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Predictive microstructural modeling of grain-boundary interactions and their effects on overall crystalline behavior.

机译：晶界相互作用的预测性微结构建模及其对整体晶体行为的影响。

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摘要

A dislocation-density grain boundary interaction scheme (DDGBI) has been developed to account for complex interrelated dislocation-density interactions of emission, absorption and transmission in grain-boundary (GB) regions for bicrystals and polycrystals with different random and coincident site lattice (CSL) GB arrangements. This scheme is coupled to a dislocation-density crystalline plasticity formulation and specialized finite-element scheme at different physical scales. The DDGBI scheme is based on slip-system compatibility, local resolved shear stresses, and immobile and mobile dislocation-density activities at GBs. A conservation law for dislocation-densities is used to balance dislocation-density absorption, transmission and emission in GB regions. It is shown that dislocation-density absorptions and pile-ups will increase immobile dislocation-densities in high angle CSL boundaries, such as Sigma17b. Lower angle CSLs, such as Sigma1, are characterized by high transmission rates and insignificant GB dislocation-density accumulations. The identification of how different material mechanisms dominate underscores that GB activities, such as dislocation-density absorption, transmission and emission are interrelated interactions. These GB processes can be potentially controlled for desired material behavior. This methodology, together with grain boundary sliding (GBS) scheme and a misorientation dependence on initial GB dislocation-densities, was extended to account for grain size effects on strength. The behavior of polycrystalline aggregates with random low angle and random high angle GBs was also investigated with different crack lengths. For aggregates with random low angle GBs, dislocation-density transmission dominates at the GBs, which indicates that the low angle GB will not significantly change crack growth orientations. For aggregates with random high angle GBs, extensive dislocation-density absorption and pile-ups occur. The high stresses along the GB regions can result in intergranular crack growth due to potential crack nucleation sites in the GB. It is also shown that GB sliding affects crack behavior by attenuating normal stresses and dislocation-density accumulation at critical GB interfaces.
机译：已经开发了位错-密度晶界相互作用方案（DDGBI），以解决具有不同随机和重合位点晶格（CSL）的双晶和多晶在晶界（GB）区域中发射，吸收和透射的复杂相关位错-密度相互作用。 ）国标安排。该方案与位错密度晶体可塑性公式和专门的有限元方案在不同的物理规模上耦合。 DDGBI方案基于滑移系统兼容性，局部解析切应力以及GBs的不动和移动位错密度活动。使用位错密度守恒定律来平衡GB区域中的位错密度吸收，传输和发射。结果表明，位错密度吸收和堆积会增加大角度CSL边界（例如Sigma17b）中的不动位错密度。较低角度的CSL（例如Sigma1）的特征是高传输速率和微不足道的GB位错密度累积。对不同物质机制如何起主导作用的识别强调了GB活动（例如位错密度吸收，传输和发射）是相互关联的相互作用。可以针对所需的材料行为来控制这些GB过程。这种方法，连同晶界滑动（GBS）方案和取向错误对初始GB位错密度的依赖关系，被扩展到考虑晶粒尺寸对强度的影响。还研究了不同裂纹长度下具有随机低角度和随机高角度GBs的多晶聚集体的行为。对于具有随机低角度GBs的骨料，位错密度传递在GBs上占主导地位，这表明低角度GB不会显着改变裂纹扩展方向。对于具有随机大角度GB的骨料，会发生大量的位错密度吸收和堆积。由于GB中潜在的裂纹成核位置，沿GB区域的高应力可能导致晶间裂纹扩展。研究还表明，GB滑动会通过削弱GB临界界面处的正应力和位错密度累积而影响裂纹行为。

著录项

  • 作者

    Shi, Jibin.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Engineering Mechanical.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 154 p.
  • 总页数 154
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;工程材料学;
  • 关键词

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