This work aims to apply the Theory of Critical Distances (TCD) to the fatigue assessment of additively manufactured (AM) Ti-6Al-4V material produced via the selective laser melting (SLM) process. Modified alternatives to traditional TCD methods are considered. In this sense, it is sought to develop a fatigue prediction model that is better suited to assessing the impact of multiple stress-rising features which are located in close proximity to each other. Hereby, consideration has been given to modelling process-inherent surface roughness in combination with an internally positioned artificial defect, shaped as a feature that is reminiscent of a pore. Simultaneously, the research also seeks to circumnavigate a potential issue with respect to the current TCD methodology. This concerns the matter of applying TCD practices to components whereby the area of interest for conducting stress-distance analytics is on a size scale that is smaller than that of the critical distance length parameter itself. Several different strategies were attempted as a way to try and achieve meaningful modifications to the TCD process. Results show that it is possible to overcome such challenges that can often present themselves during the fatigue appraisal of AM metal parts. In this sense, the optimal novel strategy that was experimented with returned average error margins of 13.7% or better. It is anticipated that such models may assist in further optimising the accuracy of service life evaluation for metallic AM components that are intended for industry.

这项工作旨在将临界距离理论 (TCD) 应用于通过选择性激光熔化 (SLM) 工艺生产的增材制造 (AM) Ti-6Al-4V 材料的疲劳评估。考虑了传统 TCD 方法的改进替代方法。从这个意义上讲，寻求开发一种疲劳预测模型，该模型更适合评估彼此靠近的多个应力上升特征的影响。因此，已经考虑到建模过程固有的表面粗糙度与内部定位的人工缺陷相结合，形状为让人联想到孔隙的特征。同时，该研究还试图绕过与当前 TCD 方法有关的潜在问题。这涉及将 TCD 实践应用于组件的问题，由此进行应力距离分析的感兴趣区域的尺寸范围小于临界距离长度参数本身的尺寸范围。尝试了几种不同的策略来尝试对 TCD 过程进行有意义的修改。结果表明，有可能克服增材制造金属零件疲劳评估过程中经常出现的挑战。从这个意义上讲，经过试验的最佳新策略返回的平均误差率为 13.7% 或更高。预计此类模型可能有助于进一步优化用于工业的金属 AM 组件的使用寿命评估的准确性。