We have recently developed some simple continuum models of static granular media which display “fragile” behaviour: they predict that the medium is unable to support certain types of infinitesimal load (which we call “incompatible” loads) without plastic rearrangement. We argue that a fragile description may be appropriate when the mechanical integrity of the medium arises adaptively, in respon...

We have found that the ability of long thin rods to jam into a solidlike state in response to a local perturbation depends upon both the particle aspect ratio and the container size. The dynamic phase diagram in this parameter space reveals a broad transition region separating granular stick-slip and solidlike behavior. In this transition region the pile displays both solid and stick-slip behav...

A model for granular material is presented that describes both the internal deformation of each granule and the interactions between grains. The model, which is based on the FLIP-Material Point, particle-in-cell method, solves continuum constitutive models for each grain. Interactions between grains are calculated with a contact algorithm that forbids interpenetration, but allows separation and...

We present an experimental investigation of the statistical properties of spherical granular particles on an inclined plane that are excited by an oscillating side wall. The data is obtained by high-speed imaging and particle tracking techniques. We identify all particles in the system and link their positions to form trajectories over long times. Thus, we identify particle collisions to measur...

Experiments on continuously sheared granular materials (glass spheres) with diameters 1.0 # d # 5 mm show large fluctuations in the normal stress, sstd. Experiments are carried out in an annular Couette geometry for rotation rates 0.003 , Ù u , 1 radys. Power spectra from sstd, Psvd, show rate invariance in the fluctuations: Ù uPsvd is a function only of vy Ù u, independent of Ù u. Ù uPsvd depe...

We examine the 'transmissibility' of a simulated two-dimensional pack of frictionless disks formed by confining dilute disks in a shrinking, periodic box to the point of mechanical stability. Two opposite boundaries are then removed, thus allowing a set of free motions. Small free displacements on one boundary then induce proportional displacements on the opposite boundary. Transmissibility is ...

A joint research project including Oryx Simulations AB and VRLab at Ume̊a University aims to create real-time simulations of “complex materials”, including granular materials such as sand and gravel. A study of existing methods for rendering results from particle based simulations of granular materials has been performed. A general approach, based on the marching cubes surface extraction algorit...

Based on numerical simulations of quasistatic deformation of model granular materials, two rheological regimes are distinguished, according to whether macroscopic strains merely reflect microscopic material strains within the grains in their contact regions (type I strains), or result from instabilities and contact network rearrangements at the microscopic level (type II strains). We discuss th...

We study the effects of long-range interactions on the phases observed in cohesive granular materials. At high vibration amplitudes, a gas of magnetized particles is observed with velocity distributions similar to nonmagnetized particles. Below a transition temperature compact clusters are observed to form and coexist with single particles. The cluster growth rate is consistent with a classical...