Static and Dynamic Response of Particulate Media

颗粒介质的静态和动态响应

• 批准号: 0828359
• 负责人: Leonardo Silbert
• 金额: $ 23.6万
• 依托单位: Southern Illinois University at Carbondale
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0828359&HistoricalAwards=false
• 关键词: Static; Dynamic; Response; Particulate; Media

CBET-0828359SilbertA sandpile is possibly the simplest and the most common concept of a mechanically stable, granular packing, yet one that exhibits strongly non-linear and complex behavior. A basic understanding of the relation between the microscopic distribution of contact stresses at the grain scale, to bulk, macroscopic, mechanical stability and material strength, persists as one of the most fundamentally challenging questions in contemporary granular matter research. This proposal implements three-dimensional computer simulations of granular materials to address several key features of the mechanical stability of granular packings subject to static and dynamic perturbations. (i) Validate the simulations by comparing results with available experimental data. (ii) Compute linear response profiles in ordered and disordered packings that conclusively resolves the dispute between competing theories of stress transmission based on isotropic/anisotropic elasticity and wave-like propagation models. (iii) Study response crossover effects in small and large packings and correlate this phenomena to emerging length scales that control the stress response. (iv) Determine how friction influences mechanical stability over the range of stable packing fractions, from the close-packed limit down to random loose packing. Compare how different packings approach the onset of failure - loss of mechanical rigidity - with increasing perturbation magnitude, and measure dynamic response of intruder probe particles flowing through the packing. Novel aspects of this work build on current experimental and theoretical results for non-cohesive grains, to include cohesive forces, complex particle shapes, and hydrodynamic effects such as slurries. Intellectual Merit: Fundamental description of the mechanisms of stress transmission inside granular packings, relating how microstructural properties at the grain scale determine macroscopic behavior. Extend our current knowledge on non-cohesive sphere packings, to new and novel systems that include cohesive powders and adhesive grains, composites, and slurries. Broader Impact: Granular materials are found in a wide variety of industrial, natural, and technological settings, and the research has a broad appeal as this study belongs to a large class of problems concerned with mechanical rigidity in amorphous materials including colloidal dispersions, glasses, and polymer and biological networks. Participating students will be encouraged to develop an understanding of these broader aspects of the research. Undergraduate and graduate students are well-suited to the research, and will gain experience in state-of-the-art simulation techniques, computer cluster management, and/or development of computational algorithms, which will be made available as open source software. Simulation configurations, results, and visualizations will be added to a website for collaborative research and public use. Dissemination of research results will follow from publication in refereed journals and attendance at meetings in the physics and engineering communities, and visits to collaborative institutions. The PI continues to implement simulation aides into undergraduate classes and is requesting funds for demonstration materials for class instruction, and future public speaking events. The PI actively promotes the general vision of the department and institution for involving under-represented groups in research, particularly in the physical sciences, and continues to support the recently developed PhD program in the department.

CBET-0828359Silberta sandpile可能是机械稳定，颗粒状堆积的最简单，最常见的概念，但表现出强烈的非线性和复杂行为。对接触应力在晶粒尺度上的显微镜分布与批量，宏观，机械稳定性和材料强度之间的微观分布之间的关系的基本理解一直是当代粒状物质研究中最具挑战性的问题之一。该提案实施了三维计算机模拟颗粒材料的模拟，以解决颗粒包装的机械稳定性的几个关键特征，但受到静态和动态扰动的影响。 （i）通过将结果与可用的实验数据进行比较来验证模拟。 （ii）计算有序和无序填料中的线性响应曲线，这些构图最终解决了基于各向同性/各向异性弹性和波浪样繁殖模型的竞争压力传播理论之间的争议。 （iii）研究小包装和大包装的响应跨界效应，并将这种现象与控制应力反应的新兴长度尺度相关联。 （iv）确定摩擦如何影响稳定堆积分数范围内的机械稳定性，从近距离填充的极限到随机松动堆积。比较不同的填料如何接近故障的开始 - 机械刚度的丧失 - 随着扰动的幅度的增加，并测量流过整个包装的入侵者探针颗粒的动态响应。这项工作的新方面基于非粘性晶粒的当前实验和理论结果，包括凝聚力，复杂的颗粒形状和水动力效应，例如浆液。智力优点：颗粒包装内部压力传播机制的基本描述，将微观结构特性在谷物尺度上如何确定宏观行为。将目前的知识扩展到包括粘性粉末和粘合剂颗粒，复合材料和浆液的新系统和新型系统。更广泛的影响：在各种工业，自然和技术环境中都发现了颗粒状材料，并且该研究具有广泛的吸引力，因为本研究属于与机械刚性有关的大量问题，这些问题在无定形材料中，包括胶体分散体，眼镜，聚合物和生物网络。将鼓励参与的学生了解研究的这些更广泛的方面。本科生和研究生非常适合研究，并将获得最先进的仿真技术，计算机群集管理和/或计算算法的开发的经验，这些算法将作为开源软件提供。仿真配置，结果和可视化将添加到网站上，以进行协作研究和公众使用。研究结果的传播将随之而来的是在裁判期刊上的出版物，并参加了物理和工程社区的会议，并参观了协作机构。 PI继续将仿真助手实施到本科课程中，并要求资金用于班级教学和未来的公开演讲活动。 PI积极促进部门和机构的一般愿景，即参与研究不足的群体，特别是在物理科学领域，并继续支持该部门最近开发的博士学位计划。