Numerical analysis of the vibrated packing densification of binary equilateral cylindrical particle mixtures

In this work, the packing densification of binary equilateral cylindrical particle mixtures under three-dimensional (3D) mechanical vibration was numerically simulated using the discrete element method. The influence of vibration conditions (vibration frequency f and amplitude A), size ratio r (diameter of large particles vs that of small particles), and composition XL% (volume fraction of large particles) on the packing density was systematically analyzed. Furthermore, the microscopic properties such as coordination number (CN), radial distribution function (RDF), contact types, forces, and stresses of the packing structures were characterized. The results demonstrate that the packing densification of binary equilateral cylindrical particles can be realized by properly controlling the vibration conditions. An appropriate composition (e.g., 70% volume fraction of large cylinders) combined with a large size ratio leads to a high packing density. The mean CN decreases to a minimum and then increases as XL% increases. A larger size ratio corresponds to a smaller mean CN. Analysis of the contact types and RDF demonstrates that the packing structures of binary cylindrical particle mixtures are dominated by large and small particle contacts. The distributions of strong stresses follow an exponential law. Mean stress analysis indicates that large particles play a crucial role in supporting the applied load in binary packings. The results of this work are helpful for understanding the binary packing of non-spherical particles.