GOALI: Understanding Light-weight Transparent Ceramic Mechanical Response: From Single Grain Boundary to Bulk Material

GOALI：了解轻质透明陶瓷机械响应：从单晶界到散装材料

• 批准号: 1825466
• 负责人: John Lambros
• 金额: $ 47.73万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1825466&HistoricalAwards=false
• 关键词: GOALI; Understanding; Light; weight; Transparent

Transparent polycrystalline light-weight ceramics provide a unique combination of processibility, optical properties, and mechanical properties making them suitable for applications as transparent armor, optics for aviation, and high-pressure glass for submarines. Unfortunately, these materials often exhibit greater variations in strength than other glasses, making them less suitable for such high-reliability applications. This Grant Opportunities for Academic Liaison with Industry (GOALI) project is based on the hypothesis that minor changes in chemistry at the boundaries between material crystals have a large effect on the overall mechanical behavior. Understanding what chemistry is favorable at these boundaries could allow for improved engineering of the material and create new markets for applications as a high strength optical element. Achieving this goal will progress experimental mechanics; advance the national health, prosperity, and welfare; and secure the national defense. To establish this hypothesis, mechanical testing and simulation must be performed on samples ranging in size from 1/100th of the width of a human hair (to measure single crystal boundaries) to the size of the entire component. Newly developed testing methods have only recently made such experiments feasible, thus creating new opportunities to understand this problem. As part of the project, student internships will be provided at the industrial partner, underrepresented undergraduate students will be recruited in the research group, and prospective female students will be motivated through Girls Learning about Materials Camp activity.The mechanical strength of large-format MgAl2O4 spinel exhibits considerable variability that is hypothesized to result from local variations in grain boundary stoichiometry and chemistry. However, the granular geometry, grain boundary anisotropy, and variations in grain boundary chemistry make relating simple metrics like average boundary composition and average strength challenging. To develop a mechanism-informed understanding of the mechanical behavior of spinel, this work bridges experimentally relevant length scales: from measuring fracture properties and grain boundary chemistry on single boundaries to predicting the fracture strength of large specimens and their property distributions. The project develops digital particle-tracking methods for mapping evolving strain during single grain boundary fracture experiments performed in situ in a transmission electron microscope. Cohesive zone models developed from associated finite element analyses can be correlated with measured grain boundary chemistries and misorientations. Grain boundary and bulk property distributions as a function of anisotropy can be observed at the mesoscale (dozens of grains). This allows us to define representative volume elements for use in a continuum analysis of the macroscopic samples. At this scale, experimentally reasonable compositional gradients, residual stress gradients, and grain boundary property distributions will be used to predict the distribution of macroscopic strength.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

透明多晶轻质陶瓷提供了可加工性、光学性能和机械性能的独特组合，使其适用于透明装甲、航空光学器件和潜艇高压玻璃等应用。不幸的是，这些材料通常比其他玻璃表现出更大的强度变化，使得它们不太适合这种高可靠性应用。该学术与工业联络资助机会 (GOALI) 项目基于这样的假设：材料晶体之间边界化学的微小变化会对整体机械行为产生很大影响。了解在这些边界上哪些化学物质是有利的，可以改进材料的工程设计，并为高强度光学元件的应用创造新的市场。实现这一目标将推动实验力学的进步；促进国民健康、繁荣和福利；并确保国防安全。为了建立这一假设，必须对尺寸从人类头发宽度的 1/100（用于测量单晶边界）到整个组件尺寸的样品进行机械测试和模拟。 新开发的测试方法最近才使此类实验变得可行，从而为理解这个问题创造了新的机会。作为该项目的一部分，将在工业合作伙伴处提供学生实习机会，研究小组将招募代表性不足的本科生，并通过女孩学习材料营活动来激励未来的女学生。大型 MgAl2O4 的机械强度尖晶石表现出相当大的变异性，推测这是由于晶界化学计量和化学的局部变化造成的。 然而，颗粒几何形状、晶界各向异性和晶界化学变化使得平均晶界成分和平均强度等简单指标的关联变得具有挑战性。为了从机制上理解尖晶石的机械行为，这项工作在实验上连接了相关的长度尺度：从测量单晶界上的断裂特性和晶界化学到预测大型样品的断裂强度及其特性分布。该项目开发了数字粒子跟踪方法，用于绘制透射电子显微镜原位进行的单晶界断裂实验过程中不断变化的应变。根据相关有限元分析开发的内聚区模型可以与测量的晶界化学成分和取向差相关联。可以在介观尺度（数十个晶粒）观察到作为各向异性函数的晶界和整体属性分布。这使我们能够定义用于宏观样品连续分析的代表性体积元素。 在这个尺度上，实验上合理的成分梯度、残余应力梯度和晶界属性分布将用于预测宏观强度的分布。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优势和能力进行评估，被认为值得支持。更广泛的影响审查标准。

项目成果

Measuring representative volume elements from high‐resolution grain‐scale strain fields

测量高分辨率颗粒尺度应变场中的代表性体积元素

• DOI: 10.1111/str.12423
• 发表时间: 2022
• 期刊: Strain
• 影响因子: 2.1
• 作者: B. Vieira, Renato;Lambros, John
• 通讯作者: Lambros, John

Full-field deformation measurements in the transmission electron microscope using digital image correlation and particle tracking

使用数字图像相关和粒子跟踪在透射电子显微镜中进行全场变形测量

• DOI: 10.1016/j.matchar.2021.111598
• 发表时间: 2022
• 期刊: Materials Characterization
• 影响因子: 4.7
• 作者: Zhang, Y.;Feng, L.;Dillon, S.;Lambros, J.
• 通讯作者: Lambros, J.

Representative volume elements for plasticity and creep measured from high-resolution microscale strain fields

从高分辨率微尺度应变场测量的塑性和蠕变的代表性体积元素

• DOI: 10.1016/j.actamat.2021.117021
• 发表时间: 2021
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: Vieira, R.B.;Sehitoglu, H.;Lambros, J.
• 通讯作者: Lambros, J.