Force correlations, anisotropy, and friction mobilization in granular assemblies under uniaxial deformation

Abstract

Abstract. We study dense, frictional, polydisperse 3D granular assemblies under uniaxial deformation with Discrete Element Method (DEM) simulations. The overall goal -beyond the scope of the present study -is to link microscopic parameters and observations with the macroscopic behavior, for different elementary deformation modes.At present, we focus on the behavior of the force/contact network during uniaxial deformation, for different coefficients of friction. We discuss the stress and structural anisotropy and the relationship between force intensity weighted by contact state (sticking or sliding, at the Coulomb limit) or force strength. Furthermore, we study the orientational distribution of contacts and forces and the contribution of friction to structural anisotropy. We find that initial isotropic states are irrecoverable, since the structural anisotropy is independent of the deviatoric stress behavior both with and without friction. Contacts display an interesting anisotropy of order four in the presence of friction.

Micro-macro correlations and anisotropy in granular assemblies under uniaxial loading and unloading

“…where T i 's are eigenvalues of T . Also, T (1) D , T (2) D , and T (3) D are the eigenvalues sorted such that, as convention, T (1) D T (2) D T (3) D . R = (n 1 ,n 2 ,n 3 ) is the orthogonal transformation matrix, composed of the corresponding eigenvectors, which transforms T D to its eigensystem.…”

“…J 3 can further be written as J 3 = T (1) D T (2) D (−T (1) D − T (2) D ), since we are dealing with deviators.…”

“…Granular materials are omnipresent in nature and widely used in various industries such as food, pharmaceutical, agriculture, and mining, among others. In many granular systems, interesting phenomena like dilatancy, anisotropy, shear-band localization, history dependence, jamming, and yield have attracted significant scientific interest over the past decade [1][2][3]. The bulk behavior of these materials depends on the behavior of their constituents (particles) interacting through contact forces.…”

Slow stress relaxation behavior of cohesive powders

“…Granular materials are omnipresent in nature and widely used in various industries ranging from food, pharmaceutical, agriculture and mining -among others. In many granular systems interesting phenomena like dilatancy, anisotropy, shear-band localization, history-dependence, jamming and yield have attracted significant scientific interest over the past decade ; Imole et al (2013b); Alonso-Marroquin and Herrmann (2004). The bulk behavior of these materials depends on the behavior of their constituents (particles) interacting through contact forces.…”

Micro-macro and jamming transition of polydisperse granular materials

“…This indicates that more new contacts are created in the axial direction compared to the perpendicular isotropic plane at the beginning of the loading path. At higher deviatoric strain [85], the fabric behavior becomes opposite and now more new contacts are created in the horizontal direction rather then in the vertical one, where most available neighbors already have come into contact. The 'softening' in deviatoric fabric does not correspond to any decrease in deviatoric stress that grows monotonically until saturation is reached (see Fig.…”