Contact models for very loose granular materials

One challenge of todays research on particle systems is the realistic simulation of granular materials consisting of many thousands of particles with peculiar contact interactions. In this study, molecular dynamics (MD, also called discrete element method, DEM) is introduced for the simulation of many-particle systems. A wide class of realistic contact models is presented, involving dissipation, adhesion, plastic deformation, friction, rollingand torsion resistance. The effect of the contact properties on a simple compaction test is discussed with the goal to achieve as small as possible packing densities. With contact forces only, packing volume fractions down to 0.42 can be achieved, while somewhat longer ranged adhesion forces allow for volume fractions as low as 0.34.