Abstract

By means of a stress imposed rheometer coupled with a "vibrating cell", generating a Brownian motion at a macroscopic scale into the samples, we have shown that dense-phase vibrated powders exhibit rheological behaviours archetypal of non-Newtonian visco-elastic fluids. These behaviours have been accurately described through a free volume structural model based on simple "stick-slip" granular interactions. As a result, the evolution of the steady state viscosity has been accurately expressed as a function of the shear rate, the frictional stress, the granular pressure, the vibration frequency, the vibration energy, the intergranular contact network mean life and the free volume distribution. The model is consistent with Hookean, Coulombian and Newtonian limits and is not only descriptive but also explicative and predictive of the encountered phenomena. In particular, a "time-granular temperature superposition principle", theoretically predicted by the model, has been experimentally verified, the "granular temperature" being controlled through the vibration energy and frequency. Moreover, this superposition principle has been precisely described by a "Vogel-Fulcher-Tammann" law, leading to very close analogies with molecular systems near their glass transition point.
 

 

Speaker's CV

Philippe MARCHAL

• Docteur de l'Institut National Polytechnique de Lorraine
• Ingénieur du Conservatoire National des Arts et Métiers
Philippe.Marchal@ensic.inpl-nancy.fr GEMICO - ENSIC
Tél. +33 (0)3 83 17 51 43 1, rue Grandville BP20451
Fax +33 (0)3 83 17 53 19 F-54001 Nancy - FRANCE
PhD Thesis : "Eléments de physique statistique appliqués à la rhéologie des milieux granulaires: le modèle du château de sables mouvants", Thèse INPL en Génie des Procédés, Nancy (2002).
Engineer Thesis : "Rhéologie structurale de dispersions argileuses additionnées de polymères". Thèse CNAM en Méthodes Physiques d'Analyses Chimiques, Nancy (1995).
BOOK CHAPTERS
L. Choplin, Ph Marchal, V. Sadtler, D. Della Valle, "Emulsification" in Mise en œuvre des matières agroalimentaires, Hermès-Lavoisier (2006).
Ph Marchal, N. Smirani and L. Choplin, "Rhéologie des milieux granulaires denses vibrés" in Formulation des solides divisés, Cahiers de Formulation - EDP Sciences (2007).
PUBLICATIONS
26 publications - 40 Conference proceedings - 3 application notes.
ORAL PRESENTATIONS (international congress, workshops, symposia):
12 invited conferences - 11 oral communications - 5 posters.
PATENT in collaboration with TA Instruments:
"System and method for rheological characterization of granular materials", Ph. Marchal, L. Choplin, N. Smirani, United States Patent 6 971 262, December 6, 2005.