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Transient dynamics in dense colloidal suspensions under shear: shear rate dependence.
M Laurati1, K J Mutch, N Koumakis
1Condensed Matter Physics Laboratory, IPkM, Heinrich-Heine University, 40225 Düsseldorf, Germany. marco.laurati@uni-duesseldorf.de
Summary
Investigating supercooled and glassy systems under shear reveals that higher shear rates intensify stress overshoots and super-diffusion. At high shear rates, systems yield more abruptly due to suppressed Brownian motion.
Area of Science:
- Materials Science
- Soft Matter Physics
- Computational Physics
Background:
- Supercooled and glassy systems exhibit complex dynamics under shear.
- Understanding their transient behavior and stress-strain relations is crucial for material design.
Purpose of the Study:
- To investigate the effect of shear rate on transient dynamics and stress-strain relations in supercooled and glassy systems.
- To explore the interplay between microscopic dynamics and macroscopic rheology under shear.
Main Methods:
- Confocal microscopy
- Rheology experiments
- Brownian dynamics (BD) simulations
- Molecular dynamics (MD) simulations
- Mode coupling theory (MCT)
Main Results:
- Increased shear rate enhances super-diffusion in microscopic dynamics and stress overshoot in macroscopic rheology.
- Mode coupling theory (MCT) correlates these phenomena with negative generalized shear modulus sections that grow with shear rate.
- At high shear rates (inverse shear rate much smaller than relaxation time), Brownian motion becomes less significant, leading to earlier and more abrupt yielding.
Conclusions:
- Shear rate significantly alters the yielding transition in supercooled and glassy systems.
- The transition from localization to flow becomes more abrupt at higher shear rates.
- Suppressed Brownian motion at high shear rates leads to increased stress accumulation before yielding.
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