CAREER: Investigating the Micromechanics of Fracture in Additively Manufactured Metals

该学院早期职业发展(Career)计划奖支持金属材料添加剂制造的基础研究，旨在揭示通过添加剂制造的金属部件的加工-组织-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显微组织联系起来，以确定在一系列载荷条件下的断裂性能，这些载荷条件将使部件在使用中经历。由此产生的知识将使结构部件采用附加制造成为可能，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，旨在利用公众对添加剂制造的兴趣作为一种媒介，通过它来激发和教育大学预科、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度和留存率。添加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，在生物医学行业)、替换和优化遗留组件(例如，在国防部和能源部)以及修复现有组件。然而，在承载应用中采用添加制造的部件需要了解这些部件的力学性能，即这些部件的强度和断裂性能。添加制造的部件的微观结构特征，即颗粒和内部气孔的大小和取向，取决于部件内的局部热历史。这些不均匀和各向异性的微观结构特征将决定添加制造的部件的断裂性能。然而，对于这些特征对骨折的相对重要性，特别是在多轴应力状态下，缺乏基本的知识。这项研究旨在揭示断裂的微观组织机制，即晶粒和孔的大小和形状如何驱动不锈钢合金在各种应力状态下的延性断裂过程，这些应力状态包括拉伸、剪切和联合加载。通过内部微观结构特征的表征和计算模型的使用，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。基于物理的断裂模型将被开发来描述作为微观结构特征的函数的应力状态相关的统计断裂特性，这些特性是通过添加制造制造的部件的。

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.