PSI - Issue 68

M. Mahatab et al. / Procedia Structural Integrity 68 (2025) 815–821 M. Mahatab and R. Ranjan / Structural Integrity Procedia 00 (2025) 000–000

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The SCF variation along the depth is obtained by linear elastic finite element modelling of cruciform joints in Abaqus, as shown in Figures 1 (b) and (c). The stress concentration is obtained along the thickness direction (normal to the loading direction) at around 300 points.

(a)

(b)

(c)

Figure 1: (a) component geometry of the cruciform joint ; (b) FEM model of the cruciform joint; (c) SCF variation along the normalized depth

The non-uniform residual stress distribution for as-welded and HFMI-treated cruciform welded joints was adopted from Ranjan and Walbridge (2021), which was fitted through the extensive experimental data points collected from existing literature. The fitted residual stress distribution for as-welded and impact-treated cruciform joints is shown in Figure 2 (a) and Figure 2 (b), respectively. The maximum value of residual stress was assumed to vary between -0.2 σ y to 1.5 σ y in the case of an as-welded cruciform joint and -1.7 σ y to 0.3 σ y for the impact-treated cruciform welded joint.

(a) (b) Figure 2: (a) Fitted residual stress distribution for as-welded cruciform joint; (b) for impact-treated cruciform welded joint (Ranjan and Walbridge (2021)) Three different loading histories were used in the SBFM analysis, namely constant amplitude (CA) with a load ratio ( R ) of 0.1, variable amplitude history 1 (VA1), and variable amplitude history 2 (VA2) adopted from Ghahremani et al. (2015) as shown in Figure 3. 4. Results and discussion The results of the deterministic SBFM model can be seen in Figures 4, 5, and 6 for S550MC grade steel. The prediction was made for as-welded and HFMI-treated weldments for three loading conditions, i.e. constant amplitude (CA) and variable amplitude (VA1 and VA2) loading, with the assumption of initial defect with semi elliptical shape. For CA loading, two bounds, i.e. upper and lower bound, correspond to residual stress 0.2 σ y and 1.5 σ y are considered for predictions. Fatigue test data for as-welded S550MC grade steel under CA loading from the three published journals (Ellerbeck (2023); Lindqvist (2002); Gustafsson (2006)) were also plotted along with SBFM predictions for comparison purposes. The specimen geometry used for the prediction was similar to that used in Ellerbeck (2023), Lindqvist (2002), and Gustafsson (2006). For impact-treated conditions, no fatigue test data is