Experiments on Granular Materials and Crumpled Sheets

非技术性这个项目寻求扩大我们对远未处于平衡状态的系统的理解。实验集中在这类系统的两个普遍存在的例子上：颗粒介质和皱缩的弹性薄片。颗粒介质，如沙子或粉末，是由大量的单个颗粒组成的。同样，一张皱巴巴的纸(例如纸)是由由折痕分隔的平面组成的。我们试图了解每一种组成颗粒的性质，以及它们的大量集合(纸张中的颗粒、脊)的性质是如何确定的。例如，我们将研究皱巴巴的薄片中的脊线网络如何在原本松软的系统上赋予刚性。我们将研究如何在某些条件下将大量沙粒填充成固体形式，并在其他条件下像液体一样流动。大学本科生。马萨诸塞州大学、阿默斯特学院和该地区的其他学院将在新项目的探索工作中发挥关键作用。研究生将接触到各种各样的实验技术。此外，课程材料也具有重要的工业意义，将使学生接触到重要的应用问题。技术：本项目涉及两个典型的非平衡系统的实验研究-颗粒介质和皱缩的弹性薄片。颗粒介质是由颗粒组成的，颗粒通过耗散的接触相互作用而相互作用。褶皱薄板是由由折痕分隔的小平面组成的，这两个小平面都是非线性的局部弹性单元。在这两个系统中，组成元素都是宏观的，因此不受热波动的影响。这项研究试图确定控制这种远离平衡的系统的相行为、涨落、整体响应和结构的一般原则。为此，我们在实验上探索了与测量的线性响应相关的波动，并表征了颗粒的有序和无序排列。大学本科生。马萨诸塞州大学、阿默斯特学院和该地区的其他学院将在新项目的探索工作中发挥关键作用。研究生将接触到许多技术，包括高速视频成像、共焦显微镜、扩散光散射、声学和机械响应技术以及表面散斑干涉技术。所要学习的材料也具有重要的工业意义，将使学生能够接触到重要的应用问题。

Non-technicalThis project seeks to extend our understanding of systems that are far from being in equilibrium. The experiments focus on two ubiquitous examples of such systems: granular media and crumpled elastic sheets. Granular media, such as sand or powders, are made up of a large number of individual grains. Likewise, a crumpled sheet (of paper, for example) is made up of flat facets delimited by creases. We seek to understand the properties of each of the constituent grains and how the properties of a large collection of them (grains, ridges in paper) are determined. For example, we will study how the network of ridges in a crumpled sheet confers rigidity on an otherwise floppy system. We will study how a large collection of sand grains can, under some conditions, pack into a solid form and flow like a liquid under other conditions. Undergraduate students from Univ. of Massachusetts, Amherst and other colleges in the area, will play a crucial role in exploratory work on new projects. Graduate students will gain exposure to a wide variety of experimental techniques. Furthermore, the subject materials are also industrially important and will give the students access to important applied problems.Technical:This project involves experimental studies of two archetypal non-equilibrium systems - granular media and crumpled elastic sheets. Granular media are made up of grains that interact by dissipative contact interactions. A crumpled sheet is made up of facets delimited by creases, both of which are nonlinear, localized elastic elements. In both systems the constituent elements are macroscopic, and therefore are not subject to thermal fluctuations. The research seeks to identify general principles governing phase behavior, fluctuations, bulk response and structure of such far-from-equilibrium systems. To this end, fluctuations are experimentally probed, related to measured linear response, and ordered and disordered arrangements of particles are characterized. Undergraduate students from the Univ. of Massachusetts, Amherst and other colleges in the area will play a crucial role in the exploratory work on new projects. Graduate students will gain exposure to many techniques - including high-speed video imaging, confocal microscopy, diffusive light scattering, acoustic and mechanical response techniques, and surface speckle interferometry. The materials to be studied are also industrially important and will give the students access to important applied problems.