Direct observation of dynamic shear jamming in dense suspensions

Dynamic jamming point for shear thickening suspensions.

We report on rheometry measurements to characterize the critical behavior in two model shear thickening suspensions: cornstarch in water and glass spheres in oil. The slope of the shear thickening part of the viscosity curve is found to increase dramatically with packing fraction and diverge at a critical packing fraction phi(c). The magnitude of the viscosity and the yield stress are also foun...

High-speed ultrasound imaging in dense suspensions reveals impact-activated solidification due to dynamic shear jamming

A remarkable property of dense suspensions is that they can transform from liquid-like at rest to solid-like under sudden impact. Previous work showed that this impact-induced solidification involves rapidly moving jamming fronts; however, details of this process have remained unresolved. Here we use high-speed ultrasound imaging to probe non-invasively how the interior of a dense suspension re...

Dense Suspensions: Force Response and Jamming Stefan von Kann Dense suspensions: Force response and jamming

Generality of shear thickening in dense suspensions.

Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate, that is, they shear thin. Few are reported to do the opposite, that is, shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behaviour. Here we resolve this apparent contradiction. We demonstrate...

Dense colloidal suspensions under time-dependent shear.

We consider the nonlinear rheology of dense colloidal suspensions under a time-dependent simple shear flow. Starting from the Smoluchowski equation for interacting Brownian particles advected by shearing (ignoring fluctuations in fluid velocity), we develop a formalism which enables the calculation of time-dependent, far-from-equilibrium averages. Taking shear stress as an example, we derive ex...