A Granular System of Ellipses under Linear Shear

¹ Department of Physics & Center for Nonlinear and Complex System, Duke University, Durham, NC, USA
² School of Earth Science and Engineering, Hohai University, Nanjing 210098, China

^* e-mail: dw148@duke.edu
^** e-mail: hz64@phy.duke.edu
^*** e-mail: bob@phy.duke.edu

Published online: 30 June 2017

Abstract

Shear of granular systems of disks (in 2D) and spheres (3D) has been studied extensively. However, less is known about systems of non-spherical particles, i.e., ellipses and polygons, etc. Here we studied a quasi 2D granular system composed of ellipses in a novel apparatus, which provided homogeneous simple shear by utilizing the weak friction between ellipses and the deformable base of the apparatus. Shear jamming, which was first reported for a disk system [1], was also observed for our ellipse system. We contrast shear jamming for systems of disks and systems of ellipses. By tracking the positions and orientations of the ellipses, we observed that the ellipses gradually rotated to align along a preferred direction as the shear strain increased. We also applied Voronoï tessellation to the packing of ellipses, showing that the distribution of the local density changed during shear. By contrast, such a change in the distribution was not observed in a disk system [2].