CAREER: Understanding Grain Level Residual Stresses Through Concurrent Modeling and Experiments

金属、合金和陶瓷等多晶材料在现代社会的基础设施中占据主导地位，无论是在原材料使用量方面还是在应用范围方面，都跨越了能源、交通、国防和其他部门。 在这些材料的加工过程中引入的应力，称为残余应力，在所有材料中普遍存在，并可能对性能产生巨大影响。 尽管它们的存在和关键作用的组件寿命，许多分析工作不能考虑残余应力。 该学院早期职业发展（CAREER）奖支持方法开发，以表征多晶材料中微米级的残余应力。这项研究将导致一个计算框架的发展，以占残余应力，并忠实地预测其分布。 该研究通过与阿贡国家实验室的高级光子源（APS）合作，利用了高能衍射显微镜的最新进展。该奖项还支持一个创新的教育计划，这是双重的。 首先，将开发一系列继续教育课程，重点是处理本研究中产生的残余应力分析，特别针对设计系统，结构分析和制造社区（即非材料）。 第二，将在普渡大学的太空日（一个现有的小学外展计划）中引入实践学习活动，重点是航空航天材料中的残余应力。为了建立对残余应力的基本理解，研究团队将：（i）开发建模框架以基于存在于各个滑移系统上的背应力公式来初始化和演化残余应力，（ii）通过高能X射线衍射显微镜测量多晶聚集体内晶粒和亚晶粒长度尺度上的残余应力及其发展，（iii）开发绘制结构合金块体内位错排列的技术，以及（iv）产生用于晶体塑性模型的验证数据集，所述晶体塑性模型包含先前不可能测量的状态相关变量。这项工作是基于最先进的实验和相同长度尺度的模拟之间的协同作用。 结果将明确阐明残余应力在多晶材料中跨长度尺度的作用，以开发更准确的合金寿命预测，并制造提供最小或有益残余应力的定制组件，因此更耐故障。

Polycrystalline materials such as metals, alloys and ceramics dominate the infrastructure of modern society in terms of both tons of raw material usage and in the breadth of applications, which span energy, transportation, defense, and other sectors. Stresses introduced during the processing of these materials, known as residual stresses, are ubiquitous in all materials and can have tremendous effects on performance. Despite their presence and critical role in component life, many analysis efforts cannot account for residual stresses. This Faculty Early Career Development (CAREER) award supports the method development to characterize residual stresses at the micron level within polycrystalline materials. The research will lead to the development of a computational framework to account for residual stresses, and faithfully predict their distributions. The research leverages recent advances in High Energy Diffraction Microscopy through collaboration with the Advanced Photon Source (APS) at Argonne National Laboratory. This award also supports an innovative educational program that is twofold. First, a series of continuing education courses will be developed focusing on the treatment of residual stress analyses produced in this research, specifically targeted towards the design systems, structural analysis, and manufacturing communities (i.e. non-materials) across professional societies. Second, hands-on learning activities will be introduced within Purdue's Space Day, an existing grade-school outreach program, which will focus on residual stresses in aerospace materials.In order to establish a basic understanding of residual stresses, the research team will: (i) develop a modeling framework to initialize and evolve residual stresses based on a backstress formulation present on individual slip systems, (ii) measure residual stresses and their development at the grain and sub-grain length scales within polycrystalline aggregates via high energy x-ray diffraction microscopy, (iii) develop techniques to map dislocation arrangements within the bulk of structural alloys, and (iv) produce validation datasets for crystal plasticity models containing state dependent variables that were previously impossible to measure. The work is predicated on a synergy between state-of-the-art experiments and simulations at the same length scale. The results will unequivocally elucidate the role of residual stresses across length scales in polycrystalline materials, in order to develop more accurate lifetime predictions of the alloys and fabricate tailored components that offer either minimal or beneficial residual stresses and therefore are more resistant to failures.