Effect of Particle Shape on Stress-Strain Measurements of Granular Materials

ORAL

Abstract

Granular materials are composed of many discrete athermal particles, which exhibit liquid like properties below some critical packing fraction and solid like properties, such as yield stress, above. Physics research has generally considered granular materials composed of spherical grains. Most natural grains are not spherical, but rather odd shapes that often break symmetries and exhibit various contact modes. Therefore, in addition to circles, we study quasi-2D elliptical, pentagonal, and star-shaped particles. This set of particles were chosen to break rotational symmetry, introduces point-face and face-face contacts, and even interlock. We measure the yield stress as a function of packing fraction for each type of grains. Our experiment consists of 820 particles floating on an air table, compressed bi-axially. Utilizing force sensors along the walls and an overhead camera, we are able to determine the bulk pressure and the packing fraction. We find that the critical packing fraction is shape dependent. However, this shape dependence can be scaled out of the pressure versus packing fraction relation.

–

Authors

  • Sara Berry

    North Carolina State Univ

  • Brad Cox

    North Carolnia State University, Vanderbilt University, University of South Carolina, University of Virginia, Francis Marion Univ, Oak Ridge National Laboratory, Massachusetts Institute of Technology, Florida International University, Georgia College, JINR, Tsinghua University, LBNL, GANIL, Austin Peay State University, Lehigh University, University of Pardubice, Universit\'e de Rennes, Austin Peay State University Department of Physics and Astronomy, Oak Ridge National Laboratory, Oak Ridge TN 37831, American Superconductor Corp., Westborough MA 01581, University of North Georgia, Dahlonega GA 30597, Florida State University, Ecole Polytechnique, Space Telescope Science Institute, Fermi National Accelerator Lab, National Optical Astronomy Observatory, Austin Peay State Univerity, North Carolna State University, Florida Intl Univ, University of North Georgia, Clemson University, Clemson Univ, Vanderbilt University/ORNL, Vanderbilt University/Univ. of Kentucky, College of William and Mary, Louisiana State University, Presbyterian College, North Carolina State Univ, Department of Physics, Virginia Tech, Mathematical Institute, University of Oxford, Virginia Tech University, Hollins University, University of Tennessee Space Institute, Davidson College, University of Tennessee, American Superconductor Corporation, University of South Alabama, North Carolina State University, James Madison University, Lousiana State University, Korea Electrotechnology Research Institute, Changwon Korea

  • Brad Cox

    North Carolnia State University, Vanderbilt University, University of South Carolina, University of Virginia, Francis Marion Univ, Oak Ridge National Laboratory, Massachusetts Institute of Technology, Florida International University, Georgia College, JINR, Tsinghua University, LBNL, GANIL, Austin Peay State University, Lehigh University, University of Pardubice, Universit\'e de Rennes, Austin Peay State University Department of Physics and Astronomy, Oak Ridge National Laboratory, Oak Ridge TN 37831, American Superconductor Corp., Westborough MA 01581, University of North Georgia, Dahlonega GA 30597, Florida State University, Ecole Polytechnique, Space Telescope Science Institute, Fermi National Accelerator Lab, National Optical Astronomy Observatory, Austin Peay State Univerity, North Carolna State University, Florida Intl Univ, University of North Georgia, Clemson University, Clemson Univ, Vanderbilt University/ORNL, Vanderbilt University/Univ. of Kentucky, College of William and Mary, Louisiana State University, Presbyterian College, North Carolina State Univ, Department of Physics, Virginia Tech, Mathematical Institute, University of Oxford, Virginia Tech University, Hollins University, University of Tennessee Space Institute, Davidson College, University of Tennessee, American Superconductor Corporation, University of South Alabama, North Carolina State University, James Madison University, Lousiana State University, Korea Electrotechnology Research Institute, Changwon Korea