PSI - Issue 66

Venanzio Giannella et al. / Procedia Structural Integrity 66 (2024) 71–81 Venanzio Giannella et al./ Structural Integrity Procedia 00 (2025) 000 – 000

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Table 1 summarizes the properties of the materials adopted for the tube and plate, the welding technology and the fatigue testing parameters. The reader is referred to Ref. (Pelizzari et al. 2024) for more details. The locations of crack initiation and their propagation paths were visually inspected in all tested joints. All transverse welded joints showed multiple sites of fatigue crack initiation, namely at the tube-side weld toe of the weld start (Figure 2c,d) and at the weld roots of the weld stop (Figure 2a,b), with cracks propagating through the tube. The tube-side weld toe was identified as the main crack initiation location due to its longer propagation path (for further details, see Ref. (Pelizzari et al. 2024)). On the other hand, all longitudinal welded joints exhibited crack initiation at the plate-side weld toe of the weld stop (Figure 2e), with propagation occurring through the plate. Table 1: Materials, welding technology, heat treatment and testing parameters of the welded joints tested in Ref. (Pelizzari et al. 2024). Geometry Material Yield strength [MPa] UTS [MPa] Thickness [mm] Welding technology Test condition + # tested specimens R # Crack initiation location Transverse (T) Tube 25MnCr6 Q&T^ 638 785 7.5 MAG AW 10 0.05 Tube side weld toe Plate S355JR 355 510 6 Transverse (T) Tube 25MnCr6 Q&T^ 638 785 7.5 MAG SR 10 0.05 Plate S355JR 355 510 6 Longitudinal (L) Tube 25MnCr6 Q&T^ 638 785 7.5 MAG AW 9 0.05 Plate side weld toe Plate S355JR 355 510 6 Longitudinal (L) Tube 25MnCr6 Q&T^ 638 785 7.5 MAG SR 9 0.05 Plate S355JR 355 510 6 ^ Quenched and Tempered, + AW = as-welded, SR = stress-relieved, # R = nominal load ratio

TRANSVERSE WELD BEADS

LONGITUDINAL WELD BEADS

Plate-side weld toe (WSp)

Weld root (WSp)

Tube-side weld toe (WSt)

(e)

(c)

(a)

(b)

(d)

Fig. 2. Fatigue cracks corresponding to the number of cycles at which technical crack initation occurred: (a) and (b) show fatigue cracks that originated at the weld root of the weld stop, while (c) and (d) illustrate fatigue cracks initiated at the tube-side weld toe of the weld start (T-AW n°8 joint:  F = 42 kN, N i = 1180953 cycles). Additionally, (e) shows a fatigue crack that initiated at the plate-side weld toe of the weld stop (L-SR n°2 joint:  F = 40 kN, N i = 623000 cycles). The images (b) and (d) reveal the (a) and (c) crack paths, respectively, analysed by dye penetrant inspections. Reproduced with permission from Pelizzari J, Campagnolo A, Dengo C, Meneghetti G (2024) Fatigue lifetime assessment of weld ends with idealized or real geometry in steel joints for off-road vehicles using the Peak Stress Method. Int J Fatigue 178:107964 .