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

相加制造(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，它可以在复杂金属部件的生产中提供更多的灵活性和效率。然而，在结构部件必须承载载荷(在某些情况下，部件必须长时间承受重复载荷)的应用中，AM作为一种可行且安全的替代方案处于关键节点。这一变革性制造技术的广泛结合受到以下事实的阻碍：目前无法预测添加制造的金属部件何时以及为什么会发生故障，并相应地设计该部件以降低故障风险。对于许多希望使用AM生产金属承载部件的行业来说，这是一个主要问题。该学院早期职业发展计划(Career)奖支持基础研究，以满足这一迫切需求，并使金属AM在许多行业中得到更广泛、但又安全的使用，包括航空航天、汽车、生物医学、制造和国防。这项研究与一个独特的推广计划紧密结合在一起，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。该职业奖支持的研究是通过在附加制造的铝中发现3D、微结构敏感、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。将进行两个平行的研究推进。其中一个重点将集中在实验上表征激光粉床聚变产生的铝试件中观察到的疲劳裂纹的3D邻近区域的微观结构特征。第二个重点将集中在数字表征作为潜在的、制造诱导的微结构和缺陷分布的函数在3D中发展的局部微机械场，特别关注残余应力不相容、孔隙率和表面粗糙度。将在实验和数值数据集上利用数据驱动的方法，以提供对导致试件疲劳失效的机制的新见解。虽然这项研究的重点是铝合金，但预计有关几何缺陷(如气孔和表面粗糙度)与固有材料缺陷对附加制造部件疲劳失效的相对重要性的研究结果可能也广泛适用于其他金属。该奖项反映了NSF的法定使命，并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。

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.