Equation of state for random sphere packings with arbitrary adhesion and friction

Condensed Matter journal club

Equation of state for random sphere packings with arbitrary adhesion and friction

  • Event time: 11:30am until 12:30pm
  • Event date: 17th February 2017
  • Speaker: (School of Physics & Astronomy, University of Edinburgh)
  • Location: Room 4312,

Event details

We systematically generate a large set of random micro-particle packings over a wide range of adhesion and friction by means of adhesive contact dynamics simulation. The ensemble of generated packings covers a range of volume fractions ϕ from 0.135 ± 0.007 to 0.639 ± 0.004, and of coordination numbers Z from 2.11 ± 0.03 to 6.40 ± 0.06. We determine ϕ and Z at four limits (random close packing, random loose packing, adhesive close packing, and adhesive loose packing), and find a universal equation of state ϕ(Z) to describe packings with arbitrary adhesion and friction. From a mechanical equilibrium analysis, we determine the critical friction coefficient μf,c: when the friction coefficient μf is below μf,c, particles' rearrangements are dominated by sliding, otherwise they are dominated by rolling. Because of this reason, both ϕ(μf) and Z(μf) change sharply across μf,c. Finally, we generalize the Maxwell counting argument to micro-particle packings, and show that the loosest packing, i.e., adhesive loose packing, satisfies the isostatic condition at Z = 2.

Event resources

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