Local Origin of Global Contact Numbers in Frictional Ellipsoid Packings
Date
2015
Authors
Schaller, F.M.
Neudecker, Max
Saadatfar, Mohammad
Delaney, Gary W.
Schröder-Turk, Gerd E.
Schröter, Matthias
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Volume Title
Publisher
American Physical Society
Abstract
In particulate soft matter systems the average number of contacts Z of a particle is an important predictor of the mechanical properties of the system. Using x-ray tomography, we analyze packings of frictional, oblate ellipsoids of various aspect ratios α, prepared at different global volume fractions φg. We find that Z is a monotonically increasing function of φg for all α. We demonstrate that this functional dependence can be explained by a local analysis where each particle is described by its local volume fraction φl computed from a Voronoi tessellation. Z can be expressed as an integral over all values of φl: Z(φg,α,X)=∫Zl(φl,α,X)P(φl|φg)dφl. The local contact number function Zl(φl,α,X) describes the relevant physics in term of locally defined variables only, including possible higher order terms X. The conditional probability P(φl|φg) to find a specific value of φl given a global packing fraction φg is found to be independent of α and X. Our results demonstrate that for frictional particles a local approach is not only a theoretical requirement but also feasible.
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Source
Physical Review Letters
Type
Journal article
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Access Statement
Open Access