Details

Autor(en) / Beteiligte

• Coulais, C
• Behringer, R. P
• Dauchot, O

Titel

How the ideal jamming point illuminates the world of granular media

Ist Teil von

• Soft matter, 2014-01, Vol.1 (1), p.1519-1536

Ort / Verlag

England: Royal Society of Chemistry

Erscheinungsjahr

2014

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The zero temperature properties of frictionless soft spheres near the jamming point have been extensively studied both numerically and theoretically; these studies provide a reliable base for the interpretation of experiments. However, recent work by Ikeda et al. showed that, in a parameter space of the temperature and packing fraction, experiments to date on colloids have been rather far from the theoretical scaling regime. An important question is then whether theoretical results concerning point- J are applicable to any physical/experimental system, including granular media, which we consider here. On the surface, such a-thermal, frictional systems might appear even further from the idealized case of thermal soft spheres. In this work we address this question via experiments on shaken granular materials near jamming. We have systematically investigated such systems over a number of years using hard metallic grains. The important feature of the present work is the use of much softer grains, cut from photoelastic materials, making it possible to determine forces at the grain scale, the details of the contact networks and the motion of individual grains. Using this new type of particle, we first show that the contact network exhibits remarkable dynamics. We find strong heterogeneities, which are maximum at the packing fraction *, distinct from and smaller than the packing fraction † , where the average number of contacts per particle, z , starts to increase. In the limit of zero mechanical excitation, these two packing fractions converge at point J . We also determine dynamics on time scales ranging from a small fraction of the shaking cycle to thousands of cycles. We can then map the observed system behavior onto results from simulations of ideal thermal soft spheres. Our results indicate that the ideal jamming point indeed illuminates the world of granular media. We fully describe the statics and the dynamics of the contact, force, neighbours network of 2D vibrated granular media close to the Jamming transition. We unearth the emerging dynamical and structural criticality and demonstrate that it shares striking similarities with results reported on ideal thermal soft spheres.