Microscopic Activated Dynamics Theory of the Shear Rheology and Stress Overshoot in Ultra-Dense Glass-Forming Fluids and Colloidal Suspensions

Abstract

We formulate a microscopic, force-level, activated dynamics-based statistical-mechanical theory for the continuous startup nonlinear shear-rheology of ultra-dense glass-forming hard-sphere fluids and colloidal suspensions in the context of the ECNLE approach. Activated structural relaxation is described as a coupled local-nonlocal event involving caging and longer-range collective elasticity which controls the characteristic stress relaxation time. Theoretical predictions for the deformation-induced mobility enhancement, onset of relaxation acceleration at low values of stress, strain, or shear-rate, apparent power-law thinning of the steady-state structural relaxation time and viscosity, a non-vanishing activation barrier in the shear-thinning regime, an apparent Herschel-Bulkley form of the rate dependence of the steady-state shear stress, exponential growth of different measures of a dynamic yield or flow-stress with packing fraction, and reduced fragility and dynamic heterogeneity under deformation were previously shown to be in good agreement with experiment. The central new question addressed here is the defining feature of the transient response - the stress-overshoot. In contrast to the steady-state flow regime, understanding the transient response requires an explicit treatment of the coupled nonequilibrium evolution of structure, elastic modulus, and stress relaxation time. We formulate a new quantitative model for this aspect in a physically motivated and computationally tractable manner. Theoretical predictions for the stress-overshoot are shown to be in good agreement with experimental observations in the metastable ultra-dense regime of hard-sphere colloidal suspensions as a function of shear-rate and packing fraction, and accounting for deformation-assisted activated motion is crucial for both the transient and steady-state responses.

References in corpus (16)

• Theoretical perspective on the glass transition and amorphous materials
• Three-dimensional imaging of colloidal glasses under steady shear
• Shear banding, aging and noise dynamics in soft glassy materials
• Creep and flow of glasses: strain response linked to the spatial distribution of dynamical heterogeneities
• Overshoots in stress strain curves: Colloid experiments and schematic mode coupling theory
• Microscopic origin of nonlinear non-affine deformation and stress overshoot in bulk metallic glasses
• Start-up Shear of Concentrated Colloidal Hard Spheres: Stresses, Dynamics and Structure
• Tensorial Constitutive Models for Disordered Foams, Dense Emulsions, and other Soft Nonergodic Materials
• Stress Overshoots in Simple Yield Stress Fluids
• Finite-disorder critical point in the yielding transition of elasto-plastic models
• Microscopic Theory of the Influence of Strong Attractive Forces on the Activated Dynamics of Dense Glass and Gel Forming Fluids
• Nonaffine deformation and tunable yielding of colloidal assemblies at the air-water interface
• Continuum modelling of shear start-up in soft glassy materials
• Transient stress evolution in repulsion and attraction dominated glasses
• Rheology finds distinct glass and jamming transitions in emulsions
• Rheology of Hard Glassy Materials

Cited by in corpus (3)

• Ductile-to-brittle transition and yielding in soft amorphous materials: perspectives and open questions
• Microscopic Theory of the Elastic Shear Modulus and Length-Scale-Dependent Dynamic Re-Entrancy Phenomena in Very Dense Sticky Particle Fluids
• Microscopic Basis for Recovery Rheology and the Nonequilibrium Structure,Yielding, and Flow of Dense Particle Suspensions