PSI - Issue 53

Rainer Wagener et al. / Procedia Structural Integrity 53 (2024) 151–160 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4: Distributions of defects in notches depending on the up- and down-skin conditions.

Considering the discussion above it is not surprising that the rim zone of the notch geometries differs depending on the built orientation. In case of full-up-skin condition the surface is smooth and only a few small pores are present. In contrast to this, under down-skin conditions density of pores as well as their sizes increase. Due to the required support structures the surface roughness increases even after they have been removed. Because of this, the resulting fatigue strength differs and depends on the local exposure strategy, Fig. 5. Within the same built to load orientation a higher stress concentration leads to a lower fatigue strength, as expected. But with a change of the built to load orientation another distribution of defects must be considered, which leads to a different fatigue strength.

Fig. 5: SN-curves for different notch geometries and built to load orientations.

Due to the influence of the additive manufacturing process on the local microstructure and its properties, and with respect to the fatigue approach of cyclically loaded structures, it is not sufficient to consider only the nominal notch geometry. On the other hand, it is important to take into account the combination of nominal notch geometry and build orientation as well as the exposure strategy for the derivation of fatigue properties.