Methods for Atomistic Input into Initial Yield and Plastic Flow Criteria for Nanocrystalline Materials

纳米晶材料初始屈服强度和塑性流动准则的原子输入方法

• 批准号: 1030103
• 负责人: David McDowell
• 金额: $ 27.58万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1030103&HistoricalAwards=false
• 关键词: Methods; Atomistic; Input; into; Initial

The objective of this research is to employ molecular dynamics simulations to shed light on the proper forms for the constitutive description of stress-state dependent inelastic deformation modes for some nanocrystalline metals, including grain boundary shuffling/sliding, grain boundary dislocation nucleation, absorption and desorption, and free volume exchange of grain boundaries with triple junctions. The research approach will emphasize methods to simulate and quantitatively characterize distinct contributions of competing deformation mechanisms of grain boundary sliding, grain boundary dislocation nucleation, absorption and desorption, and grain core dislocation activity in three-dimensional nanocrystalline ensembles. To accomplish the above goals, the research integrates concepts and methods that bridge between materials science/physics and the engineering sciences, in particular mechanics of materials.The broader outcomes of this project will be used to gain fundamental new understanding of behavior of nanocrystalline materials, which can be used to inform improved continuum models of nanocrystalline materials with competing modes of deformation; to motivate proper, atomistically-consistent forms of yield surfaces in which to embed continuum models, including tension-compression asymmetry and general stress state effects; and to estimate the spectra of activation energy and volumes for both bulk- and grain boundary-mediated inelastic deformation modes, useful for modeling kinetics at long time scales. The research will provide advanced training for both graduate and undergraduate students. Moreover, outreach activities will be conducted to motivate high-school students to pursue careers in engineering research and education.

本研究的目的是利用分子动力学模拟来揭示某些纳米晶金属与应力状态相关的非弹性变形模式的本构描述的正确形式，包括晶界改组/滑动、晶界位错成核、吸收和解吸以及三结晶界的自由体积交换。该研究方法将强调模拟和定量表征三维纳米晶系综中晶界滑动、晶界位错成核、吸收和解吸以及晶核位错活动的竞争变形机制的独特贡献的方法。为了实现上述目标，该研究整合了材料科学/物理学和工程科学（特别是材料力学）之间桥梁的概念和方法。该项目的更广泛成果将用于获得对纳米晶材料行为的基本新理解，这可用于为具有竞争变形模式的纳米晶材料的改进连续体模型提供信息；激发适当的、原子一致的屈服面形式，在其中嵌入连续模型，包括拉压不对称和一般应力状态效应；并估计体相和晶界介导的非弹性变形模式的活化能和体积谱，这对于长时间尺度的动力学建模很有用。该研究将为研究生和本科生提供高级培训。此外，还将开展外展活动，以激励高中生从事工程研究和教育事业。