PSI - Issue 18

Matilde Scurria et al. / Procedia Structural Integrity 18 (2019) 586–593 Matilde Scurria, Benjamin Möller, Rainer Wagener, Thilo Bein/ Structural Integrity Procedia 00 (2019) 000–000

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numerical simulation when a material-based fatigue approach, according to Hell et al. (2015), is chosen. For each build orientation and heat treatment, the cyclic stress-strain behaviour of Inconel ® 718 is macroscopically linear elastic for a maximum total strain of  a,t = 0.4%, while a plastic strain portion is visible for higher values of the maximum total strain.

a

b

c

d

e f Fig. 3. (a) Stabilized cyclic stress-strain behavior of Additively Manufactured Inconel ® 718 for a maximal strain amplitudes of 

a,t = 0.4% (a) XZ

and (b) Z,  a,t = 0.6% (c) XZ and (d) Z and  a,t = 0.8% (e) XZ and (f) Z.

The material, at  a,t = 0.4% (Figure 3a and 3b), presents a higher Young’s modulus of 200 GPa, when tested at 45° with respect to the build direction (XZ specimens), and a lower one of 177 GPa, when the load and build directions are aligned (Z specimens). At first, the reason of this could be attributed not only to the different build orientations, but also to a difference in terms of surface conditions. In fact, for the manufacturing of XZ specimens, support structures have been built and removed afterwards from the down-skin surface, resulting in a higher surface roughness, different microstructure and gradients of residual stresses due to asymmetrical cooling rates. However,