CAREER: Understanding the Combined Effect of Microstructure and Topology on the Mechanical Behavior of Additively Manufactured Lattice Structures

这项教师早期职业发展(Career)补助金由既定的激励竞争研究计划(EPSCoR)共同资助，专注于了解添加制造的格子结构(AML)的力学行为。AML是一种分层材料，其有效性质既取决于晶格结构的拓扑结构，也取决于母材的微观结构。因此，了解拓扑结构和微观结构之间的相互作用对于最大限度地发挥AMLS的潜在应用是必要的。一般来说，限制复杂工程系统性能的主要因素之一是传统的结构金属材料仅用于提供结构支撑。然而，AML设计的灵活性使其能够实现一系列多功能应用，如受控热传递、振动、能量管理和轻量化。在这项研究中，通过深入的实验和计算研究，微观结构和拓扑在控制各种加载条件下的力学行为的机械变形机制中的组合作用，将增强AMLS的潜力。这项资助的教育部分将提供：(1)高级设计团队有机会建立教育工具和技术，向视力有障碍的人传授机械工程概念；以及(2)为低收入学生提供实践研究机会。本项目的研究目标是了解微结构驱动机制(例如，由颗粒结构、取向和孔隙度引起的机制)和几何驱动事件(例如，单元-细胞屈曲、节点断裂和宏观剪切)对AML变形的具体贡献和相互作用，并确定在不同的加载条件下，哪些机制起主导作用。为了阐明局部微结构特征相对于拓扑属性的具体贡献，从微观结构和力学行为表征获得的实验数据将与由有限元(FE)模拟计算的局部应力状态相耦合。有限元分析将使用为AML定制的屈服准则，以捕捉由于层沉积期间重复的固相变化而产生的支柱的各向异性行为。新的屈服标准将建立在热处理控制的不同微观结构的压杆水平拉伸、压缩和剪切实验的基础上。这一奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) grant, co-funded by the Established Program to Stimulate Competitive Research (EPSCoR), focuses on understanding the mechanical behavior of additively manufactured lattice structures (AMLS). AMLS are hierarchical materials whose effective properties depend upon both the topology of the lattice structure and the base metallic material microstructure. Therefore, understanding the interplay between topology and microstructure is necessary to maximize the potential application of AMLS. In general, one of the major factors that limits a complex engineering system’s performance is that conventional structural metallic materials serve a singular purpose of providing structural support. However, flexibility in the design of AMLS enables an array of multifunctional applications, such as controlled heat transfer, vibration, energy management, and light-weighting. In this research, the potential of AMLS will be enhanced with an in-depth experimental-computational investigation of the combined role of microstructure and topology in the mechanical deformation mechanisms that control the mechanical behavior over a wide range of loading conditions. The educational part of this grant will provide: (1) an opportunity to senior design teams to build educational tools and techniques to teach mechanical engineering concepts to people with visual impairment; and (2) a hands-on research opportunity to low-income students.The research objectives of this project are understanding the specific contribution and interplay between the microstructurally driven mechanisms (e.g., those due to grain structures, orientation, and porosity) and geometrically driven events (e.g., unit-cell buckling, node fracturing, and macroscopic shear) on the deformation of AMLS, and determining which mechanisms dominate under different loading conditions. In order to elucidate the specific contribution of local microstructural features relative to topological attributes, experimental data obtained from microstructural and mechanical behavior characterization will be coupled with the local state of stress computed from finite element (FE) simulations. The FE analysis will use a yield criterion that will be customized for AMLS to capture the anisotropic behavior of the struts originating from the repeated solid-phase changes during layer deposition. The new yield criterion will be built based on the strut-level tension, compression, and shear experiments for different microstructures controlled by heat-treatment.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.