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...

The particle-scale dynamics of granular materials have commonly been characterized by the self-diffusion coefficient D. However, this measure discards the collective and topological information known to be an important characteristic of particle trajectories in dense systems. Direct measurement of the entanglement of particle space–time trajectories can be obtained via the topological braid ent...

The influence of periodic vibrations on the granular flow of materials is of great interests to scientists and engineers due to both theoretical and practical reasons. In this paper, the stability of a vertically vibrated granular layer is examined by linear stability analysis. This includes two major steps, firstly, the base state at various values of mass holdup (Mt) and energy input (Qt) is ...

We study strain localization in slow shear flow focusing on layered granular materials. A heretofore unknown effect is presented here. We show that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirme...

One challenge of todays research on particle systems is the realistic simulation of granular materials consisting of many thousands of particles with peculiar contact interactions. In this study, molecular dynamics (MD, also called discrete element method, DEM) is introduced for the simulation of many-particle systems. A wide class of realistic contact models is presented, involving dissipation...

Bulk density is an important process parameter for machines that transport, feed or process granular materials. Certain process variables have been shown to increase bulk density, such as the channel geometry at machines with rotational helical elements, the shape, dimensions and dimension distribution of granules, pressure, temperature, and vibration of the granular layer. The effect of the ra...