Effect of particle size ratio and contribution of particle size fractions on micromechanics of uniaxially compressed binary sphere mixtures

Abstract

This paper is an extension of the recent work of Wiącek (Granul Matter 18:42, 2016), wherein geometrical parameters of binary granular mixtures with various particle size ratio and contribution of the particle size fractions were investigated. In this study, a micromechanics of binary mixtures with various ratio of the diameter of small and large spheres and contribution of small particles was analyzed using discrete element simulations of confined uniaxial compression. The study addressed contact normal orientation distributions, global and partial contact force distributions and pressure distribution in packings of frictional spheres. Additionally, the effect of particle size ratio and contribution of particle size fractions on energy dissipation in granular mixtures was investigated. The particle size ratio in binary packings was chosen to prevent small particles from percolating through bedding. The bimodality of mixtures was found to have a strong effect on distribution of contact normal orientation and distribution of normal contact forces in binary mixtures. Stress transfer in binary packing was also determined by both, particle size ratio and volume fraction of small particles. Dissipation of energy was higher in mixtures with higher particle size ratios and decreased with increasing contribution of small spheres in system.

Effect of the particle size ratio on the structural properties of granular mixtures with discrete particle size distribution

“…Heterogeneous distributions of contact angles with a preference for the vertical and horizontal directions were observed in monodisperse samples, in which ordered structures were formed by uniformly sized particles. The prevalence of contact normals directed vertically and horizontally was also observed in binary packings, that increased with increasing g. In all packings with g = 1.25, in which particles were arranged in a nearly crystalline formation, the vertical contact direction prevailed and degree of contact orientation anisotropy changed slightly with increasing n. For samples with g > 1.25, degree of anisotropy in the distribution of contact angles decreased with increasing n. These finding agree with those of Wiącek and Molenda [12] for polydisperse samples with continuous PSDs and the results of Wiącek et al [19] for binary granular packings.…”

“…The mechanical properties and compaction characteristics of polydisperse materials have been extensively studied because, in granular systems, particle rearrangement and contact networks are determined by the degree of heterogeneity in particle size [12,19]. Wiącek et al [19] numerically studied the effect of particle size ratio on geometric anisotropy in binary sphere packings.…”

“…A higher number of particle size classes indicated a higher degree of complexity and makes interpreting the materials' characteristics more difficult. Numerous studies have focused on bimodal particulate beds, which are the simplest example of a polydisperse granular material [6,13,[16][17][18][19]21,22], along with systems composed of three or four particle size fractions [6,14,[23][24][25][26][27]. These studies provided valuable knowledge related to the structural and mechanical properties of polydisperse granular materials.…”

Structural and Micromechanical Properties of Ternary Granular Packings: Effect of Particle Size Ratio and Number Fraction of Particle Size Classes

“…The composition of multi-sized mixtures, determining packing density and distribution of contacts in granular assemblies, also has great influence on their mechanical properties. Micromechanical properties (e.g., distribution of normal contact forces, stress transmission, mobilisation of friction at contact points) and macromechanical properties (e.g., flowability, permeability, elasticity and strength) of granular packings were both found to be affected by degree of particle size heterogeneity and volume fraction of particle size classes [17][18][19][20][21].…”

Computational domain discretization in numerical analysis of forced convective heat transfer within packed beds of granular materials

“…Packed beds of granular materials are the focus of numerous experimental and theoretical studies due to their widespread prevalence in nature and common application in industry (Hu et al, 2017;Oschmann and Kruggel-Emden, 2017;Więcek, Parafiniuk and Stasiak, 2017;Krzywanski et al, 2017).…”