Dresden 2011 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 20: Glasses I (jointly with DF and CPP)

DY 20.4: Talk

Wednesday, March 16, 2011, 11:00–11:15, KÖN Farb

Describing experimentally obtained stress overshoots in sheared colloidal dispersions with schematic MCT — •Christian Peter Amann¹, Matthias Fuchs¹, Miriam Siebenbürger², and Matthias Ballauff² — ¹Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany — ²Helmholtz Zentrum für Materialien und Energie, 14109 Berlin, Germany

Sheared viscoelastic media show a stress overshoot between elastic and plastic deformation regime, i.e. a maximum in the shear stress vs. strain plot after switching on a constant shear rate. We found a way to model such overshoots with the F₁₂^(γ̇) model, a schematic model of a microscopic mode-coupling theory (MCT) approach to describe glass forming liquids. The enhancement of the schematic model is tested by fitting experimental strain-stress curves from sheared colloidal dispersions of thermosensitive core-shell particles. Flow curves and linear stress response moduli of the same experimental setup could be fitted well with the F₁₂^(γ̇) model [1]. Furthermore this model has been able to describe nonlinear stress response to oscillatory shear rates [2]. The implementation of stress overshoots in this schematic model was motivated and guided by the recently identified mechanism within microscopic MCT framework causing such overshoots to occur [3]. This mechanism is also identified to be highly connected to a super-diffusive motion regime of the colloids [3].

[1] M. Siebenbürger et al., J. Rheol. 53, 707–726 (2009)

[2] J.M. Brader et al., arXiv:1010.2587v1 (2010)

[3] J. Zausch et al., J. Phys.: Condens. Matter 20, 404210 (2008)