CAREER: Unveiling the Governing Mechanisms of Fatigue Failure in Additively Manufactured Aluminum

增材制造（AM），通常被称为3D打印，是一种令人兴奋的技术，与传统制造相比，它可以在复杂金属零件的生产中提供更大的灵活性和效率。然而，在结构部件必须承受载荷的应用中（在某些情况下，部件必须长时间承受重复载荷），AM作为一种可行且安全的替代方案的路径处于关键节点。这种变革性制造技术的广泛采用受到以下事实的阻碍：目前无法预测增材制造的金属部件何时以及为什么会失效，并且无法相应地设计部件以降低失效风险。这对许多希望使用AM生产金属承重部件的行业来说是一个主要问题。该学院早期职业发展计划（CAREER）奖支持基础研究，以解决这一迫切需求，并使金属增材制造在许多行业，包括航空航天，汽车，生物医学，制造业和国防中的扩展，但安全使用。该研究与一个独特的外展计划紧密结合，该计划将吸引不同年龄段和背景的学生，包括来自犹他州农村地区的中学生。这项CAREER奖支持的研究是通过发现增材制造铝中的3D，微观结构敏感，疲劳裂纹驱动机制，将AM的使用扩展到疲劳关键应用的基本步骤。将开展两项平行的研究重点。一个推力将集中在实验表征的微观结构特征的3D邻域中观察到的疲劳裂纹的铝试样由激光粉末床融合。第二个推力将集中在数值表征的局部微观力学领域，在3D中演变为底层的，制造引起的微观结构和缺陷分布的函数，特别关注残余应力不相容性，孔隙度和表面粗糙度。数据驱动的方法将被利用在整个实验和数值数据集，提供新的见解的机制，负责试样之间的疲劳失效。虽然研究的重点是铝合金，但预计有关几何缺陷（如孔隙和表面粗糙度）的相对重要性的研究结果，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

Additive manufacturing (AM), often referred to as 3D printing, is an exciting technology that can offer more flexibility and efficiency in the production of complex metal parts compared to conventional manufacturing. However, the path to AM as a viable and safe alternative in applications where structural components must carry loads (in some cases, where components must sustain repetitive loading over long periods of time) is at a critical junction. The widespread incorporation of this transformative manufacturing technology is hampered by the fact that it is currently not possible to predict when and why an additively manufactured metal component might fail, and to design the component accordingly to mitigate risk of failure. This presents a major problem for many industries that are looking to use AM to produce metal load-bearing components. This Faculty Early Career Development Program (CAREER) award supports fundamental research to address this pressing need and to enable the expanded, yet safe, use of metal AM in many industries, including aerospace, automotive, biomedical, manufacturing, and national defense. The research is closely integrated with a unique outreach program that will engage students across different age levels and backgrounds, including middle-school students from rural locations in Utah.The research supported by this CAREER award is a fundamental step toward expanding the use of AM to fatigue-critical applications through the discovery of 3D, microstructure-sensitive, fatigue-crack driving mechanisms in additively manufactured aluminum. Two parallel research thrusts will be carried out. One thrust will focus on experimentally characterizing the microstructural features in 3D neighborhoods of fatigue cracks observed in aluminum specimens produced by laser powder bed fusion. The second thrust will focus on numerically characterizing the local micromechanical fields that evolve in 3D as a function of underlying, manufacturing-induced microstructure and defect distribution, with particular focus on residual-stress incompatibility, porosity, and surface roughness. Data-driven approaches will be leveraged across the experimental and numerical data sets to provide new insights into the mechanisms responsible for fatigue failure among the specimens. While the research focuses on aluminum alloys, it is anticipated that the findings regarding the relative importance of geometrical defects, like pores and surface roughness, versus intrinsic material defects on fatigue failure of additively manufactured parts could be broadly applicable to other metals as well.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.