PSI - Issue 57

Okan Yılmaz et al. / Procedia Structural Integrity 57 (2024) 420 – 427 Yılmaz and van Hoecke / Structural Integrity Procedia 00 (2023) 000–000

424

5

Laser-cut 14-mm-φ

Punched 13-mm-φ, c=0.05 mm

Punched 18-mm-φ, c=0.4 mm

S700MC

S700MC (DURAMECH)

S700MC

8 mm

8 mm

5 mm

6

6.5

7

6.5

7

7.5

8.5

9

9.5

Distance from centerline (mm)

Distance from centerline (mm)

Distance from centerline (mm)

Punched 13-mm-φ, c=0.05 mm

Laser-cut 14-mm-φ

Punched 18-mm-φ, c=0.4 mm

S960MC

S960MC

S960MC (DURAMECH)

6 mm

5 mm

6 mm

6

6.5

7

6.5

7

7.5

8.5

9

9.5

Distance from centerline (mm)

Distance from centerline (mm)

Distance from centerline (mm)

Fig. 3. Hole measurements of fatigue samples in comparison to the theoretical hole cross-section denoted with dashed lines. Punched holes with low clearance, c = 0 . 05 mm locate at the left and laser-cut holes at the middle. 3D profile measurements are given within the plots as additional visual. For comparison, punched holes with a higher clearance, c = 0 . 4 mm of the DURAMECH project (Debruyne et al., 2019) are given at the right.

Figure 4 presents fatigue results of axially loaded fatigue tests with a hole. For both materials, it is seen that at infinite-limit regime, the fatigue performance surpasses the suggested design curves (FAT80 with m = 5 and FAT90 withm = 3) and the slope m = 5 fits the data much better. FAT160 with m = 5 is attainable even with the punched holes and without any burr removal. While, for S700MC, the laser-cut and punched data points are comparable, for 960MC, the samples with a punched hole had a lower fatigue strength compared to the laser cut ones, although it is still above FAT160 design curve. The results show that the S960MC grade is less tolerant in fatigue to punching defects. No direct correlation was found between the roughness values and the fatigue results. When a clearance value of c = 0 . 4 mm is used (Debruyne et al., 2019), it resulted in rough and damaged holes and FAT80 design line remained the norm. Figure 5 summarizes four-point bending fatigue tests. The presence of samples prepared by water-jet cutting in stead of milling was not intentional but provides insight with a few data points about the performance obtained with this cutting technique. S700MC demonstrated similar fatigue performance of laser-cut and milled faces while milled cut-edges of S960MC resulted in better fatigue performance compared to laser-cut and water-jet faces. This result displayed that S960MC is less tolerant to defects than S700MC.