Structural signature of jamming in granular media

Abstract

Glasses are rigid, but flow when the temperature is increased. Similarly, granular materials are rigid, but become unjammed and flow if sufficient shear stress is applied. The rigid and flowing phases are strikingly different, yet measurements reveal that the structures of glass and liquid are virtually indistinguishable. It is therefore natural to ask whether there is a structural signature of the jammed granular state that distinguishes it from its flowing counterpart. Here we find evidence for such a signature, by measuring the contact-force distribution between particles during shearing. Because the forces are sensitive to minute variations in particle position, the distribution of forces can serve as a microscope with which to observe correlations in the positions of nearest neighbours. We find a qualitative change in the force distribution at the onset of jamming. If, as has been proposed, the jamming and glass transitions are related, our observation of a structural signature associated with jamming hints at the existence of a similar structural difference at the glass transition--presumably too subtle for conventional scattering techniques to uncover. Our measurements also provide a determination of a granular temperature that is the counterpart in granular systems to the glass-transition temperature in liquids.

Force analysis of clogging arches in a silo

“…For the bulk, we obtain the typical monotonous exponential decay that is often observed in granular materials. On the contrary, the force distribution in the arch exhibits a narrower distribution with a maximum that has been typically attributed to the development of yield stress and force chains [36][37][38][39]. Indeed, it is expected that in arches, the values of forces lie around the average as the forces acting on a particle must be compensated.…”

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

“…Due to its great importance in many fields the unique characteristics of the jammed state have been studied extensively over the last years (Ballesta et al, 2008;Corwin et al, 2005;Donev et al, 2004aDonev et al, , 2004bDonev et al, , 2005aGoodrich et al, 2012;Keys et al, 2007;Lu et al, 2008;O'Hern et al, 2002O'Hern et al, , 2003Zexin et al, 2009). While initial studies focused understandably on dense packing of uniform spheres research has since been extended to objects with complex, anisotropic shapes (Donev et al, 2006;Frenkel et al, 1988;Haji-Akbari et al, 2013, 2011a, 2011bJiao et al, 2009;Jiao and Torquato, 2011;Torquato and Jiao, 2009;Veerman and Frenkel, 1991;Xu et al, 2005;Zeravcic et al, 2009).…”

Force statistics and correlations in dense granular packings

“…Furthermore, it is observed that the deformation of particle systems is not affine in general, but displays finite distance correlations which are assumed to increase when approaching the jamming transition [6,19,20,21,22,23,24,25,26,27]. However, the issue whether these correlations (and possibly anticorrelations due to vortex formation) depend on the system size [28] or not [29,30] is not completely resolved yet.…”