CAREER: Investigating the Micromechanics of Fracture in Additively Manufactured Metals

该学院早期职业发展（CAREER）计划奖支持对金属材料增材制造的基础研究，旨在揭示对增材制造金属部件的加工-结构-断裂性能关系的基本理解。研究人员将使用新的实验和模拟，将加工与微观结构联系起来，以在使用中的零件所经历的一系列载荷条件下断裂性能。由此产生的知识将使结构部件的增材制造成为可能，这有可能减少材料浪费，重振美国制造业，并增加工程设计的灵活性。这项工作整合了研究，教育和推广，旨在利用公众对增材制造的兴趣作为一种工具，激发和教育大学预科生，本科生和研究生关于科学，技术，工程和数学的知识，重点是增加女性在这些领域的参与和保留。增材制造是一种具有无数潜在应用的技术，包括：制造定制组件（例如，在生物医学工业中），传统组件的替换和优化（例如，在国防部和能源部），并修复现有的组件。然而，在承载应用中采用增材制造组件需要了解这些组件的机械性能，即强度和断裂性能。增材制造组件的微观结构特征，即晶粒和内部孔隙度大小和方向，取决于组件内的局部热历史。这些异质和各向异性的微观结构特征将决定增材制造组件的断裂性能。然而，有一个缺乏基本知识的相对重要性，这些功能的断裂，特别是在多轴应力状态下。这项研究旨在揭示断裂的微观结构机制，即晶粒和孔径大小和形状如何在不锈钢合金中驱动韧性断裂过程，这些过程包括拉伸，剪切和组合载荷。通过表征内部微观结构特征和使用计算建模，这些微观结构特征对宏观多轴断裂行为的相对影响将被量化。将开发基于物理的断裂模型，以描述增材制造组件的应力状态相关统计断裂特性，作为微观结构特征的函数。

This Faculty Early Career Development (CAREER) Program award supports fundamental research on additive manufacturing of metallic materials, with the aim of uncovering a fundamental understanding of the processing-structure-fracture property relationships in metallic components made by additive manufacturing. The researchers will use novel experiments and simulations to link processing to microstructure to fracture properties over a range of loading conditions that would be experienced by parts in service. The resultant knowledge will enable the adoption of additive manufacturing for structural components, which has the potential to reduce waste of material, reinvigorate U.S. manufacturing, and increase design flexibility in engineering. This work integrates research, education, and outreach, and aims to use public interest in additive manufacturing as a vehicle by which to excite and educate pre-college, undergraduate, and graduate students about science, technology, engineering, and math, with a focus on increasing female participation and retention in these areas. Additive manufacturing is a technology has countless potential applications, including: fabrication of custom components (e.g., in the biomedical industry), replacement and optimization of legacy components (e.g., in the Departments of Defense and Energy), and repair of existing components. However, the adoption of additively manufactured components in load-bearing applications requires that the mechanical properties, namely the strength and fracture properties of these components, be understood.The microstructural characteristics of additively manufactured components, namely grain and internal porosity size and orientation, depend on the local thermal history within a component. These heterogeneous and anisotropic microstructural features will dictate the fracture performance of additively manufactured components. However, there is a lack of fundamental knowledge on the relative importance of these features on fracture, particularly under multiaxial stress states. This research aims to uncover the microstructural mechanisms of fracture, namely how grain and pore size and shape drive the ductile fracture process in a stainless steel alloy over a wide range of stress states that components would see in service, including tension, shear, and combined loading. Through characterization of internal microstructural features and the use of computational modeling, the relative effects of these microstructural features on the macroscopic multiaxial fracture behavior will be quantified. Physically-based fracture models will be developed to describe the stress-state dependent statistical fracture properties, as a function of microstructural features, of components made by additive manufacturing.