Multiaxial fatigue behavior of SLM Ti6Al4V alloy under different loading conditions

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.