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）补助金由刺激竞争研究（EPSCoR）的建立计划共同资助，重点是了解增材制造晶格结构（AMLS）的力学行为。AMLS是一种分层材料，其有效性能既取决于晶格结构的拓扑结构，也取决于基体金属材料的微观结构。因此，了解拓扑结构和微观结构之间的相互作用对于最大化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结构金属材料的单一用途是提供结构支撑。然而，AMLS设计的灵活性使其能够实现一系列多功能应用，如受控传热、振动、能量管理和轻量化。在本研究中，AMLS的潜力将通过深入的实验计算研究来增强，研究微观结构和拓扑结构在大范围加载条件下控制力学行为的力学变形机制中的联合作用。此拨款的教育部分将提供：(1)让资深设计团队有机会建立教育工具和技术，向视障人士教授机械工程概念；(2)为低收入学生提供动手研究的机会。该项目的研究目标是了解微观结构驱动机制（如晶粒结构、取向和孔隙度）和几何驱动事件（如单元屈曲、节点破裂和宏观剪切）对AMLS变形的具体贡献和相互作用，并确定在不同加载条件下哪种机制占主导地位。为了阐明局部微观结构特征对拓扑属性的具体贡献，从微观结构和力学行为表征中获得的实验数据将与有限元模拟计算的局部应力状态相结合。有限元分析将使用为AMLS定制的屈服标准，以捕获层沉积过程中由重复固相变化引起的支板的各向异性行为。通过对不同热处理控制的微观结构进行杆级拉伸、压缩和剪切试验，建立新的屈服准则。该奖项反映了美国国家科学基金会的法定使命，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。

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.