Collaborative Research: Visualizing the Aging Process in Granular Matter Using Experiment and Simulation

提案编号：0625890和0625149主要研究者：Losert， Wolfgang和O'Hern, Corey s.隶属机构：马里兰大学学院公园分校和耶鲁大学提案标题：合作研究：利用实验和模拟可视化颗粒物质的老化过程智力价值这个项目的目标是在实验和模拟中研究一个被卡住的三维粒子系统如何在响应施加的力时缓慢地重新排列。衰老和记忆会影响在何种压力下，一堆堵塞的粒子会开始流动，以及如何流动。对堵塞颗粒物质如何开始流动的基本理解的改进可能会导致这些系统的加工、运输和存储方面的进步，这些系统包括很大一部分工业原料、食品和药品。具体的进展可能包括：1)防止颗粒状介质堆在长时间储存后发生灾难性破坏；2)优化土木工程程序以使土壤沉降；3)更好地理解用于纳米技术应用的高粘性堵塞纳米颗粒。颗粒物质的老化伴随着显著的蠕变或足够大的压实，从而导致颗粒接触网络中的重排。虽然存在由蠕变和单个颗粒接触强化引起的微观老化模型，但这些模型并不能解释接触网络中的这种变化。该项目将试图了解重排事件如何导致大块材料性能的变化，以及这是否可以成为真实材料老化过程中的主导模式。提出的方法是直接成像三维粒子重排，并将粒子运动与模拟中观察到的动力学（其中可以引入不同的老化规律）在相同的力下进行比较。3D排列将使用两种最先进的技术成像，提供流体浸没和干颗粒物质的信息：流体浸没颗粒物质的激光片扫描允许系统扫描大数据量。x射线同步加速器显微断层成像允许干燥颗粒物质成像。一种来自生物学的新方法，荧光共振能量转移（FRET），将用于直接确定接触网络的关键特征。更广泛的影响关于老化过程中三维粒子重排的实验数据将在一个网站上提供，以便与其他进行老化实验、数值或理论工作的人进行比较。通过这个项目，新的科学家将被训练使用强大的实验技术——共聚焦显微镜、x射线断层扫描、FRET和最先进的模拟。在欧洲同步加速器采集同步加速器数据将增加学生的国际经验。示范材料也将开发，以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、大学开放日和公开讲座。强烈鼓励本科生参与拟议的研究。

Proposal Numbers: 0625890 and 0625149Principal Investigators: Losert, Wolfgang and O'Hern, Corey S.Affiliations: University of Maryland College Park and Yale UniversityProposal Title: Collaborative Research: Visualizing the aging process in granular matter using experiment and simulationIntellectual merit The goal of this project is to investigate in experiment and simulation how a jammed three dimensional system of particles slowly rearranges in response to applied forces. Aging and memory affect under what forcing a jammed arrangement of particles will start to flow, and how it will flow. 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.Aging in granular matter is accompanied by notable creep or compaction large enough to cause rearrangements in the particle contact network. While microscopic models of aging due to creep and strengthening of individual particle contacts exist, these models do not account for such changes in the contact network. This project will attempt to understand how rearrangement events can lead to changes in bulk material properties and whether this can be the dominant mode in the aging process in a real material.The proposed approach is to directly image three dimensional particle rearrangements, and to compare particlemotion with dynamics observed in simulation (where different aging laws can be introduced) under the same forcing. 3D arrangements will be imaged using two state-of-the-art techniques which provide information about fluid immersed and dry granular matter: laser sheet scanning of fluid immersed granular matter allows for systematic scans of large data volumes. x-ray synchrotron microtomography permits imaging of dry granular matter. A new approach from biology, fluorescence resonance energy transfer (FRET), will be used to determine key features of the contact network directly.Broader ImpactThe experimental data on 3D particle rearrangements during aging will be made available on a website for comparison to others carrying out experimental, numerical, or theoretical work on aging. Through this project new scientists will be trained to use powerful experimental techniques - confocal microscopy, x-ray tomography, and FRET and state of the art simulations. Synchrotron data taking at the European synchrotron will add to the student international experience. Demonstration materials will also be developed to highlight the complex and unexpected properties of granular flows. These demos will be used in undergraduate courses, university open houses, and public lectures. Undergraduate student involvement in the proposed research will strongly be encouraged.