Force Propagation and Friction in Granular Materials

这是一个结合实验和理论/建模的凝聚态物理项目。目的是了解颗粒材料中的力传播。颗粒材料一直是一个密集和不断增长的研究机构的焦点，也扩展到更广泛的材料类别，如玻璃，胶体，泡沫和其他表现出堵塞（冻结结构）。人们正在发明处理这些材料的新技术，这些材料无法用传统的统计力学来描述。因此，从这个项目中产生的概念有可能影响广泛的材料处理问题，这些问题出现在粮食、煤炭和矿石、医药粉末和其他颗粒材料中。在这些材料中，力由所谓的应力链的不均匀网络承载，这些网络形成和改变，导致强烈的时空应力波动。该项目将解决至少四个不同的系统，表现出力的传播和波动。本工作的理论/建模方面侧重于应力传播的微观/介观模型，而分子动力学技术则用于承受力波动。该项目涉及本科生、研究生和博士后的综合培训和发展计划。更多的高年级学生和博士后通过适当的研究项目来培养本科生。研究生和博士后接受先进研究技术的培训，为他们的学术或工业生涯做好准备。该项目将侧重于颗粒材料的行为，其中包括广泛的技术和工业相关产品，从粮食到煤和矿石到医药粉末。据估计，处理这些材料为美国经济增加的价值每年高达一万亿美元。然而，我们对这些材料的基本物理学的理解是不完整的，这意味着在处理这些材料时相应的生产力损失。这个项目的重点是基本的物理问题，比如这些材料中的力是如何携带的，以及当这些材料受到外力时，比如在处理设备时可能遇到的那些力时，它们是如何表现的。该项目所寻求的重要见解应该包括更好的材料特性的可预测性，以及对这种可预测性的局限性的洞察。该项目涉及本科生、研究生和博士后的综合培训和发展计划。研究生和博士后将通过适当的研究项目帮助本科生。本科生学习关键的研究技术，以及仪器开发方面的培训。研究生和博士后接受先进研究技术的培训，为他们的学术或工业生涯做好准备。

This is a combined experiment and theory/modeling condensed matter physics project. The objective is to understand force propagation in granular materials. Granular materials have been the focus of an intensive and growing body of research that also extends to a broader class of materials, such as glasses, colloids, foams and others that exhibit jamming (frozen structures). New techniques are being invented to deal with these materials, which cannot be described in the context of conventional statistical mechanics. Thus, concepts arising from this project have potential to impact a broad range of materials handling problems, which arise with food grains, coal and ores and pharmaceutical powders and other granular materials. In these materials, forces are carried by an inhomogeneous network of so-called stress chains, which form and reform, leading to strong spatio-temporal stress fluctuations. This project will address at least four different systems that exhibit force propagation and fluctuations. Theory/modeling aspects of this work focus on micro/mesoscopic models of stress propagation, while Molecular Dynamics techniques are brought to bear on force fluctuations. This project involves undergraduates, graduate students and post-docs in an integrated program of training and development. More senior students and post-docs train undergrads through appropriate research projects. Graduate students and post-docs receive training in advanced research techniques that prepare them for either academic or industrial careers.This project will focus on the behavior of granular materials, which include a broad spectrum of technologically and industrially relevant products ranging from food grains to coal and ores to pharmaceutical powders. The value added to the US economy in the handling of these materials is estimated to be as much as a trillion dollars a year. However, our understanding of the basic physics of these materials is incomplete, and this translates into a corresponding loss of productivity in dealing with these materials. This project focuses on such basic physics issues as how forces are carried in these materials and how the materials behave when they are subject to applied forces, such as those that might be encountered in handling devices. Important insights sought with this project should include better predictability of materials properties, as well as insight into the limits of this predictability. This project involves undergraduates, graduate students and post-docs in an integrated program of training and development. Grad students and post-docs will help undergrads through appropriate research projects. Undergraduates learn key research techniques, and also training in instrumentation development. Graduate students and post-docs receive training in advanced research techniques that will prepare them for either academic or industrial careers.