title: Rheological hysteresis in soft glassy materials.
abstract: The nonlinear rheology of a soft glassy material is captured by its constitutive relation, shear stress versus shear rate, which is most generally obtained by sweeping up or down the shear rate over a finite temporal window. For a huge amount of complex fluids, the up and down sweeps do not superimpose and define a rheological hysteresis loop. By means of extensive rheometry coupled to time-resolved velocimetry, we unravel the local scenario involved in rheological hysteresis for various types of well-studied soft materials. We introduce two observables that quantify the hysteresis in macroscopic rheology and local velocimetry, respectively, as a function of the sweep rate δt(-1). Strikingly, both observables present a robust maximum with δt, which defines a single material-dependent time scale that grows continuously from vanishingly small values in simple yield stress fluids to large values for strongly time-dependent materials. In line with recent theoretical arguments, these experimental results hint at a universal time scale-based framework for soft glassy materials, where inhomogeneous flows characterized by shear bands and/or pluglike flow play a central role.
authors: Laboratoire de Physique, École Normale Supérieure de Lyon, Université de Lyon, CNRS UMR 5672, 46 Allée d'Italie, 69364 Lyon cedex 07, France.
authors: Thibaut
authors: T
authors: Divoux
authors: Vincent
authors: V
authors: Grenard
authors: Sébastien
authors: S
authors: Manneville