Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology. Characterization of failure processes of complex internal geometries and defects in metal AM can significantly enhance this understanding. We aim to demonstrate a complete experimental measurement process and failure analysis method to study the effects of AM defects. We utilized simultaneous implementation of tensile tests with high-resolution X-ray computed tomography (XCT) measurements on 17–4 stainless steel dog-bone samples with an intentional octahedron-shaped internal cavity included in the gauge length and also containing much smaller lack-of-fusion (LOF) defects, all generated by a Laser Powder Bed Fusion (LPBF) additive manufacturing process. The LOF defects were introduced by intentionally changing the LPBF default processing parameters. XCT image-based linear elastic finite element (FE) simulations were used to interpret the data. The in-situ tensile tests combined with simultaneous XCT measurements revealed the details of the failure process initiated by additively manufactured rough internal surfaces and porous defect structures, which experienced high stress concentrations. Progressive collapse of ligaments leading to larger pores was clearly observed, and the resulting porosity evolution until failure was quantitatively analyzed. The high stress concentrations were also directly confirmed by the FE simulations. The experimental methods described in this paper enable the quantitative study of the complex failure mechanisms of additively manufactured metal parts, and the image-based FE simulation method is effective for identifying and/or confirming possible failure locations and features.

中文翻译：

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研究人工内部缺陷对激光粉末床熔合 17-4 不锈钢样品拉伸行为的影响：同步拉伸测试和 X 射线计算机断层扫描

没有足够的数据可以充分了解金属增材制造 (AM) 缺陷对广泛采用新兴技术的影响。表征金属增材制造中复杂内部几何形状和缺陷的失效过程可以显着增强这种理解。我们旨在展示一个完整的实验测量过程和故障分析方法，以研究 AM 缺陷的影响。我们利用高分辨率 X 射线计算机断层扫描 (XCT) 测量同时实施拉伸测试，对 17-4 个不锈钢狗骨样品进行测量，标距长度中包含有意设计的八面体形内腔，并且还包含更小的缺陷融合 (LOF) 缺陷，全部由激光粉末床融合 (LPBF) 增材制造工艺产生。LOF 缺陷是通过故意更改 LPBF 默认处理参数引入的。基于 XCT 图像的线性弹性有限元 (FE) 模拟用于解释数据。原位拉伸测试与同步 XCT 测量相结合，揭示了由增材制造的粗糙内表面和多孔缺陷结构引发的失效过程的细节，这些结构经历了高应力集中。清楚地观察到导致更大孔隙的韧带逐渐塌陷，并定量分析了导致孔隙率演变直至失效的情况。有限元模拟也直接证实了高应力集中。本文中描述的实验方法能够定量研究增材制造金属零件的复杂失效机制，