On regular and random two-dimensional packing of crosses

Stannarius, Ralf; Schulze, Jonas

doi:10.1007/s10035-021-01190-7

Cited by 9 publications

(3 citation statements)

References 51 publications

(82 reference statements)

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“…In experiments, for example, the technology of 3D printing has allowed one to precisely control the shape of particles to be later assembled in structures [31]. Although some studies have performed qualitative characterization of the resistance of non-convex particle assemblies [5,9,10,32], only a few have quantitatively assessed their mechanical response and packing properties [11,[33][34][35][36]. The current technological capabilities suggest that hundreds -or even thousands -of particles can be built and tested in standard devices (triaxial, shear cells, rheometers, etc.).…”

Section: Physical Experimentsmentioning

confidence: 99%

Bespoke particle shapes in granular matter

2022

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Among granular matter, one type of particle has special properties. Upon being assembled in disordered configurations, these particles interlock, hook, almost braid, and – surprisingly, considering their relatively low packing fractions – show exceptional shear strength.Such is the case of non-convex particles. They have been used in the shapes of tetrapods, ‘L’, ‘Z’, stars, and many others, to protect coasts or build self-standing structures requiring no binders or external supports. Although these structures are often designed without a comprehensive mechanical characterization, they have already demonstrated great potential as highly resistant construction materials. Nevertheless, it is natural to attempt to find the most appropriate non-convex shapes for any given application. Can a particle shape be tuned to obtain a desired mechanical behavior? Although this question cannot be answered yet, current technological, simulation, and experimental developments strongly suggest that it can be resolved in the next decade. A clear understanding of the relationships between particle shapes, mechanical response, and packing properties will be key to providing insights into the behavior of these materials. Such work should stand on 1) robust and general shape descriptors that encode the complexity of non-convex shapes (i.e., the number of arms, the symmetries, and asymmetries of the bodies, the presence of holes, etc.), 2) the analysis of the response of assemblies under different loading conditions, and 3) the disposition and reliability of non-convex shapes to ensure durability. The manufacturing process and an efficient use of resources are additional elements that could further help to optimize particle shape. In the quest of designing bespoke non-convex particles, this paper consolidates the challenges that remain unresolved. It also outlines some routes to explore based on the latest developments in technology and research.

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Section: Physical Experimentsmentioning

confidence: 99%

Bespoke particle shapes in granular matter

2022

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“…[9][10][11][12] Nonconvex particles composed of several arms, for example, can be assembled into vertical walls. [12][13][14] Such a configuration corresponds to an angle of repose of 901, a geometry that can be obtained with rounded particles only if cohesive bonds are added between particles. For this reason, shape-induced enhanced strength has been coined 'geometrical cohesion'.…”

Section: Introductionmentioning

confidence: 99%

Contact networks and force transmission in aggregates of hexapod-shaped particles

Tran,

Nezamabadi,

Bayle

et al. 2024

Soft Matter

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“…Some recent studies dealt with crosses: Huet [29] performed simulations and experiments of the collapse of heaps of 2D crosses. Their packing in 2D was investigated theoretically [30][31][32] and experimentally [33,34]. Spatial crosses, also referred to as hexapods, recently received attention.…”

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confidence: 99%

Reversed granular Weissenberg effect in ensembles of sheared non-convex granular particles

Mohammadi¹,

Puzyrev²,

Trittel³

et al. 2022

Preprint

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Studies of granular materials, both theoretical and experimental, are often restricted to convex grain shapes. We demonstrate that a non-convex grain shape can lead to a qualitatively novel macroscopic dynamics. Spatial crosses (hexapods) are continuously sheared in a split-bottom container. Thereby, they develop a secondary flow profile that is completely opposite to that of rod-shaped or lentil-shaped convex grains in the same geometry. The crosses at the surface migrate towards the rotation center and sink there, mimicking an 'inverse Weissenberg effect'. The observed surface flow field suggests the existence of a radial outward flow in the depth of the granular bed, thus forming a convection cell. This flow field is connected with a dimple formed in the rotation center. The effect is strongly dependent on the particle geometry and the height of the granular bed.

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On regular and random two-dimensional packing of crosses

Cited by 9 publications

References 51 publications

Bespoke particle shapes in granular matter

Bespoke particle shapes in granular matter

Contact networks and force transmission in aggregates of hexapod-shaped particles

Reversed granular Weissenberg effect in ensembles of sheared non-convex granular particles

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