Localized transient jamming in discontinuous shear thickening
Localized transient jamming in discontinuous shear thickening
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DOI：
10.1122/1.5145111
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发表时间：
2020-03-01
影响因子：
3.3
通讯作者：
Urbach, Jeffrey S.
中科院分区：
文献类型：
--
作者：
Rathee, Vikram;Blair, Daniel L.;Urbach, Jeffrey S.
我们报告的直接测量的空间分辨的表面应力在整个表面的致密悬浮液在不连续剪切增稠（DST）使用边界应力显微镜（BSM）在平行板流变仪。我们发现，在DST开始时的大的波动的体积流变响应的结果是本地化的过渡到一个状态，具有非常高的应力，与充分堵塞的固体，使直接接触的剪切边界一致。这种堵塞的类固体相（SLP）迅速断裂，产生两个单独的SLP，沿相反方向传播。通过比较SLP的传播速度与限制板的运动，我们推断出一个保持与底部边界接触，另一个保持与顶部接触。这些区域生长、分叉，并最终以复杂的方式相互作用和衰减，这取决于测量条件（恒定剪切速率与恒定应力）。在恒定施加应力模式下，BSM直接显示了标准体流变学中完全忽略的剧烈应力波动。
We report direct measurements of spatially resolved surface stresses over the entire surface of a dense suspension during discontinuous shear thickening (DST) using boundary stress microscopy (BSM) in a parallel-plate rheometer. We find that large fluctuations in the bulk rheological response at the onset of DST are the result of localized transitions to a state with very high stress, consistent with a fully jammed solid that makes direct contact with the shearing boundaries. This jammed solidlike phase (SLP) is rapidly fractured, producing two separate SLPs that propagate in opposite directions. By comparing the speed of propagation of the SLPs with the motion of the confining plates, we deduce that one remains in contact with the bottom boundary and the other remains in contact with the top. These regions grow, bifurcate, and eventually interact and decay in a complex manner that depends on the measurement conditions (constant shear rate vs constant stress). In a constant applied stress mode, BSM directly reveals dramatic stress fluctuations that are completely missed in the standard bulk rheology.