PSI - Issue 75

Lucrezia Contiero et al. / Procedia Structural Integrity 75 (2025) 609–615

612

4

Author name / Structural Integrity Procedia (2025)

Mechanical Properties

Yield stress [MPa]

510

414

AM base material

Strength [MPa]

619

629

Strain %

42.2

-

Yield stress [MPa]

n.a.

326

Wrought base material

Strength [MPa]

n.a.

631

Strain %

n.a.

55

n.a. = not applicable.

Fig. 1. Geometry of full-penetration butt-weld joints AM-AM of Braun et al.(Braun et al. 2023) and AM-WR of Selmi et al.(Selmi et al. 2023)

Table 2. Geometrical parameters of dissimilar and homogeneous full-penetration butt-weld joints made of 316L steel as defined in Fig.1

R [mm] [mm] [mm] [mm] [mm]

2 [°]

2 [°]

2 [°]

t [mm]

L [mm]

B [mm]

b [mm]

2α [°]

Reference Material

(Braun et al. 2023) (Selmi et al. 2023)

316 L AM-AM

4

140

140

n.a.

n.a.

0.6

0.6

3.3

3.9

162 149 149 162

316 L AM-WR

4

100

13

8

64

0.7

0.5

4.1

4.1

140 166 155 128

n.a. = not applicable.

2.1. Nominal Stress Approach The experimental results reported by Braun et al. (Braun et al. 2023) and Selmi et al. (Selmi et al. 2023) are expressed in terms of number of cycles to failure ( ) as a function of the applied nominal stress range, as illustrated in Fig. 2. In addition, the figure reports the fatigue design curve suggested by Eurocode 3 (Eurocode 3 2010) for steel full-penetration butt-joints with ratio 0.1 < h/ w ≤ 0.2, having FAT class of 80 MPa and inverse slope k = 3. The comparison between the two datasets reveals the following: • In the high-cycle fatigue (HCF) regime, the experimental data show higher fatigue strengths than those estimated by the Eurocode 3 design curve (Eurocode 3 2010) ; • A fatigue design curve was calibrated on the combined datasets by applying a statistical regression based on ISO 12107 recommendations (ISO 12107-2003). The fitted S – N curve, defined by an inverse slope k = 7.5 and a scatter index T σ = 1.50 (corresponding to a 2.3% – 97.7% survival probability scatter band), provides a more accurate representation of the experimental results. The derived endurance limit at 2 million cycles and 50% survival probability is equal to 184 MPa, considerably higher than the Eurocode 3 reference value, i.e. FAT 80.