Résumé
By means of particle dynamics simulations, we investigate the elastic moduli of dense packingsof spherical and dodecahedral monodisperse particles. The samples are prepared by isotropiccompaction under constant load and zero friction, leading to the densest isotropic state, which isunique for each particle type. Then, they are subjected to quasi-static triaxial compression usingtri-periodic boundary conditions, thereby removing spurious wall effects, for different values of theinterparticle friction coefficient (from 0.1 to 0.4). From the stress and strain data, we evaluate theeffective elastic moduli (the Young modulus, bulk modulus and Poisson ratio) at several instancesof deformation by applying shear reversal. We find that the elastic moduli are independent of thefriction coefficient at very small shear deformations due to the stability of the contact network atsuch dense states, but undergo considerable change at larger deformations when interparticlecontacts begin to slide or are lost along the direction of extension. Notably, beyond this point theYoung modulus declines with further deformation to a value all the more small that the friction co-efficient is larger. In all cases, the bulk modulus increases with deformation. The shear modulusis found to be larger for polyhedral particles due to stronger constraints on particle movements.Our data show that the initial Poisson ratio is 0.12 for spherical particle packings, in agreementwith those of Agnolin and Roux [1], and 0.09 for packings of rigid polyhedral particles. This lowervalue of the Poisson ratio reflects the lower mobility of the particles.