Effect of packing characteristics on the simulation of elasticity and brittle fracture by the Cohesive Discrete Element Method

The paper investigates the effect of packing characteristics on the simulation of elasticity and brittle fracture by the Cohesive Discrete Element Method. In such an approach, an effective elastic medium is modeled by a very dense granular system in which the cohesion is introduced at the scale of the elementary contact using a classical beam element. Typically, microscopic-macroscopic relations have to be set up to connect beam parameters to elastic coefficients but these are known to be very sensitive to the arrangement of particles. Our objectives in the present contribution are twofold. We first intend to determine the influence of main characteristics, namely the cardinal number, i.e. the average number of particles in contact with a given one, and the volume fraction of particles on the elastic response. For that purpose, numerical calculations are carried out on a large range of configurations using a specific process based on cubic representative patterns. Outputs exhibit a good agreement with analytical trends predicted by Voigt and best-fit hypotheses under some conditions related to the thickness of the beam. In a second part, typical diametral compression and quasi-static indentation tests are set up to explore the effect of the cardinal number on the brittle fracture of homogeneous media. Results show that a low coordination leads to unsuitable cracks initiation and propagation in some cases.