Introduction to Discrete Element Methods: Basics of Contact Force Models

One challenge of today's research is the realistic simulation of granular materials, like sand or powders, consisting of millions of particles. In this article, the discrete element method (DEM), as based on molecular dynamics methods, is introduced. Contact models are at the physical basis of DEM. A set of the most basic force models is presented involving either elasto-plasticity, adhesion, viscosity, static and dynamic friction as well as rolling- and torsion-resistance. The examples given concern clustering in granular gases, and bi-axial as well as cylindrical shearing of dense packings in order to illustrate the micro-macro transition towards continuum theory.