Volume 115, Number 6, September 2016
|Number of page(s)||5|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||04 November 2016|
Self-organized magnetic particles to tune the mechanical behavior of a granular system
1 Department of Physics & Center for Nonlinear and Complex Systems, Duke University - Durham, NC, 27708, USA
2 Laboratoire de Mécanique et de Génie Civil, UMR 5508, Université de Montpellier-CNRS - Montpellier, France
Received: 29 August 2016
Accepted: 14 October 2016
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. A fraction Rm of the particles have embedded cuboidal magnets. The strength of the magnetic interactions between particles is 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 to jammed states. In this case, a statistically stable network of magnetic chains self-organizes before jamming and overlaps with force chains once jamming occurs, strengthening the granular medium. This property opens a novel way to control mechanical properties of granular materials.
PACS: 47.57.Gc – Granular flow / 81.05.Rm – Porous materials; granular materials / 78.20.Fm – Birefringence
© EPLA, 2016
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