Ovarlez Guillaume, Chateau Xavier
Université Paris Est-Institut Navier, Laboratoire des Matériaux et Structures du Génie Civil, 2, Allée Kepler, 77420 Champs-sur-Marne, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061403. doi: 10.1103/PhysRevE.77.061403. Epub 2008 Jun 10.
We study the solid mechanical properties of several thixotropic suspensions as a function of the shear stress history applied during their flow stoppage and their aging in their solid state. We show that their elastic modulus and yield stress depend strongly on the shear stress applied during their solid-liquid transition (i.e., during flow stoppage) while applying the same stress only before or only after this transition may induce only second-order effects: there is negligible dependence of the mechanical properties on the preshear history and on the shear stress applied at rest. We also found that the suspensions age with a structuration rate that hardly depends on the stress history. We propose a physical sketch based on the freezing of a microstructure whose anisotropy depends on the stress applied during the liquid-solid transition to explain why the mechanical properties depend strongly on this stress. This sketch points out the role of the internal forces in the colloidal suspensions' behavior. We finally discuss briefly the macroscopic consequences of this phenomenon and show the importance of using a controlled-stress rheometer.
我们研究了几种触变悬浮液的固体力学性能，这些性能是其流动停止过程中所施加的剪切应力历史以及其在固态下老化的函数。我们表明，它们的弹性模量和屈服应力强烈依赖于固液转变（即流动停止期间）所施加的剪切应力，而仅在此转变之前或之后施加相同应力可能只会产生二阶效应：力学性能对预剪切历史和静止时所施加的剪切应力的依赖性可忽略不计。我们还发现，悬浮液以几乎不依赖于应力历史的结构化速率老化。我们基于微观结构的冻结提出了一个物理模型，该微观结构的各向异性取决于液固转变期间所施加的应力，以解释为何力学性能强烈依赖于该应力。该模型指出了内力在胶体悬浮液行为中的作用。我们最后简要讨论了这一现象的宏观后果，并展示了使用控制应力流变仪的重要性。
