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Issue 2, 2017
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Equation of state for random sphere packings with arbitrary adhesion and friction

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Abstract

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.

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

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Publication details

The article was received on 29 Sep 2016, accepted on 29 Nov 2016 and first published on 29 Nov 2016


Article type: Paper
DOI: 10.1039/C6SM02216B
Citation: Soft Matter, 2017,13, 421-427
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    Equation of state for random sphere packings with arbitrary adhesion and friction

    W. Liu, Y. Jin, S. Chen, H. A. Makse and S. Li, Soft Matter, 2017, 13, 421
    DOI: 10.1039/C6SM02216B

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