Additive manufacturing (AM) enables the fabrication of lattice structures with optimal mechanical, fluid, and thermal properties. However, during the AM fabrication process, defects are produced in the strut and node elements, which comprise the lattice structure. This leads to discrepancies between the AM fabricated lattice and its idealized computer-aided design (CAD) model, negatively affecting the ability to predict the mechanical behavior of the fabricated lattice via numerical models. Current research is focused on quantification of geometric uncertainties in the strut elements of the lattice; as-manufactured node geometries remain relatively unexplored on an individual scale, despite their criticality to the mechanical response of the structure. Understanding the geometrical properties of as-manufactured nodes relative to CAD idealizations can be used to improve lattice designs and numerical models. In this research, X-ray microcomputed tomography (μCT) is used to analyze and quantify the as-manufactured nodal geometry, found in face-centered cubic and face-centered cubic with axial struts lattices fabricated via selective laser melting. A custom tool is developed that enables auto-isolation and classification of nodal joints from μCT-derived cross-sectional slices. Geometrical properties are extracted from the isolated nodal cross sections and compared with their idealized CAD model counterpart. Quantification of geometrical defects provides insight into how nodes within an AM lattice structure differ from each other and their idealized design. Overall, this research is an initial step toward developing accurate and efficient numerical models, as well as better node design for AM.

中文翻译：

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增材制造晶格结构中基于图像的节点几何表征

增材制造 (AM) 可以制造具有最佳机械、流体和热性能的晶格结构。然而，在 AM 制造过程中，在构成晶格结构的支柱和节点元素中会产生缺陷。这导致 AM 制造的晶格与其理想化的计算机辅助设计 (CAD) 模型之间存在差异，从而对通过数值模型预测制造的晶格的机械行为的能力产生负面影响。目前的研究主要集中在格子的支柱元素中几何不确定性的量化；尽管制造节点的几何形状对结构的机械响应至关重要，但在单个规模上仍然相对未被探索。了解制造节点相对于 CAD 理想化的几何特性可用于改进晶格设计和数值模型。在这项研究中，X 射线显微计算机断层扫描 (μCT) 用于分析和量化制造的节点几何形状，这些几何形状存在于通过选择性激光熔化制造的面心立方体和具有轴向支柱晶格的面心立方体中。开发了一种自定义工具，可以从 μCT 衍生的横截面切片中自动隔离和分类节点关节。从孤立的节点横截面中提取几何特性，并与理想化的 CAD 模型对应物进行比较。几何缺陷的量化可以深入了解增材制造晶格结构中的节点如何彼此不同以及它们的理想化设计。总体，