Evolution of a contact force network in a 2D granular assembly: an examination using neutron diffraction.

Results from an experiment involving the measurement of individual particle stresses in a two-dimensional mono-disperse assembly of 579 ball bearings are presented. Using a combination of neutron radiography and strain scanning techniques, the full bi-axial stress state was obtained for each particle from which the full contact force network could be established. The evolution of this network was examined over a series of five monotonically increasing loads. Significant levels of inhomogeneity were observed in the form of prominent force chains that showed complex interaction with regions of order and disorder within the assembly. A reduction in the level of inhomogeneity with increasing load was also observed. [ABSTRACT FROM AUTHOR]