Relationship Between Atomic Structure and Mechanical Properties of Interfaces and Free Surfaces

原子结构与界面和自由表面力学性能之间的关系

• 批准号: 9112196
• 负责人: John Bassani
• 金额: --
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-07-15 至 1995-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9112196&HistoricalAwards=false
• 关键词: Relationship; Between; Atomic; Structure; Mechanical

Research will be conducted on the mechanical properties of grain boundaries and bicrystals from both atomistic and continuum points of view. The validity of a continuum description of the heterogeneous nature of grain boundaries at the atomic scale has been established through comparisons with detailed atomistic simulations. This has led to the classification of locally stable, metastable and unstable grain boundary structures and identification of the physically more reasonable structure among the multiple ones found for a given bicrystal. The research builds on these findings and continues to emphasize the relation between atomistic and continuum theories. A detailed study of the internal stresses in interface regions and at free surfaces, which can generally be of significant magnitude, will be undertaken. The implication of the loss of positive definitieness or strong ellipticity for the fourth-order tensor of elastic moduli and the corresponding possibiity, respectively, of locally negative strain energies or bifurcations and discontinuities will be studied. Better bounds or estimates for the effective properties of the atomically heterogeneous continuum model will be developed. The theory wil be applied to grain boundaries and interfaces between two different metals, free surfaces, interfaces between thin films and substrates, and the influence of alloying, manifested in segregation and/or ordering, on elastic properties. %%% Studies of the mechanical properties of materials usually use a continuum approach even though materials are known to be made up of discrete elements such as atoms and molecules. The mechanical properties are dependent on the structure of grain boundaries bewteen crystal grains and on the existence of bicrystals. It is possible to study the structure of grain boundaries from an atomistic approach. However, there is very little work which connects the atomistic study of grain boundaries with the continuum approach. This grant proposes to do just this. A consistent approach will be taken to study grain boundaries from an atomistic point of view and then connect this with the continuum description.

将对粮食的力学性能进行研究 边界和双晶体从原子和连续点 的观点。 连续描述的有效性 原子尺度上晶界的异质性 通过与详细的原子理论进行比较， 模拟 这导致了局部稳定的分类， 亚稳态和不稳定的晶界结构， 确定物理上更合理的结构， 对于给定的双晶体发现的多个。 这项研究建立 并继续强调这些发现之间的关系， 原子论和连续统理论。 详细研究内部 界面区域和自由表面的应力， 一般来说，将有很大的规模。 的 失去肯定性或强 四阶弹性模量张量的椭圆性和 局部负应变的相应可能性 将研究能量或分叉和不连续性。 的有效性质的更好的界或估计， 原子不均匀连续体模型将被开发。 的 理论将应用于晶界和界面之间 两种不同的金属，自由表面，薄膜之间的界面 以及合金化的影响，表现在 偏析和/或有序化对弹性性能的影响。 %%% 研究材料的机械性能通常使用 连续体方法，即使已知材料由 原子和分子等离散元素。 机械 性能取决于晶界的结构 晶粒间的相互作用和双晶的存在。 是 可以研究晶界的结构， 原子论方法 然而，很少有工作， 将晶界的原子学研究与连续体 approach. 这笔赠款正是为了做到这一点。 一致的 将采取的方法来研究晶界从原子 然后将其与连续统描述联系起来。