PSI - Issue 57

Kalle Lipiäinen et al. / Procedia Structural Integrity 57 (2024) 32–41 Lipiäinen et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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IN718 Unnotched IN718 Semi-circular notch IN718 V-notch (r = 1 mm) IN718 V-notch (r =0.1 mm) IN718 HT Unnotched IN718 HT V-notch (r = 1 mm)

4R reference stress range [MPa]

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Fig 6. Inconel 718 from (Solberg et al., 2020; Solberg & Berto, 2019) in (a) nominal stress (b) 0.04 mm TCD – based 4R method (Scatter range shown as in Fig. 5b).

Combined data Fatigue data is presented in the nominal stress system in Figure 7a to highlight difference of notched IN718 and MS1 specimens in as-built condition in comparison to unnotched polished heat treated CX -specimen with horizontal build orientation representing the highest fatigue strength. Illustrating the original nominalstress data with geometric SCFs considered would be the first step to decrease the scatter. After following introduced fatigue strength assessment procedure, Figure 7b illustrates the 4R method reference data ( Δσ k,ref ) and the presented data could be used as C (fatigue capacity) and m (slope) parameters in fatigue strength assessment enabling comparison with various geometrical SCFs, surface characteristics and build qualities. It can be concluded that print quality based on equivalent crack length based together with geometrical SCFs results reasonable scatter and possibility to assess fatigue performance on single FAT class. Low strength of 316L specimens’ limits fatigue performance under 10 5 cycles, which should be considered in component design.

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MS1_UN MS_EV1 MS1_EV2 MS1_EC1 MS1_EC2 MS1_IV1 MS1_IV2 MC1_IC1 MS1_IC2 CX_VM CX_VA CX_HTHM CX_HTVM CX_HTVA 316L_HM 316L_VM 316L_VA 316L_VHFMI

Yield strength

Inconel_UN Inconel_SC Inconel_V1mm Inconel_V0.1mm IN 718 HT UN IN718 HT V1mm

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Fig 7. Data for studied 316L, CX, MS1 and IN718 SN-data in (a) nominal (net cross section) stress method and (b) 0.04 mm TCD – based method.