The multiaxial fatigue behavior of Ti6Al4V samples, made by selective laser melting (SLM) process, was investigated in this work. Fatigue tests were carried out under three different loading conditions: (i) tensile, (ii) torsion, and (iii) in-phase axial–torsional. A modified damage model, based on the Sines criterion, is proposed and used to analyze proportional multiaxial fatigue data. Preliminary results showed that the proposed version provides a better prediction with respect to the Sines model. Infrared thermography and digital image correlation were also used to capture both temperature and strain evolutions during fatigue tests. Fatigue results highlighted different failure modes due to surface crack initiation and internal crack initiation, as also demonstrated by scanning electron microscopy of the fracture surface.

中文翻译：

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SLM Ti6Al4V合金在不同载荷条件下的多轴疲劳行为

在这项工作中研究了通过选择性激光熔化 (SLM) 工艺制成的 Ti6Al4V 样品的多轴疲劳行为。疲劳试验在三种不同的载荷条件下进行：（i）拉伸，（ii）扭转，和（iii）同相轴向扭转。提出了一种基于正弦准则的修正损伤模型，并用于分析比例多轴疲劳数据。初步结果表明，所提出的版本对正弦模型提供了更好的预测。红外热成像和数字图像相关也被用来捕捉疲劳测试过程中的温度和应变演变。疲劳结果突出了由于表面裂纹萌生和内部裂纹萌生导致的不同失效模式，断裂表面的扫描电子显微镜也证明了这一点。