Eur. Phys. J. E 4, 355-361

Rheology and aging: A simple approach

C. Derec¹, A. Ajdari¹ and F. Lequeux<sup>2

1</sup>  Laboratoire de Physico-Chimie Théorique, Esa CNRS 7083, ESPCI, 10 rue Vauquelin, F-75231 Paris Cedex 05, France
²  Laboratoire de Physico-Chimie Macromoléculaire, UMR CNRS 7615, ESPCI, 10 rue Vauquelin, F-75231 Paris Cedex 05, France

derec@turner.pct.espci.fr

(Received 14 June 2000)

Abstract
We introduce a rheological model to describe the low-frequency mechanical properties of systems near a fluid/paste transition. We propose a Landau-like expansion for the vicinity of this transition, treating the stress relaxation rate as an order parameter. This leads to a formally simple model that allows us to describe the interplay between aging and non-linearities in the mechanical response of the system. We focus here on systems prepared by fluidification under a strong shear, on which mechanical measurments are performed (oscillatory rheology, stress relaxation, response to a steady shear rate), after a waiting time during which the system evolves on its own.

PACS
62.20.Fe - Deformation and plasticity.
83.20.-d - Constitutive relations.
83.50.Gd - Nonlinear viscoelasticity.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001