论文标题
振荡剪切过程中不连续剪切增厚悬浮液中边界应力的动力和记忆
Dynamics and memory of boundary stresses in discontinuous shear thickening suspensions during oscillatory shear
论文作者
论文摘要
我们报告使用边界应力显微镜在不连续的剪切增厚方案中的大幅度振荡剪切（LAOS）中直接测量了在大振幅振荡剪切（LAOS）期间的空间分辨的表面应力。与以前的研究一致，大量流变学表明，高于频率依赖性临界应力的复杂粘度急剧增加。我们发现，粘度的增加与较大的异质边界应力的出现是一致的，这表明与粒径相比，空间尺度上的瞬时固体样相（SLP）形成。 SLP的出现的临界应力在很大程度上取决于峰值振荡应力，这取决于峰剪切速率和频率依赖性悬浮液粘度。 SLP在每个周期上消散和改革，其空间模式在低频下具有高度可变，但在最高频率（$ω= 10 $ rad/sec）下非常持久。
We report direct measurements of spatially resolved surface stresses of a dense suspension during large amplitude oscillatory shear (LAOS) in the discontinuous shear thickening regime using boundary stress microscopy. Consistent with previous studies, bulk rheology shows a dramatic increase in the complex viscosity above a frequency-dependent critical strain. We find that the viscosity increase is coincident with that appearance of large heterogeneous boundary stresses, indicative of the formation of transient solid-like phases (SLPs) on spatial scales large compared to the particle size. The critical strain for the appearance of SLPs is largely determined by the peak oscillatory stress, which depends on the peak shear rate and the frequency-dependent suspension viscosity. The SLPs dissipate and reform on each cycle, with a spatial pattern that is highly variable at low frequencies but remarkably persistent at the highest frequency measured ($ω= 10$ rad/sec).
