Large-scale deformation processes and mechanisms of the model aggregates comprising close-packed spherical particles are examined by the use of a discrete element method (DEM). It is demonstrated that the movement of grain groups, i.e., the cooperative grain-boundary sliding (CGBS), is essential in the large-scale elongation of polycrystalline materials. The strain energy of grain aggregates during CGBS is also estimated as a function of true strain, yielding a good agreement with the theoretical prediction of CGBS process. The discrete element analysis used in this study is an efficient technique in examining the large-scale deformation mechanism such as the superplastic deformation of polycrystalline materials.
