Granular simulations with LAMMPS: enhanced contact models and applications to powder rheology

We discuss recent additions to the LAMMPS granular pair styles, including cohesion, rolling and twisting friction, and the ability to set different parameters for different particle types. These capabilities are applied to simulations of powders, where individual powder particles take the place of atoms in a traditional molecular dynamics context. We aim to understand flow characteristics of powders through a wide range of simulations that are compared to experiments, including triaxial compression tests, powder rheometry and funnel flow. The driving application is a modeling capability for powder handling aspects of metal additive manufacturing processes, but more generally, we aim to provide a link between fundamental particle properties, such as particle size distribution, friction, cohesion, etc., and bulk flow behavior as measured by a range of powder flow index tests.