Time-dependent shear rate inhomogeneities and shear bands in a thixotropic yield-stress fluid under transient shear.
Time-dependent shear rate inhomogeneities and shear bands in a thixotropic yield-stress fluid under transient shear.
复制标题
瞬态剪切下触变屈服应力流体中随时间变化的剪切速率不均匀性和剪切带。
作者：
Yufei Wei;M. Solomon;R. Larson
本文研究了触变性气相二氧化硅悬浮液在剪切启动和流动逆转试验中的流变响应、剪切速率不均匀性和剪切带行为。我们发现，这种瞬态剪切下的悬浮液不仅表现出粘弹性，屈服，运动硬化，触变性，但也随时间变化的剪切不均匀性，包括带时，表观剪切速率低于0.1和0.25 s-1之间的临界值。通过多次剪切启动试验和流动逆转试验，发现触变性促进流动非均匀性，而运动硬化抑制流动非均匀性，提出了一个简单的触塑性本构方程，可以定性地预测剪切启动试验和流动逆转试验中流变响应和条带动力学的重要特征。
We study the rheological responses and shear-rate inhomogeneities and shear banding behaviors of a thixotropic fumed silica suspension in shear startup tests and flow reversal tests. We find that this suspension under transient shear exhibits not only viscoelasticity, yielding, kinematic hardening, and thixotropy, but also time-dependent shear inhomogeneities including bands when the apparent shear rate is below a critical value between 0.1 and 0.25 s-1. Through multiple shear startup tests and flow reversal tests, we find that thixotropy promotes flow heterogeneity while kinematic hardening suppresses it. We propose a simple thixo-plastic constitutive equation that can qualitatively predict the important features of the rheological response and banding dynamics in shear startup tests and flow reversal tests.