Thermomechanical and Powder Sintering Aspects in Electron Beam Additive Manufacturing - Applications to Overhang Support Designs

本研究的目的是改进粉末床电子束增材制造（EBAM）中零件悬垂几何形状的支撑结构设计。据推测，烧结粉末的导热性差是零件缺陷的根本原因，如与零件悬垂（或类似）几何形状相关的翘曲。因此，从承重的角度来看，所要求的支撑结构的功能不是；相反，在功能支撑设计中，应研究EBAM过程中复杂的热力学现象，这些现象会导致残余应力和变形。具体来说，本研究将表征烧结粉末的孔隙率及其对热性能的影响，开发有限元热力学模拟，结合孔隙率相关的热性能，用于EBAM的温度和应力预测，评估EBAM中悬垂几何对零件热力学行为的影响，以及与翘曲严重程度的关联，并研究不同的支撑模式，以评估设计支架的有效性。本研究的结果将通过改进和有效的支撑结构来提高EBAM技术的性能和有效使用。因此，该项目将直接使金属增材制造（AM）技术的用户受益，加强国家工业的全球竞争力。与EBAM的主要用户之一马歇尔太空飞行中心合作，研究小组可能会进一步应用研究结果来解决AM技术中存在的实际问题。此外，从本研究中获得的新工艺理解将有利于其他粉末基AM工艺的研究，如选择性激光烧结。此外，研究团队将与国家制造科学中心合作，将项目成果及时广泛地传播给AM行业。这项研究的进一步社会影响包括恢复高中学生对工程和技术的兴趣，特别是那些未被充分代表的群体。

The goal of this research is to renovate the support structure designs for part overhang geometries in powder-bed Electron Beam Additive Manufacturing (EBAM). It is hypothesized that the poor thermal conductivity of sintered powders is the root cause of part defects such as warping associated with part overhang (or similar) geometries. Hence, the required function of support structures is not from the weight-carrying standpoint; rather, the complex thermal and mechanical phenomena of the EBAM process, which lead to residual stresses and distortions, should be studied for functional support designs. Specifically, this research will characterize sintered powder porosity and its effects on thermal properties, develop finite element thermomechanical simulations incorporating porosity-dependent thermal properties for temperature and stress predictions in EBAM, evaluate overhang geometry effects on the part thermomechanical behaviors in EBAM and correlate with warping severity, and investigate different support patterns to evaluate the effectiveness of a designed support.The outcome of this research will enhance the performance and efficient usage of the EBAM technology through improved and effective support structures. Thus, the project will directly benefit the users of metal Additive Manufacturing (AM) technologies, strengthening the global competitiveness of the nation's industry. Collaborating with one of primary EBAM users, Marshall Space Flight Center, the research team may further apply findings to tackle pragmatic problems that exist in AM technologies. Moreover, new process understanding from this research will benefit studies on other powder-based AM processes such as selective laser sintering. In addition, working with the National Center for Manufacturing Sciences, the research team will disseminate the project results timely and widely to the AM industry. Further societal impacts of this research include reviving high school students' interest in engineering and technology, particularly, from underrepresented groups.