Mechanics of amorphous and polymeric matter

本研究计划采用理论和计算机模拟来探索结构无序和远离平衡的聚合物的力学行为。无序材料的实例包括无定形金属、许多软玻璃如泡沫、糊剂、乳液和致密胶体悬浮液或电池组件。在这些材料中，变形机制比结晶固体更不容易理解，在结晶固体中，作为塑性流动载体的缺陷的运动很容易识别。现有的工程描述往往侧重于平均行为，当波动变得很大时就会失败。在这里，我们寻求一个基本的理解的微观起源的非晶金属和屈服应力流体的流变行为，以便能够调整和改善其机械性能。控制应力和应变率的流变流动规则不仅具有强非线性，而且在材料屈服时具有空间非局部协同性。这种协同性导致变形局部化为剪切带，这目前阻碍了金属玻璃的广泛应用。在这里，我们将连接分子模拟的颗粒尺度上的介观和连续尺度上的粗描述定量构建一个预测的统计理论的非晶物质的塑性流动。

This research program employs theory and computer simulations to explore the mechanical behavior of structurally disordered and polymeric matter far from equilibrium. Examples of disordered materials include amorphous metals, many soft glasses such as foams, pastes, emulsions, and dense colloidal suspensions or cell assemblies. In these materials, deformation mechanisms are much less understood than in crystalline solids, where the motion of defects as carriers of plastic flow is easily identified. Existing engineering descriptions tend to focus on average behavior and fail when fluctuations become large. Here we seek a fundamental understanding of the microscopic origin of the rheological behaviour of amorphous metals and yield stress fluids in order to be able to tune and improve their mechanical properties. The rheological flow rules governing stress and strain rate are not only strongly nonlinear, but also imply spatial nonlocal cooperativity when the material yields. This cooperativity leads to the localization of deformation into shear bands, which currently precludes widespread applications of metallic glasses. Here, we will connect molecular simulations on the particle scale quantitatively with coarser descriptions on mesoscopic and continuum scales to construct a predictive statistical theory of plastic flow of amorphous matter.