Experimental study on the packing of cubic particles under three-dimensional vibration

Densification of cubic particles under three-dimensional (3D) mechanical vibration was studied experimentally. Effects of vibration time (t), frequency (f), vibration amplitude (A), vibration acceleration (Gamma), container size (D) and particle sphericity (phi) on packing density (rho) were comprehensively analyzed. To identify the effects of particle shape, the packing densification of cuboid 1 (12 mm x 12 mm x 28 mm) and cuboid 2 (4 mm x 8 mm x 16 mm) were systematically studied under the same conditions. The results show that the structure of cubic particles can be first densified from random loose packing (RLP) to random close packing (RCP) and then to ordered packing (OP) gradually. In comparison, cuboid 1 and cuboid 2 particles can only form RCP structure, but cannot achieve OP even under further vibration. Vibration parameters (t; f, A and Gamma) are shown to be important to the packing densification. Based on the results of varying f and A, A - f phase diagrams are established for choosing the optimal vibration parameters to achieve the desired dense packing structures. Besides, it is shown the size of container (wall effect) has monotonic influence on packing density, i.e., the larger container size corresponds to the less wall effect and higher packing density. Cubic particles can form ordered packing because of the geometrical symmetry with aspect ratio of 1. After eliminating the wall effect by extrapolating the packing densities in different sized containers, typical packing densities of the three types of particles are obtained with rho(RLP) = 0.658, rho(RCP), = 0.830 and rho(OP) = 0.965 for cubic particles; rho(RLP) = 0.625 and rho(RCP) = 0.740 for cuboid 1 particles; rho(RLP) = 0.591 and rho(RCP) = 0.731 for cuboid 2 particles. These findings indicate cubic particles are efficient in densification which can be readily realized through proper 3D mechanical vibration. (C) 2017 Elsevier B.V. All rights reserved.