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

820

6

representing extension in width direction up to a normalized crack depth of about 0.62. A through-width crack was found as the final crack shape from the SBFM analysis for maximum stress levels below 225 MPa. A higher aspect ratio was observed for the higher maximum stress levels before the fracture of the specimen. In Figures 5(b) and 5(c), sudden net sectional failure was observed without the transformation of a semi-elliptical crack to a through width crack for variable amplitude loading conditions.

(a)

(b)

(c) Figure 5: Crack shape aspect ratio vs depth for CA loading (a); VA1 loading (b); and VA2 loading (c)

Figure 6 shows the SBFM prediction for impact-treated cases (Tr) and as-welded (AW) fatigue life curves for different loading conditions. Considerable improvement can be seen because of HFMI treatment in cruciform welded joints for all three loading conditions. The HFMI treatment substantially improves the fatigue life of welded joints, as predicted by the SBFM model, and supports the use of HFMI as an effective post-weld treatment for enhancing the durability of welded structures.

1000

100

CA-Tr VA1-Tr VA2-Tr

CA-AW VA1-AW VA2-AW

10

2,E+04 2,E+05 2,E+06 2,E+07 2,E+08 Nominal Stress Range (MPa) Number of cycle (N)

Figure 6: S-N curve for the as-welded and HFMI-treated case for different loading conditions

5. Conclusion Fatigue life predictions and crack growth analysis for S550MC steel grade were carried out using a strain-based