Ikeda Atsushi, Berthier Ludovic
Laboratoire Charles Coulomb, UMR 5221, CNRS and Université Montpellier 2, Montpellier, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Nov;88(5):052305. doi: 10.1103/PhysRevE.88.052305. Epub 2013 Nov 8.
The yield stress is a defining feature of amorphous materials which is difficult to analyze theoretically, because it stems from the strongly nonlinear response of an arrested solid to an applied deformation. Mode-coupling theory predicts the flow curves of materials undergoing a glass transition and thus offers predictions for the yield stress of amorphous solids. We use this approach to analyze several classes of disordered solids, using simple models of hard-sphere glasses, soft glasses, and metallic glasses for which the mode-coupling predictions can be directly compared to the outcome of numerical measurements. The theory correctly describes the emergence of a yield stress of entropic nature in hard-sphere glasses, and its rapid growth as density approaches random close packing at qualitative level. By contrast, the emergence of solid behavior in soft and metallic glasses, which originates from direct particle interactions is not well described by the theory. We show that similar shortcomings arise in the description of the caging dynamics of the glass phase at rest. We discuss the range of applicability of mode-coupling theory to understand the yield stress and nonlinear rheology of amorphous materials.
屈服应力是无定形材料的一个决定性特征，由于它源于受阻固体对施加变形的强烈非线性响应，所以很难从理论上进行分析。模式耦合理论预测了经历玻璃化转变的材料的流动曲线，从而为无定形固体的屈服应力提供了预测。我们使用这种方法来分析几类无序固体，使用硬球玻璃、软玻璃和金属玻璃的简单模型，对于这些模型，模式耦合预测可以直接与数值测量结果进行比较。该理论正确地描述了硬球玻璃中熵性质屈服应力的出现，以及在定性水平上随着密度接近随机密堆积时其快速增长。相比之下，源于直接粒子相互作用的软玻璃和金属玻璃中固体行为的出现，该理论并未很好地描述。我们表明，在静止玻璃相的笼蔽动力学描述中也会出现类似的缺点。我们讨论了模式耦合理论在理解无定形材料的屈服应力和非线性流变学方面的适用范围。
