PSI - Issue 42

6

Jochen Tenkamp / Structural Integrity Procedia 00 (2019) 000 – 000

Jochen Tenkamp et al. / Procedia Structural Integrity 42 (2022) 328–335

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Fig. 3. (a) Quasi-static and (b) cyclic stress-strain curves of sand cast (SC) and additively manufactured (AM) alloys.

3.2. Fatigue behavior The fatigue behavior is characterized by S-N curves in Figure 4a. Run-outs are marked by arrows and crossed symbols. Nevertheless, AM and SC materials had comparable initial defect sizes, AM-10 shows a significantly reduced fatigue performance in the LCF and HCF regime. SC-10 and SC-7 have comparable LCF strength while the HCF strength is reduced for SC-7. The comparable fatigue strength at higher loading of SC-10 compared to SC-7 can be related to the embrittlement effect of Si precipitates and the reduced strain tolerance of Si precipitates.

Fig. 4. (a) S-N and (b) relative S-N diagrams of sand cast (SC) and additively manufactured (AM) alloys. In Fig. 4b, the estimated fatigue strength a ∗ L,1E7 according to Murakami-Noguchi (Tab. 1) is evaluated in relative S-N diagram, where the stress amplitude is related to a ∗ L,1E7 . The fatigue strength could be estimated well for SC alloys, as no failure happened at relative stress amplitudes lower than 1. Several specimens of AM-10 failure at relative stress amplitudes significantly lower than 1. This means, that the Murakami-Noguchi concept leads to a significant overestimation of fatigue strength for AM material and that the defect size and hardness is not enough for a sufficient estimation.