Low-Frequency Behavior of Beads Constrained on a Lattice

Bruno Gilles (1) , Christophe Coste (2)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 MSC - Matière et Systèmes Complexes

We study sound propagation in a triangular lattice of spherical beads under isotropic stress. Polydispersity of real beads breaks some contacts, creating a disordered lattice of contacting beads. At large stress, the sound velocity behaves according to Hertz contact law and departs from it at lower stress. This evolution is reversible, with the same crossover when increasing or decreasing the stress, for a given piling. Correlations are much more sensitive to disorder. When calculated with signals propagated in the same lattice, they evolve reversibly with the stress, being much higher at large stress when the contact lattice is more regular. This leads to an interpretation of the non-Hertzian behavior in terms of progressive activation of contacts, in discrepancy with previous models involving buckling of force chains.

Domaines: Acoustique [physics.class-ph]

Bruno Gilles, Christophe Coste. Low-Frequency Behavior of Beads Constrained on a Lattice. Physical Review Letters, 2003, 90 (17), pp.174302. ⟨10.1103/PhysRevLett.90.174302⟩. ⟨hal-01406751⟩