title: Dynamic shear jamming in dense granular suspensions under extension.
abstract: Unlike dry granular materials, a dense granular suspension like cornstarch in water can strongly resist extensional flows. At low extension rates, such a suspension behaves like a viscous fluid, but rapid extension results in a response where stresses far exceed the predictions of lubrication hydrodynamics and capillarity. To understand this remarkable mechanical response, we experimentally measure the normal force imparted by a large bulk of the suspension on a plate moving vertically upward at a controlled velocity. We observe that, above a velocity threshold, the peak force increases by orders of magnitude. Using fast ultrasound imaging we map out the local velocity profiles inside the suspension, which reveal the formation of a growing jammed region under rapid extension. This region interacts with the rigid boundaries of the container through strong velocity gradients, suggesting a direct connection to the recently proposed shear-jamming mechanism.
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Sayantan
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.|Engineering and the Environment, University of Southampton, Highfield, Southampton S017 1BJ, United Kingdom.
authors.forename: Ivo R
authors.initials: IR
authors.lastname: Peters
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Endao
authors.initials: E
authors.lastname: Han
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Heinrich M
authors.initials: HM
authors.lastname: Jaeger