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.

技术摘要这一奖项支持理论和计算研究以及有关无序固体变形和断裂的理论研究和教育，以确定宏观机械响应的微观机制。一个重点将是无定形聚合物的故障模式。在这里，链连通性导致异常变形模式，包括狂热形成，颈部和明显的应变硬化。第二个重点是在稳定，绝对剪切或无序固体压缩过程中的一般缩放行为。塑性变形和断裂的传统工程模型基于具有空间平均响应的现象学本质关系的宏观连续性方程。实验提供了有关此响应的显微镜起源的有限信息。 PI将进行模拟，以提供有关宏观力学与分子尺度相互作用和变形机制之间联系的新见解。聚合物分子的连通性导致拓扑纠缠。无定形聚合物的机械性能的大多数模型都认为这些纠缠像化学交联一样。在变形过程中跟踪纠缠的运动将提供这些模型和新信息的详细测试，以作为改善它们的基础。聚合物结构和分子摩擦对纠缠，应力 - 应变关系和失败方式的影响。在聚合物界面上进行纠缠的研究将提供对聚合物之间的聚合物焊缝和摩擦力的微观理解。剪切系统的研究在发展对非平衡行为的新理解中发挥了重要作用。模拟将探索无序系统的绝对剪切或压缩的缩放行为。系统通过一系列的地震来发展，例如具有大小的功率定律分布的事件。将研究各个事件的缩放和时空动力学，将它们核定的条件以及它们在长时间和距离内的相关性。具体的问题将是惯性和不可逆转的损害如何影响非平衡关键现象。该项目将通过培训各种跨学科建模和计算方法的学生为二十一世纪的劳动力做出贡献。这项培训将超越赠款支持的学生对与“建模复杂系统”的本地IGERT相关的学生。关于多尺度建模的新课程将与IGERT协调。该课程将针对来自一系列学科的科学和工程专业学生，课程材料将在网络上共享。 外展工作将与针对K-12学生的约翰·霍普金斯（John Hopkins）的外展计划（包括物理博览会，天文学和工程青年以及才华横溢的青年中心）合作，将研究成果带给更广泛的受众群体。将开发用于展示与赠款相关的概念的动画和基于Web的模块。招募新学生将与上述IGERT合作完成，该iGert与女子大学和其他大学合作，来自代表性不足的群体中的学生比例很高。《综合技术简介》颁发奖项支持理论和计算研究和教育，以更好地理解材料对应用压力的材料如何变形。该研究将重点放在彼此纠缠的长链样分子制成的材料上。 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的反应。该研究应阐明链条的纠结以及纠缠以精确的数学意义变化的方式。这项研究涉及影响许多技术的基本过程。一个推力将检查变形和断裂的一般方面，这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败有关。另一个将探索无定形聚合物中的专业行为，从而影响其作为粘合剂，结构材料和固体润滑剂的功能。对上述系统的深入了解将有助于设计和建模结构组件，并开发具有改进特性的量身定制材料。研究项目还将成为新的计算建模技术的测试基础，这些技术伴随着材料的描述截然不同。这些方法有可能改善广泛的复杂材料行为的建模，而不是本项目中涉及的特定项目。该项目将通过培训各种跨学科建模和计算方法的学生为二十世纪的劳动力做出贡献。这项培训将超越赠款支持的学生对与“建模复杂系统”的本地IGERT相关的学生。关于多尺度建模的新课程将与IGERT协调。该课程将针对来自一系列学科的科学和工程专业学生，课程材料将在网络上共享。 外展工作将与针对K-12学生的约翰·霍普金斯（John Hopkins）的外展计划（包括物理博览会，天文学和工程青年以及才华横溢的青年中心）合作，将研究成果带给更广泛的受众群体。将开发用于展示与赠款相关的概念的动画和基于Web的模块。将与上述IGERT合作进行新生的招聘，该公司与女子大学和其他大学合作，来自代表性不足的群体的学生比例很高。