title: Internal friction and absence of dilatancy of packings of frictionless polygons.
abstract: By means of numerical simulations, we show that assemblies of frictionless rigid pentagons in slow shear flow possess an internal friction coefficient (equal to 0.183±0.008 with our choice of moderately polydisperse grains) but no macroscopic dilatancy. In other words, despite side-side contacts tending to hinder relative particle rotations, the solid fraction under quasistatic shear coincides with that of isotropic random close packings of pentagonal particles. Properties of polygonal grains are thus similar to those of disks in that respect. We argue that continuous reshuffling of the force-bearing network leads to frequent collapsing events at the microscale, thereby causing the macroscopic dilatancy to vanish. Despite such rearrangements, the shear flow favors an anisotropic structure that is at the origin of the ability of the system to sustain shear stress.
authors: Université de Montpellier, CNRS, LMGC, Cc 048, Place Eugène Bataillon, F-34095 Montpellier cedex 05, France.
authors: Émilien
authors: É
authors: Azéma
authors: Université de Montpellier, CNRS, LMGC, Cc 048, Place Eugène Bataillon, F-34095 Montpellier cedex 05, France and MIST, CNRS-IRSN, Université de Montpellier, France and 〈MSE〉2, UMI 3466 CNRS-MIT, CEE, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Farhang
authors: F
authors: Radjaï
authors: Université Paris-Est, Laboratoire Navier, 2 Allée Kepler, Cité Descartes, 77420 Champs-sur-Marne, France.
authors: Jean-Noël
authors: JN
authors: Roux