Proceedings Issue: Behavior of Granular Media (2006) About contact force-laws for cohesive frictional materials in 2D and 3D

Ultrafine, cohesive powders are the subject of the joint research project. While shear experi-ments and contact force measurements were performed by the project partners, the realistic contact force models were developed in a common effort. The algorithms for their implementation are pre-sented here, involving elastic-plastic repulsion, dissipation, adhesion, friction as well as rolling- and torsion-resistance. In model powder systems, the effect of the contact properties on an isotropic, homogeneous com-paction test is discussed with respect to the packing densities. With contact forces involving sliding, rolling and torsion frictions, packing volume fractions down to 0.42 were achieved. Some longer ranged van der Waals adhesion forces added to the contact forces can lead to volume fractions con-siderably smaller, and to fractal-like agglomerates. Keywords granular materials, molecular dynamics (MD) and discrete element model (DEM) force-laws, fric-tion, rolling- and torsion resistance, adhesion, plastic deformation, low density compaction