Forward Model Based Strain Analysis in Highly Deformed Metallic Systems Using Electron Back-Scatter Diffraction Patterns

非技术总结在工程应用中使用金属和合金需要彻底了解这些材料在受到应力时会如何变形。尽管有时肉眼可以看到变形，但实际的变形过程发生在非常小的长度尺度上，这需要使用高放大倍数的电子显微镜。本研究将开发一种新的实验技术，以测量这些变形的高精度。这些详细的测量将有助于我们了解材料如何变形，最终，这将影响金属和合金如何在整个社会的结构应用中安全使用。本计划中开发的所有技术将通过出版物和开源代码的形式提供给社区。 公共信息中心还将探讨通过众包方式制作免费大学课本的可能性;这个“OpenChapters”项目将联合收割机由多个作者编写的单个章节组合成可定制的按需教科书，这些教科书将免费提供给大学生以及整个社会。相微观结构，这使得难以准确预测它们在施加应力的影响下将如何表现。 材料的变形行为的许多方面仍然知之甚少。从变形的多晶样品中提取晶格应变是一项艰巨的任务，由于新的探测器系统的可用性，特别是电子背散射衍射（EBSD），所提出的计划的选择工具，需要重新关注。PI和他的团队将采用基于物理的模型来预测EBSD模式，并将一种新的能力包括在模式生成算法中的变形张量。 结合最近开发的索引算法，将开发一种新的方法来确定变形张量组件匹配完整的模拟EBSD模式对他们的实验版本，与预期的应变分辨率优于0.0001在大样本区域。该计划有可能促进我们对现代工程材料以及较低对称性地质样品中微观和纳米尺度变形机制的理解。灵敏的EBSD探测器与改进的索引方案相结合，将为通过EBSD数据的全模式匹配来常规确定应变场奠定基础。这些算法将以同行评审的出版物和开源代码的形式提供给社区。在教育方面，OpenChapters项目将通过创建一个开源机制，通过众包方法生成免费教科书，以解决教科书成本迅速上升的问题。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYThe use of metals and alloys in engineering applications requires a thorough understanding of how these materials will behave when they are subjected to stresses that cause them to deform. Although the deformations can sometimes be visible to the naked eye, the actual deformation processes take place at very small length scales, which necessitates the use of electron microscopes operated at high magnification. This research will develop a new experimental technique to measure these deformations with high accuracy. Such detailed measurements will contribute to our understanding of how materials deform, and, ultimately, this will impact how metals and alloys can be used safely in structural applications throughout society. All techniques developed in this program will be made available to the community through publications and in the form of open source code. The PI will also explore the possibility of generating free college-level text books via a crowd-sourcing approach; this "OpenChapters" project will combine individual chapters written by multiple authors into customizable on-demand text books that will be freely available to college students as well as to society at large.TECHNICAL SUMMARYModern engineering materials often have a complex multi-phase microstructure that makes it difficult to accurately predict how they will behave under the influence of an applied stress. Many aspects of the deformation behavior of a material are still poorly understood. The extraction of lattice strains from deformed polycrystalline samples is a difficult undertaking that requires renewed attention due to the availability of new detector systems, in particular for electron back-scattered diffraction (EBSD), the tool of choice for the proposed program. The PI and his group will employ a physics-based model for the prediction of EBSD patterns and incorporate a new capability to include the deformation tensor in the pattern generation algorithm. In combination with a recently developed indexing algorithm, a new approach will be developed to determine the deformation tensor components by matching complete simulated EBSD patterns against their experimental versions, with an anticipated strain resolution of better than 0.0001 over large sample areas. This program has the potential to advance our understanding of micro- and nano-scale mechanisms of deformation in modern engineering materials as well as in lower symmetry geological samples. The combination of sensitive EBSD detectors with a modified indexing scheme will lay the foundation for the routine determination of strain fields by full-pattern matching of EBSD data. The algorithms will be made available to the community in peer-reviewed publications and as open source code. On the educational side, the OpenChapters project will address the rapidly rising cost of text books by creating an open source mechanism for the generation of free text books by a crowd-sourcing approach.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.