Conceptual experiments and discrete element simulations with polygonal particles

In the present work intentionally polygonal particles with a regular hexagonal geometry are investigated. This allows removing the complexity of randomly shaped particles thus concentrating on the interaction between adjacent particles. For this purpose, conceptual compression experiments on assemblies of hexagonal steel nuts are performed and subsequently simulated by a discrete element method. The interaction models for contact of two particles are as follows: in normal direction an elastic model augmented by a viscous supplement and in tangential direction an elasto-plastic model are applied; furthermore, an elasto-plastic model describes the contact of a particle with a plane underground. For an adhering bond between particles an elasto-damage beam including an axial force is introduced between the centers of adjacent particles. It allows modeling gradual failure of the bond. In order to test the capability of these models in a direct way, the conceptual experiments on simple regular particle arrangements are compared with their corresponding simulations. For samples of unglued particles relevant characteristics like shear bands are reproduced. For assemblies of particles glued together by an adhesive the study describes important failure properties like localization in cracks as well as ductile failure.