Transition between solid and liquid state of yield-stress fluids under purely extensional deformations

Abstract

We report experimental microfluidic measurements and theoretical modeling of elastoviscoplastic materials under steady, planar elongation. Employing a theory that allows the solid state to deform, we predict the yielding and flow dynamics of such complex materials in pure extensional flows. We find a significant deviation of the ratio of the elongational to the shear yield stress from the standard value predicted by ideal viscoplastic theory, which is attributed to the normal stresses that develop in the solid state prior to yielding. Our results show that the yield strain of the material governs the transition dynamics from the solid state to the liquid state. Finally, given the difficulties of quantifying the stress field in such materials under elongational flow conditions, we identify a simple scaling law that enables the determination of the elongational yield stress from experimentally measured velocity fields.

Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Description of the Model and Rheological Predictions

“…Nevertheless, since blood is a suspension of elastic particles (RBCs) in a viscoelastic solvent (plasma), we can make some theoretical considerations regarding the quantitative predictions of our model in uniaxial elongation. The small plateau that arises in the plastic regime is in accordance with recent experimental measurements of "the normal yield stress in elongation" in various jammed systems [98] and is expected to be present in extensional experiments with blood. The subsequent regime, where N 1 rises smoothly, corresponds to the onset of viscous fw and thixotropic phenomena related to the destruction of the rouleaux.…”

Acoustic Bubble Dynamics in a Yield-Stress Fluids

“…First, the size of the yielded region around the bubble remains small for all our experiments -for which ζ ≤ 0.08-and rising motion is therefore very confined [20]. It could also be related to a failure of the von Mises yield criterion [Equation (10)] for bulk yielding in extension, as already reported in other simple yield-stress fluids [51][52][53]. Another possibility lies in finite-size effects given the relatively small size of the bubble compared to the constitutive elements of Carbopol.…”

Progress in rheology and hydrodynamics allowed by NMR or MRI techniques

“…pastes or concentrated suspensions) this must rely on an appropriate program and the implementation of a relevant tensorial constitutive equation, the latter point being still a matter of intense debate in the field of yield stress fluids (Saramito 2007, Saramito and Wachs 2017, Mendes 2011, Mendes and Thompson 2012, Fraggedakis et al 2016, Bleyer et al 2015, Chaparian and Frigaard 2017, Dimitriou and McKinley 2019. Finally, except in some cases a, Varchanis et al 2020 the validity of these constitutive equations is essentially tested from the analysis of simple shear flows. For simple expressions this can be straightforward: this is for example the case of the basic 3D Herschel-Bulkley expression (Coussot 2005) which contains no more parameters than in the simple shear expression; however, as for the others, this tensorial expression has not been proved to apply for more complex flows.…”