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Non-trivial rheological exponents in sheared yield stress fluids

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Abstract

In this work we discuss possible physical origins of non-trivial exponents in the athermal rheology of soft materials at low but finite driving rates. A key ingredient in our scenario is the presence of a self-consistent mechanical noise that stems from the spatial superposition of long-range elastic responses to localized plastically deforming regions. We study analytically a mean-field model, in which this mechanical noise is accounted for by a stress diffusion term coupled to the plastic activity. Within this description we show how a dependence of the shear modulus and/or the local relaxation time on the shear rate introduces corrections to the usual mean-field prediction, concerning the Herschel–Bulkley-type rheological response of exponent 1/2. This feature of the mean-field picture is then shown to be robust with respect to structural disorder and partial relaxation of the local stress. We test this prediction numerically on a mesoscopic lattice model that implements explicitly the long-range elastic response to localized shear transformations, and we conclude on how our scenario might be tested in rheological experiments.

Graphical abstract: Non-trivial rheological exponents in sheared yield stress fluids

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Publication details

The article was received on 02 Dec 2016, accepted on 25 May 2017 and first published on 30 May 2017


Article type: Paper
DOI: 10.1039/C6SM02702D
Citation: Soft Matter, 2017, Advance Article
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    Non-trivial rheological exponents in sheared yield stress fluids

    E. Agoritsas and K. Martens, Soft Matter, 2017, Advance Article , DOI: 10.1039/C6SM02702D

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