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 local ization phenomena in particulate materials. The boundary is composed o f adjoining triangular plate elements which are connected at their cor ners to the centres of neighbouring spheres. The applied external boun dary stresses create traction forces on the plates, which are distribu ted among the plates' particles. The boundary performed favourably in tests on a large assembly of particles when only contact and rotationa l damping were used. Plane strain compression tests on assemblies with flexible and periodic boundaries revealed a lower strength with the f ormer. This result could be due to the greater restraint on particle m ovements produced by periodic boundaries or to the early development o f a column buckling failure pattern of the assembly with flexible boun daries. No shear bands were observed in the assembly.