate description. However, it is clear that real granular collisions may involve a significantly greater complexity and this will require the refinement of such models.