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Thursday, March 29, 2018 at 2:00pm to 3:00pm
Physical Sciences Building, 416
245 East Avenue
CANCELLED
Shear jamming fronts in dense suspensions
Suspensions are mixtures of solid particles and a liquid. While perturbed gentlly, they behave as a viscous fluid. However, when they are submitted to a sudden driving force at a boundary (e.g. under impact), a front can be generated, which propagates into the bulk and turns the suspension into a solid-like material in its wake. To explain this phenomenon, we used high-speed ultrasound to directly image flows inside these optically opaque materials. We showed that the suspensions are jammed due to shear instead of increase in the local particle volume fraction as people expected before. We further showed that shear thickening and shear jamming can be understood under a unified framework, not only in steady-state systems, but also in transient phenomena. We found the missing piece that connects steady-state rheology and transient shear flows, which is a characteristic strain scale. Based on this idea, we generalized a phenomenological model by Wyart and Cates for steady-state rheology [1] by introducing a strain term. With the generalized model, we derived a constitutive relation for suspensions in the dynamic jamming regime. The predictions of the model were tested experimentally with a quasi-one dimensional system, and the results match well.
Hosted by Itai Cohen