DEM simulation of random loose packings of micron-sized particles with both adhesion and friction

Abstract

Random loose packings of uniform spherical micron-sized particles are ully investigated by means of a 3D discrete-element method with adhesive contact mechanics. Characterized by a dimensionless adhesion parameter Ad = ω/(2ρpU20 R), the packing properties go back to RLP/RCP with Ad < 1 while a unique adhesion-controlled packing regime is obtained when Ad > 1. The asymptotic adhesive loose packing limit is approached as Ad > 20. Both the normal and tangential forces of these adhesive loose packings are measured and their distributions follow P(f) ~ fθ for small forces and P(f) ~ e−βf for big forces, respectively. Distinct exponents of θ = 0.879, β = 0.839 for normal forces and θ = 0.848, β = 0.888 for tangential forces are reported and supposed to be the result of the shrink of the force distribution, which might be caused by the enhancement of very small forces and weakening of very big forces by attractive adhesion forces.