Jamming transition in non-spherical particle systems: pentagons versus disks

Abstract

We investigate the jamming transition in a quasi-2D granular material composed of regular pentagons or disks subjected to quasistatic uniaxial compression. We report six major findings based on experiments with monodisperse photoelastic particles with static friction coefficient µ ≈ 1. (1) For both pentagons and disks, the onset of rigidity occurs when the average coordination number of non-rattlers, Z nr , reaches 3, and the dependence of Z nr on the packing fraction φ changes again when Z nr reaches 4. (2) Though the packing fractions φ c1 and φ c2 at these transitions differ from run to run, for both shapes the data from all runs with different initial configurations collapses when plotted as a function of the non-rattler fraction. (3) The averaged values of φ c1 and φ c2 for pentagons are around 1% smaller than those for disks. (4) Both jammed pentagons and disks show Gamma distribution of the Voronoi cell area with same parameters. (5) The jammed pentagons have similar translational order for particle centers but slightly less orientational order for contacting pairs compared to jammed disks. (6) For jammed pentagons, the angle between edges at a face-to-vertex contact point shows a uniform distribution and the size of a cluster connected by face-to-face contacts shows a power-law distribution.

Structured randomness: jamming of soft discs and pins

“…Over two decades ago, it was first proposed [1][2][3] that soft and granular materials can have a jammed, solid phase, which forms at sufficiently high packing fraction or pressure, and sufficiently low shear and temperature. Now, much is known about materials in the vicinity of the zero-temperature jamming threshold, ''Point J''; not only for simple models like soft or hard repulsive, frictionless spheres, [4][5][6][7] but for particles which are non-spherical, [8][9][10][11][12] have rough and/or frictional surfaces, 13,14 are confined within various wall geometries [15][16][17] and even active matter [18][19][20] (including work on active matter in the presence of fixed obstacles 21 ). For frictionless soft spheres, a mixed firstsecond order phase transition, with upper critical dimension of d = 2 occurs 6,[22][23][24] at a maximally random close packing fraction (MRP).…”

Particle dynamics in two-dimensional point-loaded granular media composed of circular or pentagonal grains

“…As demonstrated in Fig. 1, the intruder leaves a channel in its wake as it pushes through the system; local packing fractions outside of the channel and for a stable cluster of grains in front of the intruder are significantly closer to the expected frictional jamming fraction ∼ 0.78 [15]. The difference between the global packing fractions for disks and pentagons can thus be largely attributed to the fact that the size of the cluster of particles in front of the intruder is significantly smaller for pentagons than for disks.…”

“…Recent studies of granular media composed of grains of a variety of shapes have shown that non-spherical/noncircular grains, which feature additional rotational resistance at the grain-grain interaction scale [9] , better represent measurable bulk parameters like shear strength [10][11][12][13], relative viscosity [14] in sheared suspensions, and jamming packing fraction [15] observed in real systems.…”

A Modeling Framework for Jamming Structures

“…Interlocking geometries can be utilized to create kinematic constraints to only allow for motion in particular directions. [ 31–35,53–57 ] Fibers can have prismatic cross sections, rather than circular ones to avoid kinematic rearrangement in particular directions and to transform the contact lines between constituents into contact surfaces. [ 14 ] Particles can be designed with particular geometries to create larger number of contact points, or larger contact surface areas between the particles.…”