PSI - Issue 75

Luca Vecchiato et al. / Procedia Structural Integrity 75 (2025) 602–608 Luca Vecchiato et al. / Structural Integrity Procedia (2025)

604

3

λ= Δ 2 , , Δ 2 , ,

(4)

The selection of the appropriate design curve is guided by the criteria reported in Table 1, which considers both the biaxiality ratio λ (Eq. (4)) and the thickness t of the main structural element (plate or tube). Although the PSM formulation for multiaxial VA loading has already been extensively validated through numerous experimental data on arc-welded steel joints [14,16], and a validation under pure mode I loading for aluminium arc-welded joints is available in the literature [17], this work represents the first application of the method to multiaxial VA data for arc-welded joints made from aluminium alloys.

Table 1: Criteria for selecting the reference PSM-based design curve for aluminium arc-welded joints. [4]

T [mm]

λ Eq. (3)

Δσ eq,peak,A,97.7% [MPa]

Δσ eq,peak,A,50% [MPa]

k [-]

T σ [-]

N A [cycles]

T ≥ 5 mm T ≥ 5 mm

λ = 0 λ > 0 λ ≥ 0

2∙10 6 2∙10 6 2∙10 6

92 92 92

123 123 123

3.8 6.5 6.5

1.80 1.80 1.80

3 mm ≤ T < 5 mm

2. Validation against experimental data Kueppers and Sonsino [18] fatigue tested tube-to-flange full penetration TIG- and MIG-welded joints (Figure 1) made from extruded and peak aged (T6) AlSi1MgMn (EN AW 6082). Specimens were tested in the as-welded state under in-phase ( φ = 0°) and out-of-phase ( φ = 90°) combined bending and torsion loading.

CRACK INITIATION POINT (Weld Toe)

Fixed region

2 α =135 °

z=16

t =10

ρ =13mm

22 n ° 8holes

Fig. 1. Specimen geometry. Constant Amplitude and Variable Amplitude combined bending and torsion loads were applied with a nominal biaxiality ratio = / = 1/√3 , τ a and σ a being the nominal shear and bending stresses, respectively. Concerning VA tests, a Gaussian spectrum with a length of L s = 5∙10 4 cycles was discretized into sixteen steps (Figure 2) which