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arXiv · 1511.02219

Self-organized magnetic particles to tune the mechanical behaviour of a granular system

Meredith Cox·Dong Wang·Jonathan Barés·Robert P. Behringer
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Abstract

Above a certain density a granular material jams. This property can be controlled by either tuning a global property, such as the packing fraction or by applying shear strain, or at the micro-scale by tuning grain shape, inter-particle friction or externally controlled organization. Here, we introduce a novel way to change a local granular property by adding a weak anisotropic magnetic interaction between particles. We measure the evolution of the pressure, $P$, and coordination number, $Z$, for a packing of 2D photo-elastic disks, subject to uniaxial compression. Some of the particles have embedded cuboidal magnets. The strength of the magnetic interactions between particles are too weak to have a strong direct effect on $P$ or $Z$ when the system is jammed. However, the magnetic interactions play an important role in the evolution of latent force networks when systems containing a large enough fraction of the particles with magnets are driven through unjammed states. In this case, a statistically stable network of magnetic chains self-organizes and overlaps with force chains, strengthening the granular medium. We believe this property can be used to reversibly control mechanical properties of granular materials.

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Meredith Cox, Dong Wang, Jonathan Barés, Robert P. Behringer. 2015-11-06. Self-organized magnetic particles to tune the mechanical behaviour of a granular system. https://doi.org/10.1209/0295-5075%2F115%2F64003

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