A FLEXIBLE BOUNDARY FOR 3-DIMENSIONAL DEM PARTICLE ASSEMBLIES

An algorithm is presented for creating a flexible boundary to analyze three-dimensional assemblies of spheres. It can be used to study localization phenomena in particulate materials. The boundary is composed of adjoining triangular plate elements which are connected at their corners to the centres of neighbouring spheres. The applied external boundary stresses create traction forces on the plates, which are distributed among the plates' particles. The boundary performed favourably in tests on a large assembly of particles when only contact and rotational damping were used. Plane strain compression tests on assemblies with flexible and periodic boundaries revealed a lower strength with the former. This result could be due to the greater restraint on particle movements produced by periodic boundaries or to the early development of a column buckling failure pattern of the assembly with flexible boundaries. No shear bands were observed in the assembly.