Compaction dynamics of a magnetized powder

Abstract

We have investigated experimentally the influence of a magnetic interaction between the grains on the compaction dynamics of a granular pile submitted to a series of taps. The granular material used to perform this study is a mixture of metallic and glass grains. The packing is immersed in an homogeneous external magnetic field. The magnetic field induces an interaction between the metallic grains that constitutes the tunable cohesion. The compaction characteristic time and the asymptotic packing fraction have been measured as a function of the Bond number which is the ratio between the cohesive magnetic force and the grain weight. These measurements have been performed for different fractions of metallic beads in the pile. When the pile is only made of metallic grains, the characteristic compaction time increases as the square root of the Bond number. While the asymptotic packing fraction decreases as the inverse of the Bond number. For mixtures, when the fraction of magnetized grains in the pile is increased, the characteristic time increases while the asymptotic packing fraction decreases. A simple mesoscopic model based on the formation of granular chains along the magnetic field direction is proposed to explain the observed macroscopic properties of the packings.

Insertion and confinement of hydrophobic metallic powder in water: The bubble-marble effect

“…2. Its critical angle is observed as 2β ∼ 110 • , in agreement with an analysis of self-assembled structures of magnetic powder under magnetic fields [18].…”

Influence of cohesive forces on the macroscopic properties of granular assemblies

“…The granular material used to perform this study is a metallic powder [10]. The average diameter of the metallic grains is d=100 μm with a polydispersity of about 50%.The packing is immersed in an homogeneous vertical magnetic field.…”

“…In this paper, we show that the recent fundamental works concerning the granular compaction dynamics performed in different research groups [9,10,11,13,14,15,16,17] allow to improve this old techniques. In particular, we use the granular compaction measurement to analyze the influence of the cohesive forces on the packing fraction and on the compaction dynamics of a granular pile.…”

“…The friction forces are influenced by the surface properties and by the chemical nature of the grains. The cohesive forces are induced by the presence of liquid bridges [2,3], electric charges [4,5], van der Waals interactions [6] and magnetic dipole-dipole interactions [7,8,9,10,11]. The predominance of one of these cohesive forces depends on both the environmental condition and the physicol-chemical properties of the grains.…”

Micromechanical Analysis of Compaction and Drilling of Granular Media- A Review

“…Examples include: avalanches, segregation (which grains of different type separate under vibration), crystallization (when grains arrange into ordered configurations), pattern formation (when grains arrange into patterns, such as dunes or ripples) or jamming (when the flow of grains stops abruptly) [1]. Micromechanical analysis of compaction and particulate/granular materials has been of significance to academics and industrial communities, from beach sandcastles to chemical, pharmaceutical, food, mechanical, civil, mining and petroleum engineering as well as underground reservoir industry, and materials processing sectors [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Granular media are thermal, quite normal after all, usually with different particle-scale properties and inter-particle interactions, which are responsible for their complex behaviors at the low gravitational environment and macroscopic scale and difficult to assess experimentally [6,11,12,[16][17][18][19][20][21][22].…”