Interparticle force analysis on the packing of fine ellipsoids J.Q. Gan, Z.Y. Zhou ⁎, A.B. Yu Laboratory for Simulation and Modeling of Particulate Systems, Department of Chemical Engineering, Monash University, VIC 3800, Australia abstract article info Article history: Received 21 February 2017 Received in revised form 5 June 2017 Accepted 22 July 2017 Available online 25 July 2017 Particle size and shape are two important properties affecting the force structure in particle packings. By means of discrete element method, we investigate the force ratios, force network and force probability distribution in the three-dimensional packing of fine ellipsoids. The simulation results demonstrate that with particle size decreasing, the linear relationship between contact force ratio and bed depth fluctuates more significantly for ellipsoids. The force network for coarse particles demonstrates that the forces can propagate in long chains in the vertical direction for spheres; while they become more complex and zigzag for ellipsoids. Similar to spheres, exponential relationship also exists between porosity and inter-particle force ratio for ellipsoids, but it is also a function of particle shape. The probability distribution of contact force and total (normal) force are examined in details to quantify the force variation in the disordered packings of fine ellipsoidal particles. © 2017 Elsevier B.V. All rights reserved. Keywords: DEM Fine ellipsoid Packing Contact force Force network 1. Introduction Packings of fine powders of different size and shape pervade in many industries. A crucial property of the packings of granular materials is their heterogeneity. For spheres, it is generally agreed that large forces are carried by a network of preferred paths (so called “force chains”), while some grains carry only very small forces (so called “arching effect”). Force networks have attracted considerable attention in the past two decades as the distribution of interparticle forces is relevant to particle mechanical properties such as the fracture and crushing. Experimental measurements such as carbon paper [1,2], photoelastic materials [3] and confocal fluorescence microscopy techniques [4,5], and numerical experiments [6–8] are utilized to determine the proba- bility distribution of interparticle forces on coarse spherical packings. The general finding is that force distributions decay exponentially for large force, albeit with non-universal exponents (a Gaussian centre for sufficiently strong deformations [9]). Several features stand out with a peak near the mean force and a nonvanishing weight as force tending towards zero, which reflects heterogeneity in the force network. While there are numerous studies on the force distribution of coarse spheres where particle gravity is non-ignorable, only limited work is done for packings where cohesive interparticle forces are present and play a dominant role. The particle size with respect to interparticle force distribution was addressed by Yang et al. [10]. It revealed that with decreasing particle size, the normal contact forces become more uniform and have a narrower and more symmetric distribution; while the distributions of the total normal forces widen. The correlation be- tween force ratio and porosity was also established. This correlation was later found also applicable to the packing of fine spheres with electrical forces with the same parameters [11]. Particle shape is another major characteristic of granular material. Some work has been done on the force structure of coarse non- spherical particle packings. Guises et al. [12] demonstrated that the stress propagation may follow various patterns that results from com- plex interactions largely influenced by the grain shape. The 2D granular packing of elongated particles showed that the long force chain become more zigzag as particle elongation increases [13]. For 2D ellipse packing, the eccentricity of particles significantly influences the distribution of the stress and the contact forces. Zhu [14] showed that the peak load at- tenuation increases as the particle width is increased when maintaining the same particle mass or particle length. At low forces, however, the shape of the distribution of the contact forces is affected by particle geometry, and the probability distribution of contact force diverges from a strictly exponential distribution when aspect ratio is increased [12]. Azéma and Radjaï [15] investigated the contact network topology and force chains in 2D packings of elongated particles subjected to biaxial shearing, and found that the force distributions become increas- ingly broader as particles become more elongated. However, to the authors' best knowledge, little has been done on the force structure of packings of fine non-spherical particles. Many fundamental questions are not clear yet. For example, how do the interparticle forces evolve with particle size and shape? Can the force chain still be observed in the packings of fine non-spherical particles? Does the correlation between force ratio and porosity still exist for fine non-spherical particles? Powder Technology 320 (2017) 610–624 ⁎ Corresponding author. E-mail address: zongyan.zhou@monash.edu (Z.Y. Zhou). http://dx.doi.org/10.1016/j.powtec.2017.07.064 0032-5910/© 2017 Elsevier B.V. All rights reserved. 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