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

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.

5 pages, 4 figures

References in corpus (2)

• The Jamming Transition in Granular Systems
• Packings of 3D stars: Stability and structure

Cited by in corpus (7)

• Photoelastic force measurements in granular materials
• Enlightening force chains: a review of photoelasticimetry in granular matter
• On the Apparent Yield Stress in Non-Brownian Magnetorheological Fluids
• Micromechanical description of the compaction of soft pentagon assemblies
• Jamming transition in non-spherical particle systems: pentagons vs. disks
• `Sinking' in a bed of grains activated by shearing
• Experimental validation of a micromechanically-based compaction law for soft/hard grain mixtures