Séminaires MSC
"Matière et Systèmes Complexes"

Lundi 14 juin 2010 à 11h30
Bâtiment Condorcet, 4ème étage, salle 454 A.

Itai Einav
(School of Civil Engineering, The University of Sydney, currently visiting professor at Université Joseph Fourier, Grenoble)

Grainsize reduction: from discrete to continuum
Comminution, the process of grainsize reduction, is pivotal to many operations and various industries (e.g., mineral processing, agriculture, pharmaceutics). For example, in pharmaceutics, controlled comminution is required for optimising the properties of tablets, including the chemical absorption and the overall strength of tablets. Comminution is also fundamental in geotechnical engineering and geosciences. For example, grain crushing along earthquake faults known to produce the cataclastic gouge. In the process the grainsize distribution evolves towards an ultimate grading, which is often (and conveniently) assumed fractal. The explicit connection between this tendency and the stress-strain constitutive behaviour is not well understood, and requires an effective continuum approach. 
In my talk I will present a new constitutive theory called “breakage mechanics”. The theory is based on principles of continuum mechanics and can explain soil mechanics from a radically new angle, but its predictions are supported by experimental and discrete numerical observations. Two numerical models with deliberately contrasted levels of complexity will confirm universal results that experiments reveal and the theory adopt as an essential ingredient. Examples will be presented to how the theory can be utilised for pharmaceutical tabletting (dominantly compaction), understanding cataclasis (dominantly shear), and petroleum sand production (combined shear-compaction).