Structural rearrangements and transport properties of cyclically sheared granular packings

循环剪切颗粒填料的结构重排和输运特性

• 批准号: 0853943
• 负责人: Arshad Kudrolli
• 金额: $ 30.01万
• 依托单位: Clark University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-15 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0853943&HistoricalAwards=false
• 关键词: Structural; rearrangements; transport; properties; cyclically

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0853943KudrolliIntellectual Merit The PI proposes to apply a state of the art fluorescent index matching technique to measure the three dimensional positions of particles in the bulk to investigate the elastic and plastic response of a dense granular system undergoing cyclic shear. The proposed research will be transformative because it allows one to systematically examine the packing structure and transport coefficients of the particles over a volume fraction ranging from random loose packing to hexagonal close packings in a regime which is most common to industrial applications. There is a need for such a study because athermal granular matter lacks a sound hydrodynamic description in spite of their preponderance in industrial processes leading to ad hoc solutions. The proposed work builds on preliminary experiments where it is found that velocity auto correlation function for sheared dense granular media show a fast decay, which raises the possibility that hydrodynamic calculations can be extended to significantly greater range of volume fractions compared with elastic hard sphere liquids at equilibrium. A cyclic shear cell apparatus is developed, and a broad shear zone is obtained in the bulk. Three dimensional particle tracking allows one to measure nearest neighbor distribution, the icosahedral order parameter, besides the Voronoi volume distribution as a function of volume fraction and strain, much in the way this is being accomplished in colloidal glasses with confocal microscopy, but here at a 100 times larger scale. Such information can reveal fundamental assumptions about granular systems and understanding of their properties in relation to other particulate matter such as colloidal glasses and suspensions, besides help develop a computational model. The cyclic and quasi static nature of the shear application, will allow us to identify parameters over which one can experience an elastic response in finite, rigid multi contact particulate systems. Furthermore, once plastic deformation has occured, detect heterogenities, identify irrevisible shear transformation zones and determine their topology. Then, the PI will investigate the effect of polydispersity on granular packing and transport properties. It is well know that particulates segregate even if minor differences between them exist. In particular, we will examine the motion of an intruder particle in a cyclically sheared system and study the competition between size, roughness, density and gravity. The application of the fluctuation-dissipation principle to their motion will be tested. The comparison with theoretical calculations will be conducted in collaboration with Professor V. Kumaran of the Department of Chemical Engineering at the Indian Institute of Sciences, Bangalore. Further, the PI proposes to build a database downloadable from the web, containing the trajectories of all the particles as a function of shear cycle that other members in the field can use to carry out their own analysis.Broader Impact The proposed work will have significant impact on undergraduate, graduate and post doctoral student training, besides fostering international collaborations. The involvement of underrepresented members in STEM careers will be positively impacted because the graduate student working on the project is female, and the post doctoral student has partial African heritage. The grant will enhance summer research experience of undergraduate students and help accomplish their honor thesis projects in the laboratory. Aspects of the research will be also adapted into a course on mechanics currently being developed by the PI.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。0853943 Kudrolli智力功绩PI建议应用最先进的荧光指数匹配技术来测量散装颗粒的三维位置，以研究经历循环剪切的致密颗粒系统的弹性和塑性响应。拟议的研究将是变革性的，因为它允许一个系统地检查的包装结构和传输系数的颗粒的体积分数范围从随机松散包装的六角形紧密包装的制度，这是最常见的工业应用。有必要进行这样的研究，因为无热颗粒物质缺乏一个健全的流体动力学描述，尽管他们在工业过程中的优势，导致特设的解决方案。 拟议的工作建立在初步实验中，发现剪切致密颗粒介质的速度自相关函数显示出快速衰减，这提高了流体动力学计算的可能性，可以扩展到显着更大的范围内的体积分数相比，弹性硬球液体平衡。研制了循环剪切池装置，在块体中获得了较宽的剪切带。三维粒子跟踪允许一个测量最近邻分布，二十面体序参数，除了作为体积分数和应变的函数的Voronoi体积分布，这是在胶体玻璃与共聚焦显微镜，但在这里在100倍更大的规模完成的方式。这些信息可以揭示有关颗粒系统的基本假设，并了解其与其他颗粒物质（如胶体玻璃和悬浮液）的性质，此外还有助于开发计算模型。循环和准静态性质的剪切应用，将使我们能够识别参数，其中一个可以经历一个弹性响应，在有限的，刚性的多接触颗粒系统。此外，一旦发生塑性变形，检测不均匀性，识别不可见的剪切转换区，并确定其拓扑结构。 然后，PI将研究多分散性对颗粒填充和传输性能的影响。众所周知，即使微粒之间存在微小差异，它们也会分离。特别是，我们将研究入侵粒子在循环剪切系统中的运动，并研究尺寸，粗糙度，密度和重力之间的竞争。将检验波动耗散原理在它们运动中的应用。 将与班加罗尔印度科学研究所化学工程系V. Kumaran教授合作进行与理论计算的比较。此外，PI还建议建立一个可从网上下载的数据库，该数据库包含所有粒子的轨迹作为剪切周期的函数，该领域的其他成员可以使用该数据库进行自己的分析。更广泛的影响除了促进国际合作外，拟议的工作将对本科生、研究生和博士后的培养产生重大影响。 参与STEM职业的代表性不足的成员将受到积极影响，因为参与该项目的研究生是女性，博士后学生有部分非洲遗产。该补助金将提高本科生的夏季研究经验，并帮助他们完成他们的荣誉论文项目在实验室。研究的各个方面也将被改编成目前正在由PI开发的力学课程。