InteractionPossibilities of Bonded and Loose Particles in LS-DYNA®

The goal of this presentation is to outline the current development status of LS-DYNA® with respect to simulations using the discrete-element method (DEM), which is based on Cundall & Strack [1]. Starting with assemblies of loose discrete spherical particles, different types of granular media can be discretized to predict their behavior, for instance, during mixing processes, storage and discharge in silos or transportation on belts. Following this, the interaction of the discrete particles with themselves as well as their surrounding deformable or rigid structures can be taken into account. Herein, friction coefficients as well as spring and damping constants can be defined in normal and tangential direction. Wet particles can be estimated with the aid of a capillary force model. Even though the geometric shape of the particles is always spherical, a certain roughness of the grains can be achieved by introducing a rolling friction or by defining clustered particles using bonds. Moreover, with the introduction of bonded particles, linear-elastic solid material behavior can be modeled. Herein, the mechanical behavior of the bonds may either be prescribed manually or computed internally by LS-DYNA in an automated fashion using the elastic constants given in a material card. With the definition of a fracture energy release rate of the bonds, fracture mechanics of brittle materials can be studied. Herein, the number of bonds of a particle to the neighboring particles can be defined with a bond radius. Note that the breakage of single bonds can be interpreted as micro cracks that eventually evolve to macro cracks. This presentation will give an overview of the involved material cards and provides information on how the cards are used. For a better understanding of the involved parameters, simple examples will be presented addressing particle-particle as well as particle-structure interaction.