Force chains and contact network topology in sheared packings of elongated particles

Abstract

By means of contact dynamic simulations, we investigate the contact network topology and force chains in two-dimensional packings of elongated particles modeled by rounded-cap rectangles. The morphology of large packings of elongated particles in quasistatic equilibrium is complex due to the combined effects of local nematic ordering of the particles and orientations of contacts between particles. We show that particle elongation affects force distributions and force/fabric anisotropy via various local structures allowed by steric exclusions and the requirement of force balance. As a result, the force distributions become increasingly broader as particles become more elongated. Interestingly, the weak force network transforms from a passive stabilizing agent with respect to strong force chains to an active force-transmitting network for the whole system. The strongest force chains are carried by side/side contacts oriented along the principal stress direction.

Particle alignment and clustering in sheared granular materials composed of platy particles

“…The increase of these interactions has also been observed in experiments [42] as well as in numerical simulations with elongated particles in 2D [15,18].…”

“…Due to dynamics in continuous shearing, this ordering phenomenon emerges even in systems composed of particles with very low platyness with a shape differing only slightly from spherical shape. This kind of ordering has previously been observed in experiments [27,22] and numerical simulations mainly with two-dimensional elongated particles [28,15,18]. Regarding the privileged direction of alignment, we found that, as platyness increases, this direction gradually changes from that of the major principal stress to a direction that is perpendicular to the shear direction.…”

“…The contact networks resulting from various shapes appear to be highly complex and hardly amenable to simple statistical modeling. For example, face/face interactions are critical for polyhedra whereas interlocking of the particles is important in the case of non-convex shapes [15,21,16,18,19]. In the same way, nematic order appears in packings of elongated particles [10][11][12]9,15,18].…”

“…Oblate particles prefer facing along the major principal stress direction with the flat side, while prolate particles prefer orientation of their long axis along the minor principal stress direction [23][24][25][26][27][28]. It is also shown that, with increasing particle aspect ratio, the weak force network transforms from a passive stabilizing agent with respect to strong force chains to an active force-transmitting network for the whole system [18].…”

Bonded-cell model for particle fracture

“…In CD, an iterative algorithm based on nonlinear Gauss-Seidel iterations is used to determine the contact forces and particle velocities simultaneously at all potential contacts. The CD method has been extensively employed for the simulation of granular materials in 2D and 3D [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72].…”