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.

透明的多晶轻质重量陶瓷提供了处理性，光学特性和机械性能的独特组合，使其适用于透明装甲，航空的光学和高压玻璃的应用。不幸的是，这些材料通常比其他眼镜表现出更大的强度差异，从而使它们不适合这种高可靠性应用。这种与工业联络的赠款机会（Goali）项目是基于以下假设：在材料晶体之间的边界上的化学变化对整体机械行为的影响很大。了解哪种化学在这些边界上有利，可以改善材料的工程，并为应用作为高强度光学元素创建新市场。实现这一目标将发展实验机制；促进民族健康，繁荣和福利；并确保国防。为了建立这一假设，必须对大小的样品进行机械测试和仿真，从人毛的宽度的1/100范围（以测量单晶边界）到整个成分的大小。 新开发的测试方法直到最近才使这种实验可行，从而创造了新的机会来理解这一问题。作为该项目的一部分，将在工业伙伴提供学生实习，在研究小组中将招募代表性的本科生，并且将通过学习女孩学习材料营的活动来激励潜在的女学生。大型MGAL2O4尖晶石的机械强度相当多可变可变异性，从而在局部变异中被假设是从域中变异和化学构成的，并且是从晶界变异的。 但是，颗粒状的几何形状，晶界各向异性以及晶界化学的变化使相关的简单指标，例如平均边界组成和平均强度挑战。为了发展对尖晶石机械行为的机制的理解，这项工作桥梁实验相关的长度尺度：从测量单个边界的断裂特性和晶界化学，到预测大型标本及其性质分布的断裂强度。该项目开发了数字粒子跟踪方法，用于在透射电子显微镜中进行原位进行的单晶边界断裂实验中映射不断发展的应变。由相关的有限元分析开发的凝聚区模型可以与测量的晶界化学和不良方向相关。可以在中尺度（数十个晶粒）上观察到晶界和大量性质分布随各向异性的函数。这使我们能够定义代表性元素，以用于宏观样本的连续分析。 在此规模上，将使用实验合理合理的组成梯度，残余应力梯度和晶界特性分布来预测宏观强度的分布。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力优点和更广泛影响的评估标准来通过评估来进行评估的。

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.