Microstructure: Dislocations, Creases, and Grains

微观结构：位错、折痕和晶粒

• 批准号: 9805422
• 负责人: James Sethna
• 金额: $ 20.7万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-15 至 2001-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9805422&HistoricalAwards=false
• 关键词: Microstructure; Dislocations; Creases; Grains

9805422SethnaThis award supports research in the area of microstructure of materials that results from expulsion of external strain into sharp boundaries. This occurs at grain boundaries in crystals, at focal conic defects in smectic liquid crystals, at vortex lines in superconductors, and at creases in crumbled paper. The PI will focus on specific projects in three areas: frustrated crystals, nonlinearities and dispersion, and paper crumbling. The first focuses on new phases. Dislocation lines can relieve external strain, but can also form in response to frustration in the crystal structure. The PI will introduce a term in the free energy of anisotropic, chiral crystals and aim to predict and characterize the resulting defect-lattice phases. In the second area, the PI will study the perturbative effects of nonlinearity and disperson on the continuum interactions between microcracks and observe a hitherto ignored term in the continuum energy. This study is important to realistic simulation of interacting dislocation lines where connection between interactions at atomic scales to continuum elastic theory is required. The final area is concerned with the large scale dynamics of microstructure. The PI will study a model motivated by the acoustic emission found during martensitic transformations and during the crumbling of paper. %%%This talented PI will perform theoretical research aimed at a better understanding of the nature and formation of small scale structure that forms in association with defects in materials. The research will also focus on the dynamics of this microstructure that is relevant to how paper crumbles and a class of structural transformations. The proposed research also bears on how to include important information about materials at the atomic level to describe correctly dynamical phenomena at intermediate and macroscopic length scales. ***

9805422Sethna该奖项支持材料微观结构领域的研究，该领域的研究是由外部应变驱逐到尖锐边界引起的。 这种现象发生在晶体的晶界、近晶液晶的焦锥缺陷、超导体的涡旋线和碎纸的折痕处。 PI将专注于三个领域的具体项目：受挫折的晶体，非线性和色散，以及纸张破碎。 第一个重点是新阶段。位错线可以缓解外部应变，但也可以响应于晶体结构中的挫折而形成。 PI将在各向异性手性晶体的自由能中引入一个术语，旨在预测和表征所产生的缺陷晶格相。 在第二个领域，PI将研究微裂纹之间的连续相互作用的非线性和disperson的扰动效应，并观察到一个迄今为止被忽视的项在连续能量。 这项研究是重要的现实模拟的相互作用位错线之间的相互作用在原子尺度上的连续弹性理论的连接是必需的。最后一个领域涉及微观结构的大尺度动力学。 PI将研究一个由马氏体相变和纸张破碎过程中发现的声发射激发的模型。这位才华横溢的PI将进行理论研究，旨在更好地理解与材料缺陷相关的小尺度结构的性质和形成。 该研究还将重点关注这种微观结构的动力学，这与纸张如何破碎和一类结构转变有关。 拟议的研究还涉及如何在原子水平上包含有关材料的重要信息，以正确描述中等和宏观长度尺度的动力学现象。 ***