Shear Jamming, Diffusion, Reversibility, Anisotropy, and Fluctuations in Dense Granular Materials

致密颗粒材料中的剪切干扰、扩散、可逆性、各向异性和波动

• 批准号: 1206351
• 负责人: Robert Behringer
• 金额: $ 67万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206351&HistoricalAwards=false
• 关键词: Shear; Jamming; Diffusion; Reversibility; Anisotropy

****Technical Abstract****This project involves novel experiments to understand the dynamical, static and statistical properties of granular materials near jamming. These materials are of great technical importance, yet their properties remain poorly understood. The Duke group and collaborators at Brandeis, recently showed that near-jamming properties of frictional granular systems are much richer than previously thought, and exhibit an order-disorder transition, shear jamming, involving complex networks of contacts and forces. This project explores these networks, the physical processes involved in their formation, and the impact that these networks and processes have on static and dynamical granular properties. Experiments in two and three dimensions, using novel photoelastic and laser scanning techniques, will address several issues: 1) structural and mechanical properties of granular materials near shear jamming and their dynamical response to strain; 2) the role of friction in shear jamming; 3) variables needed for a good statistical characterization of states near jamming; 4) particle dynamics, diffusive motion, and time scales near (shear) jamming; 5) near-jamming rheological response of granular material; 6) differentiation in the structure and response of 3D vs. 2D granular systems. Post-docs, Ph.D. students and undergraduates will be actively involved at all stages of research. The PI, post-docs and students will be actively involved in outreach to elementary and middle schools.****Non-Technical Abstract****Sand, cereal, salt, and pills are commonplace examples of a special type of matter, granular materials. Besides being part of daily life, granular materials, e.g. coal, grain, plastic feed stock, among many others, form a large part of our economy. They have properties that are both fascinating and poorly understood. Under the right conditions, they flow like a fluid, but they also can become solid and support weight. The fluid-like to solid-like transition is particularly important for practical applications, and it is the focus of the present project which focuses on fundamental questions. The solid granular state is controlled by networks of inter-grain contacts. In recent work, the PI and collaborators at Brandeis showed that these networks, which control the fluid-solid jamming transition, have much richer and more novel properties than was previously thought. This project seeks to understand the mechanisms leading to the formation of the networks, and the impact that these mechanisms have on both fluid and solid granular states. This project integrates training at all levels. Ph.D. students and post-docs learn by leading research projects. Undergraduate and high school students routinely participate via related projects. The PI, Ph.D. students and post-docs are actively involved in outreach involving elementary and middle school students. The PI is also actively involved with technology transfer through interactions with industrial users of granular materials, for instance through the International Fine Particle Research Institute.

*技术摘要*这个项目包括一些新颖的实验，以了解颗粒材料在干扰附近的动态、静态和统计特性。这些材料在技术上非常重要，但人们对它们的性质知之甚少。DUKE小组和Brandeis的合作者最近发现，摩擦颗粒系统的近干扰特性比之前认为的要丰富得多，并表现出一种有序-无序的转变，即剪切干扰，涉及复杂的接触和力网络。这个项目探索了这些网络，它们形成过程中涉及的物理过程，以及这些网络和过程对静态和动态颗粒性的影响。利用新颖的光弹性和激光扫描技术进行的二维和三维实验将解决几个问题：1)剪切干扰附近颗粒材料的结构和机械特性及其对应变的动态响应；2)摩擦在剪切干扰中的作用；3)良好统计表征干扰附近状态所需的变量；4)颗粒动力学、扩散运动和(剪切)干扰附近的时间尺度；5)颗粒材料的近干扰流变响应；6)3D和2D颗粒系统的结构和响应的差异。博士后、博士后和本科生将积极参与研究的各个阶段。PI、博士后和学生将积极参与到小学和中学的宣传活动。*非技术摘要*沙、谷物、盐和药丸是一种特殊类型的物质-颗粒材料的常见例子。除了作为日常生活的一部分，煤炭、谷物、塑料原料等颗粒材料也构成了我们经济的一大部分。它们的特性既令人着迷，又鲜为人知。在适当的条件下，它们像流体一样流动，但它们也可以变成固体并支撑重量。类流体到类固体的转变在实际应用中尤为重要，也是本课题关注的焦点问题。固体颗粒态由晶间接触网络控制。在最近的工作中，PI和Brandeis的合作者表明，这些控制流固干扰转变的网络具有比之前认为的更丰富和更新颖的特性。这个项目试图了解导致网络形成的机制，以及这些机制对流体和固体颗粒状态的影响。该项目整合了所有级别的培训。博士生和博士后通过领先的研究项目学习。本科生和高中生经常通过相关项目参与。PI、博士后和博士后积极参与涉及中小学生的外联活动。通过与颗粒状材料的工业用户进行互动，例如通过国际精细颗粒研究所，该研究所还积极参与技术转让。