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 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.

On the kinematics and dynamics of crystal‐rich systems

“…The Sommerfeld number (39) provides the criteria for this transition between boundary and hydrodynamic states of lubrication and explains why there are two states of jamming possible in a hydrogranular systems: (1) In the hydrodynamic lubrication case, jamming occurs closer to a single value of ϕ and is not sensitive to values of particle friction coefficient, and (2) a so-called shear-jamming regime, associated with the onset of frictional contacts, the emergence of a force chain network, and a value of ϕ pc that is not single-valued and depends explicitly on the value of the particle-particle friction coefficient. The emergence of frictional behavior is now understood as contributing to continuous (suspension viscosity is proportional to shear rate) and producing discontinuous (large discontinuous jumps in suspension viscosity as a function of shear rate) shear thickening as well [Clavaud et al, 2017;Lin et al, 2015;Majumdar et al, 2017;Mari et al, 2014;Ness and Sun, 2015, 2016a, 2016bPeters et al, 2016;Royer et al, 2016;Wyart and Cates, 2014].…”

“…A corollary to the rapid onset of frictional behavior as a function of the applied stress is the observation that hydrogranular materials can undergo progressive mechanical "solidification," upon impact [Jerome et al, 2016;Peters et al, 2016;Waitukaitis and Jaeger, 2012], a condition that occurs under extension as well [Majumdar et al, 2017]. Although pore pressure excursions associated with either dilation or compression upon impact (particle volume increase or decrease) mediate the onset of the boundary-lubrication frictional regime [Jerome et al, 2016], the occurrence of a jamming front that propagates away from the point of impact is well documented.…”

Shear fronts in shear-thickening suspensions

“…Efforts to map out a state diagram that delineates the properties of dense suspensions as a function of packing fraction and imposed forcing have focused almost exclusively on steady-state conditions. This does not capture the many remarkable transient phenomena exhibited by suspensions [6,[23][24][25][26][27][28][29][30]. Among these, impact-activated solidification is commonly referred to, but also is one of the least well understood.…”

“…Only a couple years ago was it discovered [25,26] that this solidification is not simply strong shear thickening, as previously assumed, but a dynamic process where impact at the suspension surface initiates jamming fronts that rapidly propagate into the bulk of the material. Recent ultrasound experiments revealed that these fronts constitute localized bands of intense shear that transforms the suspension from a fluid-like into a solid-like state without measurably increasing the particle packing fraction [28,30]. So far, however, * E-mail: endao.han1988@gmail.com several key aspects have remained largely unresolved, including (i) the conditions under which dense suspensions can develop jamming fronts; (ii) the shape of the flow profile at the front; and importantly (iii) the constitutive relation between the applied stress and the front speed.…”

Dynamic jamming of dense suspensions under tilted impact

“…Previous experiments have shown that jamming proceeds via fronts of localized, intense shear, which spread out from the point of forcing, rapidly propagate into the suspension, and change the suspension from a fluid to a solid-like state. Different types of forcing, such as impact, shear, and extension, were observed to generate similar dynamic jamming fronts [10,11,[24][25][26]. However, in all of these cases it was sufficient to perform two-dimensional (2D) imaging of the evolution of the associated flow field, given its axial or radial symmetry.…”