PARTICLES 2023

2D DEM Study of Force Transmission in Flexible Granular Chain Packings

  • Bhat, Mohd Ilyas (Indian Institute of Science, Bangalore)
  • Murthy, Tejas G (Indian Institute of Science, Bangalore)

Please login to view abstract download link

Flexible granular chains form an exciting class of elasto-granular materials, wherein the inclusion of tension-transmitting elements enhances the mechanical properties of a cohesionless granular material (Fig. 1). These chains exhibit an array of intriguing properties such as jamming at low packing density, strain stiffening, higher stiffness at small coordination numbers. Unlike other cohesionless granular materials, which flow and form conical piles on repose, the packing of these chains entangles and forms stable standing vertical columns (Sarate et al., 2022). This flow behaviour makes studying force transmission and wall pressures in these chain packings an exciting problem to explore. Although experimental measurements have provided insight into the ensemble-level static behaviour of these chain packings, much is yet to be explored about their particle-level micromechanics. We explore the static pressure distributions in 2D random chain packings and contrast their behaviour with the Janssen effect observed in conventional cohesionless granular materials. Numerical methods such as Monte Carlo and molecular dynamics have been employed to study the particle-level mechanics of flexible granular chains. However, most of these studies have been carried out for drastically different length scales of molecular polymer melts. In our DEM contact model, the links connecting the beads in the chains are implemented as a combination of a linear normal and angular stiffness, which constrains the inter-particle elongation and the bending angle between three consecutive beads. (Fig. 1). We generate 2D chain packings in a vertical cylinder with varying chain length (M), friction coefficients (μs,μr), column height (H0), container size (R/r) and deposition methods. Apart from the wall forces, we evaluate various micro-mechanical, topological and macroscopic parameters to elucidate the micro-mechanical response of these packings. The ability of the chains to form tensile force chains affects the saturation of the column base pressure. Moreover, the flexible geometry of the chains results in the formation of chain loops, leading to larger heterogeneity and anisotropy in contact force chains.