A unified approach to model elasto-viscoplastic thixotropic yield-stress materials and apparent yield-stress fluids
A unified approach to model elasto-viscoplastic thixotropic yield-stress materials and apparent yield-stress fluids
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DOI：
10.1007/s00397-013-0699-1
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发表时间：
2013-07-01
期刊：
影响因子：
2.3
通讯作者：
Thompson, Roney L.
中科院分区：
文献类型：
--
作者：
de Souza Mendes, Paulo R.;Thompson, Roney L.
提出了一种弹粘塑性触变材料的本构模型。它由两个微分方程组成，一个是应力方程，另一个是结构参数方程，结构参数是表示微结构结构化程度的标量。与以前的这种模型相比，结构参数从零变化到一个正数，通常是一个很大的数字。下限对应于完全非结构化的材料，而上限对应于完全结构化的材料。当上限是有限的，该模型代表了一个高度剪切稀化，触变性，粘弹性液体，具有明显的屈服应力。当它趋于无穷大时，就达到了真实屈服应力材料的行为。流变流量，如恒定剪切速率试验，蠕变试验，SAOS，和大振幅振荡剪切（LAOS）的预测，它表明，在所有情况下，实验观察到的趋势忠实地再现模型。在此模型框架内，对雪崩效应和剪切带现象给出了简单的解释。LAOS的结果是特别重要的，因为它们提供了一条信息，迄今为止是在文献中，即Lissajous-Bowditch曲线形状和流变效应，如弹性，触变性和屈服之间的定量联系。
A constitutive model for elasto-viscoplastic thixotropic materials is proposed. It consists of two differential equations, one for the stress and the other for the structure parameter, a scalar quantity that indicates the structuring level of the microstructure. In contrast to previous models of this kind, the structure parameter varies from zero to a positive and typically large number. The lower limit corresponds to a fully unstructured material, whereas the upper limit corresponds to a fully structured material. When the upper limit is finite, the model represents a highly shear-thinning, thixotropic, and viscoelastic liquid that possesses an apparent yield stress. When it tends to infinity, the behavior of a true yield-stress material is achieved. Predictions for rheometric flows such as constant shear rate tests, creep tests, SAOS, and large-amplitude oscillatory shear (LAOS) are presented, and it is shown that, in all cases, the trends observed experimentally are faithfully reproduced by the model. Within the framework of the model, simple explanations are given for the avalanche effect and the shear banding phenomenon. The LAOS results obtained are of particular importance because they provide a piece of information that so far is absent in the literature, namely a quantitative link between the Lissajous-Bowditch curve shapes and rheological effects such as elasticity, thixotropy, and yielding.