PSI - Issue 57

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

38

7

2000

2000

a

b

MS1_UN MS_EV1 MS1_EV2 MS1_EC1 MS1_EC2 MS1_IV1 MS1_IV2 MC1_IC1 MS1_IC2

MS1_UN MS1_EV1 MS1_EV2 MS1_EC1 MS1_EC2 MS1_IV1 MS1_IV2 MS1_IC1 MS1_IC2

Yield strength

Yield strength

Reference stress ( a = 0.1 mm) [MPa]

CX_VM CX_VA Reference stress ( a = 0.04 mm) [MPa] CX_HTHM CX_HTVM CX_HTVA 316L_HM 316L_VM 316L_VA 31260L0_VHFMI

CX_VM CX_VA

CX_HTHM CX_HTVM CX_HTVA

316L_HM 316L_VM 316L_VA 316L_VHFMI

200

10 000

100 000

1 000 000

10 000

100 000

1 000 000

Fatigue life

Fatigue life

Fig 5. TCD-based 4R modified fatigue test results (a) 0.1 mm and (b) 0.04 mm critical distance. Scatter band illustrated based on data (Lipiäinen, Ahola, Kaijalainen, et al., 2022). High-strength materials show consistent fatigue performance in the 4R reference stress system However, analysis was extended for low-strength 316L L-PBF specimens. 316L components, build in the vertical direction and tested in as-built condition series in high cycle -regime is starting to form own trend which is the result of increased initial crack length. Generally, the presented 4R method was found beneficial. In future studies, a material strength dependence for the master curve should be introduced as the low-strength specimens fall below high-strength specimens both categories still showing consistent ranges. IN718 Fatigue test results from Solberg & Berto (2019) and by Solberg et al. (2020) were evaluated with presented 4R method. Studies by Solberg et al. feature detailed and well documented fractography enabling results re-analysing. Crack was modelled at the notch root to apply TCD-based 4R method even tough fatigue failure typically occurred in overhang sections. This approach simplifies FEA including quality parameter. Interest towards Inconel 718 in AM-components has increased and fatigue strength assessment is a key issue in high-performance components.Figure 6 illustrates two IN718 test series with scatterbands based on previous work. Furthermore, with decreased 0.04 mm stress obtaining distance, the fatigue performance is in line with conventional and AM -steel components. Stress obtaining distance of 0.1 mm was tested and the IN718 fell below characteristic curve.

Table 3. IN718 fatigue analysis data.

Initial crack length ( μ m)

Material

Specimen Unnotched 100 Semicircular V-notch r = 1

100 150 225

IN718 IN718 IN718 IN718

V-notch r = 0.1 225

Unnotched

IN718 HT IN718 HT

125 200

V-notch r = 1