Selective laser melting (SLM) is one of the most promising additive manufacturing technologies for obtaining end-use components with excellent mechanical properties. However, the presence of manufacturing defects harms mechanical properties and fatigue performance. This work investigated the crack behaviour within an SLM Ti-6Al-4V alloy sample stressed with in-phase axial and torsional loading by X-ray computed μ-tomography (μ-CT). A sub-volume of material that contains the most significant defects was detected and analysed. The critical defect was identified by evaluating the effective strain intensity factor (SIF) using two different proposed models, that consider the effective area of a detected defect according to Murakami’s method. The first model is based on the modified Smith Watson and Topper (MSWT) criterion. The second is based on Liu’s virtual strain energy (VSE) method. The trend of the crack growth rate was obtained by measuring the effective area for a different number of cycles. The μ-CT data was also exploited to build a finite element model (FEM) of part of the gauge section containing surface defects. Finite element analysis (FEA) results have provided information on the stress state leading to high-stress concentrations at the crack tip influencing the propagation.

选择性激光熔化 (SLM) 是最有前途的增材制造技术之一，可用于获得具有优异机械性能的最终用途部件。然而，制造缺陷的存在会损害机械性能和疲劳性能。这项工作通过 X 射线计算机 μ 断层扫描 (μ-CT) 研究了受同相轴向和扭转载荷应力的 SLM Ti-6Al-4V 合金样品内的裂纹行为。检测并分析了包含最严重缺陷的材料子体积。关键缺陷是通过使用两种不同的建议模型评估有效应变强度因子 (SIF) 来识别的，这些模型根据 Murakami 的方法考虑了检测到的缺陷的有效面积。第一个模型基于修改后的 Smith Watson 和 Topper (MSWT) 标准。第二种是基于 Liu 的虚拟应变能 (VSE) 方法。通过测量不同循环次数的有效面积获得裂纹扩展速率的趋势。μ-CT 数据还被用于构建包含表面缺陷的部分仪表截面的有限元模型 (FEM)。有限元分析 (FEA) 结果提供了有关应力状态的信息，该应力状态会导致裂纹尖端处的高应力集中影响传播。