CAREER: Bridging Experiments and Multiscale Modeling of Size- and Temperature-dependent Phenomena in Polycrystalline Plasticity

这项教师早期职业发展计划(CALE)提出了一种新的多尺度建模和模拟方法，结合实验，在小尺寸晶体固体中缺陷介导的变形和断裂的基础研究中。其目的是研究材料长度尺度(例如，晶粒度)和结构长度尺度(例如，器件尺寸)对温度相关的断裂转变和蠕变的综合影响。脆性和蠕变是小型器件和纳米结构金属材料的重要可靠性问题。模拟的核心是基于缺陷动力学的中尺度框架，它将提供：(I)依赖于尺度和温度的机械响应；以及(Ii)用于断裂转变的连续模型的微裂纹形核标准。这个中尺度框架将作为原子尺度传递的信息中的连字符，按需调用分子动力学模拟，以进行定向的位错-界面相互作用，一直到连续尺度，在连续尺度上，模型预测可以用实验来验证。小规模设备的社会好处来自于它们在新兴技术中的普及，这些技术正在影响我们的工作、交流、学习、治疗疾病的方式，甚至是娱乐的方式。拟议的活动将有助于提高我们对纳米和微米尺度塑性的理解，这将直接应用于小型设备中的结构部件。塑性多尺度建模对于减少新器件和新材料的开发成本和制造时间以及评估其可靠性和机械完整性将起到关键作用。通过开发材料纳米力学研究生课程、本科生参与研究、与北非大学的国际交流计划以及在外联活动中使用可视化来帮助不同背景和学习路径的学生保持对晶体缺陷的物理直观理解，实现了研究和教育的一体化。

This Faculty Early Career Development Plan (CAREER) proposes a new multiscale modeling and simulation methodology, integrated with experiments, in fundamental studies of defect-mediated deformation and fracture in crystalline solids at small length scales. The objectives are to investigate the combined effects of material length scales (e.g. grain size) and structural length scales (e.g. device dimensions) on temperature-dependent fracture transitions and creep. Brittleness and creep are important reliability issues in small-scale devices and nanostructured metallic materials. Central to modeling is a mesoscale framework based on the dynamics of defects, which will deliver: (i) scale- and temperature-dependent mechanical response; and (ii) microcrack nucleation criteria for use in continuum modeling of fracture transitions. This mesoscale framework will serve as the hyphen in information passing from the atomic scale, with on-demand calls to molecular dynamics simulations for targeted dislocation-interface interactions, all theway to the continuum scale, where model predictions can be validated with experiments.Societal benefits of small-scale devices, such as micro/nano-electro-mechanical systems and electronic devices, stem from their pervasiveness in the emerging technologies that are affecting the ways in which we work, communicate, learn, treat diseases, and are even entertained. The proposed activities will help improve our understanding of plasticity at nano- and micro-scales, which has direct applications to structural components in small-scale devices. Multiscale modeling of plasticity will play a key role to reduce development costs and manufacturing times of new devices and materials and to assess their reliability and mechanical integrity. Integration of research and education is achieved through the development of a materials nanomechanics graduate course, involvement of undergraduates in research, an international exchange program with universities in North-Africa and use of visualization in outreach activities to help students with different backgrounds and learning paths retain a physically intuitive comprehension of crystal defects.