Deformation, Strength, Fatigue and Fracture of Gradient Nanostructured Metals

非技术摘要：金属在我们社会的基础设施和整体经济发展中发挥着至关重要的作用，这反映在金属的年度全球市场价值接近一万亿美元的事实上。在过去的五年中，一种称为梯度纳米结构金属的新型纳米材料已经作为一种材料类别出现，其表现出抗拉强度、良好的拉伸延展性、增强的应变硬化、上级断裂韧性和抗疲劳性的不寻常的组合。然而，目前对控制这些材料性能的基本机制缺乏了解，严重限制了我们为特定应用定制或优化其性能的能力。另一方面，计算建模和仿真能力的最新进展提供了前所未有的机会，以推进我们在微米和纳米尺度上对材料力学性能的理解的知识前沿。拟议的研究将利用尖端的多尺度建模和仿真方法来解决有关梯度纳米结构金属的机械性能和行为的基本问题。该项目将在最先进的计算技术方面培训研究生和本科生。技术摘要拟议的研究将解决以下问题：什么是控制梯度纳米结构金属的机械性能的变形机制？如何设计梯度微纳米结构以优化梯度纳米结构金属的力学响应？研究中的问题将通过一个多尺度的建模方法，结合有限元方法，应变梯度塑性，内聚建模，晶体塑性，位错动力学和分子动力学模拟将被用来研究梯度纳米结构金属的变形和破坏机制。技术方法将基于PI开发的经验和理论/模拟能力。该工作将通过超大规模和高分辨率的原子动力学和位错动力学模拟阐明控制变形的机制，通过连续应变梯度塑性和疲劳和断裂行为的内聚模型解释实验数据和现象，并指导结构优化和加工的进一步研究。拟议工作中的超大规模模拟将在国家计算科学研究所进行，其余的拟议计算工作将在布朗大学计算和可视化中心进行。该项目将在最先进的计算技术方面培训研究生和本科生。

Non-technical Abstract:Metals play essential roles in infrastructural and overall economic developments of our society, as reflected by the fact that the annual global market value of metals is close to a trillion US dollars. During the last five years, a new class of nano materials called gradient nanostructured metals have emerged as a material class which exhibits an unusual combination of ultrahigh strength, good tensile ductility, enhanced strain hardening, superior fracture toughness and fatigue resistance. However, the current lack of understanding of the underlying mechanisms that control the properties of these materials severely limits our ability to tailor or optimize their properties for specific applications. On the other hand, recent advances in computational modeling and simulation capabilities are providing unprecedented opportunities to advance the knowledge frontier in our understanding of mechanical properties of materials at micro- and nano-scales. The proposed research will take advantage of the cutting-edge multiscale modeling and simulation methods to address the fundamental issues with regard to the mechanical properties and behavior of gradient nanostructured metals. The project will train graduate and undergraduate students in state of the art computational techniques. Technical AbstractThe proposed research will address the following questions: What are the deformation mechanisms that control the mechanical properties of gradient nanostructured metals? How to design the gradient micro- and nanostructures to optimize the mechanical responses of gradient nanostructured metals? The problems under study will be tackled via a multiscale modeling approach that combines finite element method, strain gradient plasticity, cohesive modeling, crystal plasticity, dislocation dynamics and molecular dynamics simulations will be used to investigate the deformation and failure mechanisms of gradient nanostructured metals. The technical approach will be based on the experience and theoretical/simulation capabilities developed by the PI. The proposed work will clarify the controlling deformation mechanisms through ultra-large-scale and high-resolution atomistic and dislocation dynamics simulations, interpret the experimental data and phenomena through continuum strain gradient plasticity and cohesive modeling of fatigue and fracture behavior, and guide further research in structural optimization and processing. The ultra-large scale simulations in the proposed work will be performed on the National Institute for Computational Sciences, and the rest of the proposed computational work will be performed at the Center for Computing and Visualization at Brown University. The project will train graduate and undergraduate students in state of the art computational techniques.