Collaborative research: Studies of aging and memory in granular materials

摘要-0456703-0457431耶鲁大学合作研究：颗粒材料中衰老和记忆的研究W。Losert(马里兰大学物理系、IPST和IREAP)，C.S.O.Hern(耶鲁大学机械工程和物理系)我们寻求对堵塞颗粒材料中的老化和记忆有更深入的了解。我们的研究重点是阻塞状态的结构、缓慢演化和初始失效。我们将使用新的单个颗粒的3D成像技术和互补分子动力学(MD)模拟来研究颗粒材料在剪应力下颗粒尺度特性的缓慢演化。我们相信，这些研究的结果可以用来建立更好的模型来研究受阻颗粒系统中的屈服和流动的启动。智力上的优点：很少有研究能够分析颗粒材料中老化过程中单个颗粒的排列。这在很大程度上是因为在3D中定位颗粒位置的非侵入性和非破坏性技术直到现在才可用。我们将使用几种最先进的技术来研究老化过程中的微观结构：马里兰大学的共焦显微镜和荧光共振能量转移(FRET)，以及法国格勒诺布尔欧洲同步辐射设施的同步加速器X射线显微断层扫描。沃尔夫冈·洛塞特(WL)教授将与教授合作进行实验。雷诺·德兰奈(雷恩)和道格·英格利希(马里兰州)。Corey O.Hern(CO)教授将对摩擦颗粒材料的简单模型进行MD模拟，以指导未来的实验，研究实验获得的阻塞构型的稳定性，并探索实验不易获得的参数区域。CO在无热系统的模拟方面有丰富的经验，并且可以获得充足的计算资源。拟议中的模拟和实验之间的合作将使我们在开发颗粒材料中老化和历史相关性的更微观解释方面取得重大而迅速的进展。更广泛的影响：对堵塞的颗粒物质如何开始流动的更基本的理解可能会导致这些系统的加工、运输和存储方面的进步，其中包括很大一部分工业原材料、食品和药品。具体的进展可能包括：1)防止堆积的颗粒介质即使在长时间储存后也发生灾难性的破坏；2)优化土壤沉降的土木工程程序；以及3)更好地了解用于纳米技术应用的高度粘合的堵塞纳米颗粒。通过这个项目，我们将培训新的科学家使用几种强大的实验技术，如共焦显微镜、X射线断层扫描和FRET。我们还将开发演示材料，以非常直观的方式突出颗粒流的复杂和意想不到的特性。这些演示将用于本科课程、实验室开放参观和公开讲座，向可能不熟悉颗粒材料的观众演示颗粒材料的迷人特性。我们将大力鼓励本科生参与拟议的研究，例如，计算项目是本科生的理想选择，他们拥有基本的计算机编程知识，可以立即开始运行现有的MD模拟和分析数据。最后，我们将采取措施减少物理和工程专业学生之间存在的种族和性别失衡。两家私人投资机构都将积极招募妇女和代表性不足的少数群体参加各自的方案。CO将通过在研究生招生委员会任职来为耶鲁工程和应用科学项目做到这一点。CO还将指导耶鲁大学面向少数族裔学生的科学、技术和研究学者计划的本科生，WL将指导华盛顿特区地区的少数族裔高中和本科生。

ABSTRACT-0456703-0457431Yale UniversityCollaborative Research: Studies of aging and memory in granular materialsW. Losert (Department of Phyiscs, IPST, and IREAP, University of Maryland),C.S. O.Hern, (Departments of Mechanical Engineering and Physics, Yale University)We seek a deeper understanding of aging and memory in jammed granular materials. Our research focus is on the structure, slow evolution and initial failure of the jammed state. We will use novel 3D imaging techniques of individual grains and complementary molecular dynamics (MD) simulations to study the slow evolution of the grain-scale properties of granular materials under shear stress. We believe that the results from these studies can be used to build better models for yielding and the initiation of flow in jammed granular systems.Intellectual Merit: Few studies have been able to analyze the arrangements of individual grains during the aging process in granular materials. This largely results from the fact that non-invasive and nondestructive techniques for locating the positions of grains in 3D are only now available. We will use several state-of-the-art techniques to study the microstructure during aging: confocal microscopy and fluorescence resonance energy transfer (FRET) at the University of Maryland and synchrotron x-ray microtomography at the European Synchrotron Radiation Facility in Grenoble, France. Prof. Wolfgang Losert (WL) will conduct the experiments in collaboration with Profs. Renaud Delannay (Rennes) and Doug English (Maryland). Prof. Corey O.Hern (CO) will perform MD simulations of simple models of frictional granular materials to guide future experiments, investigate the stability of experimentally obtained jammed configurations, and probe parameter regimes that are not easily accessed by experiments. CO has extensive experience in simulations of athermal systems and access to ample computational resources. The proposed collaboration between simulation and experiment will allow us to make significant and swift progress in developing a more microscopic explanation of aging and history dependence in granular materials.Broader Impact: An improved fundamental understanding of how jammed granular matter starts to flow may lead to advances in the processing, transport, and storage of these systems, which includes a large fraction of industrial raw materials, food, and pharmaceutical products. Specific advances may include 1) prevention of catastrophic failure of heaps of granular media even after prolonged storage, 2) optimized civil engineering procedures for the settling of soil, and 3) a better understanding of highly cohesive jammed nanoparticles for nanotechnology applications. Through this project we will train new scientists to use several powerful experimental techniques such as confocal microscopy, x-ray tomography, and FRET. We will also develop demonstration materials to highlight the complex and unexpected properties of granular flows in very visual ways. These demos will be used in undergraduate courses, lab open houses, and public lectures to demonstrate the fascinating properties of granular materials to audiences that may not be familiar with them. We will strongly encourage undergraduate student involvement in the proposed research, e.g. the computational projects are ideal for undergraduates, who, with a basic knowledge of computer programming can begin immediately running existing MD simulations and analyzing data. Lastly, we will take steps to reduce the racial and gender imbalance that exists among students in physics and engineering. Both PIs will actively recruit women and underrepresented minorities into their respective programs. CO will do so for the Yale Engineering and Applied Science program by serving on the Graduate Admissions Committee. CO will also mentor undergraduate students from the Science, Technology and Research Scholars program for minority students at Yale and WL will mentor minority high school and undergraduate students in the Washington, DC area.