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. 1: Typical sections of structures for different notch geometries

The test results of AlSi10Mg specimens in the as-build state are depicted in Fig. 2, including the results of unnotched and notched specimens with the stress nominal concentration factor K t = 1.7 and K t = 2.3. In the case of the unnotched specimens the results of both the strain- and the force-controlled fatigue test series are depicted. It seems that these test results are complementary to each other. Regarding the two tests series of notched specimens, the resulting SN-curves differ. As expected, the fatigue strength of the specimens with the higher nominal stress concentration factors is lower. Unnotched specimens do not fulfill the expectations, because these results coincide with the SN-curve of the notched specimens with the lower nominal stress concentration factor.

Fig. 2: Fatigue test results of AlSi10Mg specimens with different stress notches cyclically loaded in built direction.

Regarding the microstructure, including the process-related defects, this fatigue behavior is not surprising, because the geometrically unnotched specimens are not sound and therefore local stress concentrations can occur, which will have an impact on the fatigue. To clarify the influence of defects, that means pores, on the stress-strain state, a linear elastic load simulation using finite elements has been performed. Therefore, two FE-models have been setup with respect to the symmetrical conditions to reduce the numerical effort, Fig. 3. The first one represents the nominal (ideal) CAD geometry (lower half of Fig. 3) and the second one the real geometry of an additively manufactured structure (upper half of Fig. 3). The second one has been scanned and imported into the FE-model. In both cases homogeneous strength distributions are assumed.

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