Deformation and Fracture of Disordered Solids: Mechanisms Underlying Macroscopic Behavior

无序固体的变形和断裂：宏观行为的机制

• 批准号: 1006805
• 负责人: Mark Robbins
• 金额: $ 58万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006805&HistoricalAwards=false
• 关键词: Deformation; Fracture; Disordered; Solids; Mechanisms

TECHNICAL SUMMARYThis award supports theoretical and computational research and education on the deformation and fracture of disordered solids to determine the microscopic mechanisms underlying macroscopic mechanical response. One focus will be the failure modes of amorphous polymers. Here chain connectivity leads to unusual modes of deformation, including craze formation, necking and pronounced strain hardening. A second focus will be general scaling behavior during steady, quasistatic shear or compression of disordered solids.Traditional engineering models of plastic deformation and fracture are based on macroscopic continuum equations with phenomenological constitutive relations for the spatially averaged response. Experiments provide limited information about the microscopic origins of this response. The PI will perform simulations to provide new insight into the connection between macroscopic mechanics and molecular scale interactions and deformation mechanisms. The connectivity of polymer molecules leads to topological entanglements. Most models of the mechanical properties of amorphous polymers assume that these entanglements act like chemical crosslinks. Tracking the motion of entanglements during deformation will provide a detailed test of these models and new information to serve as a foundation for improving them. The effect of polymer structure and molecular friction on entanglements, stress-strain relations and mode of failure will be studied. Studies of entanglements at polymer interfaces will provide microscopic understanding of polymer welds and friction forces between polymers. Studies of sheared systems have played an important role in developing new understanding of non-equilibrium behavior. Simulations will explore scaling behavior in quasistatic shear or compression of disordered systems. Systems evolve through a series of earthquake like events with a power law distribution of sizes. The scaling and spatio-temporal dynamics of individual events, the conditions that nucleate them, and their correlations over long times and distances will be studied. Specific issues will be how inertia and irreversible damage affect non-equilibrium critical phenomena.This project will contribute to the twenty first century workforce by training students in a wide range of interdisciplinary modeling and computational methods. This training will extend beyond the students supported by the grant to students associated with a local IGERT on "Modeling Complex Systems." A new course on multiscale modeling will be developed in coordination with the IGERT. The course will be aimed at science and engineering students from a range of disciplines and course materials will be shared on the web. Outreach efforts will bring research results to a wider audience in partnership with Johns Hopkins based outreach programs for K-12 students, including the Physics Fair, Youth for Astronomy and Engineering, and the Center for Talented Youth. Animations and web-based modules for demonstrating concepts related to the grant will be developed. Recruitment of new students will be done in collaboration with the above IGERT, which is partnering with women's colleges and other universities with a high percentage of students from underrepresented groups.NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education to better understand how materials deform in response to applied stress. The research will focus on materials made from long chain-like molecules that are entangled with each other. The PI aims to perform computer simulations of these amorphous polymer materials to understand how they respond to mechanical stress at a molecular level. The research should elucidate how the chains are tangled and the way that the entanglement changes in a precise mathematical sense.This research addresses fundamental processes that impact many technologies. One thrust will examine general aspects of deformation and fracture that may be relevant to the strength and failure of engineered and natural materials on laboratory and tectonic scales. Another will explore specialized behavior in amorphous polymers that affects their function as adhesives, structural materials, and solid lubricants. An improved understanding of the above systems will aid the design and modeling of structural components and the development of tailored materials with improved properties. The research projects will also serve as a testing ground for new computational modeling techniques that couple very different descriptions of materials. These approaches have the potential to improve modeling of a broad range of complex materials behavior beyond the specific projects addressed in this project. This project will contribute to the twenty first century workforce by training students in a wide range of interdisciplinary modeling and computational methods. This training will extend beyond the students supported by the grant to students associated with a local IGERT on "Modeling Complex Systems." A new course on multiscale modeling will be developed in coordination with the IGERT. The course will be aimed at science and engineering students from a range of disciplines and course materials will be shared on the web. Outreach efforts will bring research results to a wider audience in partnership with Johns Hopkins based outreach programs for K-12 students, including the Physics Fair, Youth for Astronomy and Engineering, and the Center for Talented Youth. Animations and web-based modules for demonstrating concepts related to the grant will be developed. Recruitment of new students will be done in collaboration with the above IGERT, which is partnering with women's colleges and other universities with a high percentage of students from underrepresented groups.

