Abstract
Additive Manufacturing (AM) is undoubtedly of high potential to fulfil the needs of modern digital manufacturing, however, the failure prediction of the components made by this technique is still a challenging task due to uncertainty in their structural properties. Different geometries and build orientation of AM parts results in various surface roughness and residual stresses and consequently various mechanical properties. Regardless of the type of laser AM technique (Direct Energy Deposition (DED), Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), etc.), the AM components are usually subjected to heat treatments in order to eliminate the residual stress and improve metallurgical characteristics, and to surface treatments to decrease their roughness. Although rarer, the cases in which the specimens are tested as-built, are considered extremely necessary in order to quantify the quality of machine molding and the set of parameters used, as well as the validity of any other subsequent treatment. For these reasons, the following work aims to examine the experimental results of the fatigue behavior for as-built specimens produced with Ti-6Al-4V powders through the DMLS additive production technique with optimized parameters, using two different build directions. The two different behaviors will be compared. In particular, attention will be focused not only on the results obtained from the experimental fatigue tests but, through a scanning electron microscope (SEM), the single fracture surfaces will be investigated and in conclusion considerations on the residual stress state will be made. All the results will be use in order to determine and correlate the causes to the different fatigue behavior. The results obtained can be used as a starting point for the performance quantification of subsequent treatments or more simply be used in the design phase.
Published Version
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