PSI - Issue 75

Kalle Lipiäinen et al. / Procedia Structural Integrity 75 (2025) 19–28 Lipiäinen et. al. / Structural Integrity Procedia (2025)

26 8

3.2. Fatigue test results

The fatigue test results show one test series with increased performance: the EOS G-series had the highest fatigue performance. The fatigue performance of the test series with other finishes were uniform. The critical locations are shown in as subfigures in Fig 9. Using local stresses obtained by FEA for the critical locations, the results significantly change. The SCF in EOS G series is significantly higher than in other test series. The results of the EOS G series follow FAT 500 MPa m = 5, and FAT 250 MPa m = 3 for other test series. The change in the slope parameter also indicates increased manufacturing quality.

a

b

2000

100

Detailof G-test series crack propagation

EOS G EOS S SLM B SLM W

EOS G EOS B SLM B SLM W

Force range [kN] R = -0.66

Local stress range [MPa] R = -0.66

200

10

10 000

100 000

1 000 000

10 000

100 000

1 000 000

Fatigue life [cycles]

Fatigue life [cycles]

Fig 9. Fatigue test data illustrated as (a) force ranges and (b) stress ranges

3.3. Fractography Local quality was characterized with the SEM and fractography is illustrated in Fig. 10 with notes on quality. The findings on the increased fatigue performance in the EOS G test series was supported by surface quality analysis inside the component. Furthermore, critical notch area shows higher deformation due to the shot blasting with full coverage. The fractography revealed differences in the local quality. The critical detail in EOS G test series was glass peened and downward facing notch (against build direction) was critical due to decreased surface quality. In other test series, significant imperfections were observed in top edge of the component. SLM B series show the effect of peening on critical location. In EOS S and SLM W series, the powder particles attached to surface can be still seen.

SLM B -series

EOS S -series

EOS G -series

Peened surface Waviness and powder particles visible

Powder particles visible on surface

Peened surface Powder particle

Crack propagation

Imperfection

Crack propagation

Upward facing notch

Mechanical contact on surface

Downward facing notch

Sub-surface imperfection

Sub-surface imperfection

Different failure mode than other series

Crack propagation

Fig. 10. Fractography showing quality and crack propagation in critical locations.