Dynamic Contact Networks in Granular Systems: New Insights into Fracture &Segregation

颗粒系统中的动态接触网络：对断裂的新见解

• 批准号: 0907146
• 负责人: Wolfgang Losert
• 金额: $ 34.5万
• 依托单位: University of Maryland, College Park
• 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: 2009-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907146&HistoricalAwards=false
• 关键词: Dynamic; Contact; Networks; Granular; Systems

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).****NON-TECHNICAL ABSTRACT****Understanding how and when particulate matter such as sand or gravel will respond to stress and start to flow is an important problem in a wide range of fields such as earthquake prediction, rock avalanche hazard prediction, and civil engineering. This project will study the flow of granular matter by looking at the networks of contact points between particles, and examining how these networks change as the granular material flows. Other approaches to understand granular flow focus on the motion of individual particles or look at the system as a fluid-like continuum. The proposed research will apply the tools of network theory, which will highlight the intermediate scale ? ensembles of touching particles - and will thus provide a novel perspective on granular flow. The project will focus on two key processes that occur in granular materials, the breaking of the contact network during flow of granular material, and the segregation of particles by size in such a granular flow. The proposed research will train graduate students in state of the art experimental and computational research and in mentoring of undergraduate and high school students. The research team will also conduct public demonstrations of their work, highlighting -on simple examples- flows of sand that possesses fascinating, technologically important properties which are not yet fully understood.****TECHNICAL ABSTRACT****The goal of this project is to measure three dimensional granular flow fields experimentally, and to utilize network theory to characterize the flow behavior. Network theory metrics focus on the large scale structure of ensembles of linked objects. Since granular matter derives its strength from a dense network of particle contacts, network theory will provide a novel viewpoint relevant to understanding granular materials properties. The focus will be on two key granular flow processes ? fracture and segregation. The first goal is to characterize the onset of fracture of a jammed granular material, i.e. the formation of large scale structural rearrangements such as shear zones when granular matter starts to flow. Understanding how and when granular matter will fracture and start to flow is important to a wide range of fields such as earthquake prediction, rock avalanche hazard prediction, and civil engineering. The second goal is to characterize the particle rearrangements that lead to segregation of a mixture of particle sizes during granular flows. Graduate students will be trained in a unique combination of experimental tools (3D imaging) and theoretical concepts (network theory), and will contribute to mentoring of undergraduate students. The group has developed demonstrations that highlight the most striking features of jamming and granular segregation, which will be presented at public lectures and outreach events.

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。非技术性摘要 * 在地震预测、岩崩灾害预测、土木工程等广泛的领域中，了解砂或砾石等颗粒物质如何以及何时响应于应力而开始流动是一个重要的问题。 这个项目将通过观察颗粒之间的接触点网络来研究颗粒物质的流动，并检查这些网络如何随着颗粒物质的流动而变化。 其他理解颗粒流的方法集中在单个颗粒的运动上，或者将系统视为类似流体的连续体。 拟议的研究将适用于网络理论的工具，这将突出中间规模？接触颗粒的合奏，并因此将提供一个新的角度对颗粒流。 该项目将重点关注颗粒材料中发生的两个关键过程，即颗粒材料流动过程中接触网络的断裂，以及颗粒在这种颗粒流中按尺寸的分离。 拟议的研究将培养研究生在国家的最先进的实验和计算研究，并在本科生和高中生的辅导。 研究小组还将对他们的工作进行公开演示，以简单的例子强调具有迷人的、技术上重要的特性的沙流，这些特性尚未完全了解。技术摘要 * 本项目的目标是通过实验测量三维颗粒流场，并利用网络理论来表征流动行为。 网络理论度量集中在大规模结构的合奏链接对象。 由于颗粒物质的强度来自于颗粒接触的密集网络，网络理论将为理解颗粒物质的性质提供一个新的观点。 重点将放在两个关键的颗粒流过程？断裂和偏析。 第一个目标是表征堵塞的颗粒材料的断裂的开始，即当颗粒物质开始流动时形成大规模的结构重排，例如剪切区。 了解颗粒物质如何以及何时破裂并开始流动对地震预测、岩石雪崩危险预测和土木工程等广泛领域都很重要。 第二个目标是表征颗粒重排，导致分离的颗粒尺寸的混合物在颗粒流。 研究生将接受实验工具（3D成像）和理论概念（网络理论）的独特组合的培训，并将有助于指导本科生。 该小组已经开发了突出干扰和颗粒隔离最显著特征的演示，将在公开讲座和外联活动中展示。