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

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...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-06, Vol.117 (23), p.12611-12617
Main Authors: Varchanis, Stylianos, Haward, Simon J., Hopkins, Cameron C., Syrakos, Alexandros, Shen, Amy Q., Dimakopoulos, Yannis, Tsamopoulos, John
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Deformation
Elongation
Microfluidics
Physical Sciences
Scaling laws
Solid state
Strain
Stress distribution
Velocity distribution
Yield strength
Yield stress
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Summary: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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1922242117