该奖项支持无序固体变形和断裂的理论和计算研究和教育，以确定宏观机械响应的微观机制。一个焦点将是无定形聚合物的失效模式。在这里，链的连通性会导致不寻常的变形模式，包括银纹形成、颈缩和明显的应变硬化。第二个重点是无序固体在稳态、准静态剪切或压缩过程中的一般标度行为。传统的塑性变形和断裂工程模型是基于宏观连续方程和空间平均响应的唯象本构关系。关于这种反应的微观起源，实验提供的信息有限。PI将进行模拟，以提供宏观力学和分子尺度相互作用和变形机制之间的联系的新见解。聚合物分子的连接性导致拓扑缠结。大多数无定形聚合物力学性质的模型都假设这些缠结的作用类似于化学交联。跟踪变形过程中缠结的运动将为这些模型提供详细的测试和新的信息，作为改进它们的基础。将研究聚合物结构和分子摩擦对缠结、应力-应变关系和失效模式的影响。在聚合物界面缠结的研究将提供微观的理解聚合物之间的聚合物焊接和摩擦力。剪切系统的研究在发展对非平衡行为的新认识方面发挥了重要作用。模拟将探索无序系统准静态剪切或压缩的标度行为。系统通过一系列类似地震的事件演化，其大小呈幂律分布。将研究单个事件的尺度和时空动态、使它们成核的条件以及它们在长时间和长距离上的相互关系。具体问题将是如何惯性和不可逆的损害影响非平衡临界现象。这个项目将有助于通过培训学生在广泛的跨学科建模和计算方法的21世纪的劳动力。这项培训将超出学生资助的范围，扩大到与当地IGERT有关的“复杂系统建模”学生。“将与IGERT协调开发一个关于多尺度建模的新课程。该课程将针对来自一系列学科的理工科学生，课程材料将在网络上共享。 外联工作将与约翰霍普金斯为K-12学生提供的外联计划合作，将研究成果带给更广泛的受众，包括物理博览会，天文学和工程青年以及青年人才中心。将制作动画和网络模块，展示与赠款有关的概念。IGERT与女子学院和其他大学合作，招收来自弱势群体的学生比例很高。非技术性总结该奖项支持理论和计算研究和教育，以更好地了解材料如何变形，以应对施加的压力。这项研究将集中在由长链状分子相互纠缠制成的材料上。PI旨在对这些无定形聚合物材料进行计算机模拟，以了解它们如何在分子水平上对机械应力做出反应。这项研究应该阐明链是如何纠缠在一起的，以及纠缠在精确数学意义上的变化方式。这项研究涉及影响许多技术的基本过程。其中一个重点将研究变形和断裂的一般方面，这些方面可能与实验室和构造尺度上的工程和天然材料的强度和失效有关。另一个将探索非晶聚合物的特殊行为，影响其作为粘合剂，结构材料和固体润滑剂的功能。对上述系统的进一步理解将有助于结构部件的设计和建模以及具有改进性能的定制材料的开发。这些研究项目还将作为新的计算建模技术的试验场，这些技术将非常不同的材料描述结合在一起。这些方法有可能改善本项目中涉及的特定项目之外的广泛复杂材料行为的建模。这个项目将有助于二十一世纪的劳动力培训学生在广泛的跨学科建模和计算方法。这项培训将超出学生资助的范围，扩大到与当地IGERT有关的“复杂系统建模”学生。“将与IGERT协调开发一个关于多尺度建模的新课程。该课程将针对来自一系列学科的理工科学生，课程材料将在网络上共享。 外联工作将与约翰霍普金斯为K-12学生提供的外联计划合作，将研究成果带给更广泛的受众，包括物理博览会，天文学和工程青年以及青年人才中心。将制作动画和网络模块，展示与赠款有关的概念。将与上述IGERT合作招收新生，IGERT正在与妇女学院和其他大学合作，这些大学的学生比例很高，来自代表性不足的群体。