Stretch and flow: Research published in PNAS sheds light on unusual properties of well-known materials

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Experiments confirm numerical predictions for the normal stresses and extensional properties of elasto-viscoplastic materials -  a fruitful collaboration of The Fluids Lab, University of Patras  and the Micro/Bio/ Nanofluidics Unit, Okinawa Institute of Science and Technology, Japan


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

Journal: Proceedings of the National Academy of Sciences of the USA (PNAS), IF=9.58.


The stress-induced transition from solid to liquid state is commonly referred to as “yielding.” Yield-stress materials, including pastes, muds, blood, crude oil, and condiments like mayonnaise, have solid-like properties at rest but can be made to yield and flow under sufficient applied stress. Despite their ubiquity and importance, the existing 100-y-old theory describing the behavior of such materials is only well verified under basic conditions of applied shear stress and assumes that the solid state is undeformable. Experiments and simulations conducted under pure extension provide fundamental information on the behavior of yield-stress materials and demand an overhaul of the current standard theory in order to account for material deformation in the solid-like state prior to yielding and flow.


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