Statistical distribution of contact forces in packings of deformable spheres

The probability distributions of contact forces in packings of polystyrene spheres are experimentally measured. The force distribution is found to be independent of the sphere size and the applied load, but is a strong function of the packing structure. The force distribution function transforms from a monotonically decreasing form to a peaked form as the packing structure changes from a random to a hexagonal-close-packed morphology. The force distributions in both cases can be described accurately by the same family of theoretical curves predicted by a theory based on statistical physics concepts.