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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2. Joint geometry and experimental fatigue results In a previous work by some of the present Authors (Pelizzari et al. 2024), two different steel welded joint geometries used in off-road vehicles were subjected to fatigue testing under axial loads. Figure 1 shows that the joints were consisting of a pipe that penetrates a plate through four intermittent fillet welds. Each fillet weld generated two weld toe lines, namely the ‘plate - side’ and ‘tube -side ’, and two weld root lines, due to a 0.6 mm radial backlash between the tube and the plate hole, again classified as ‘plate - side’ and ‘tube -side ’ (see Figure 1) . The two joint configurations include one with the four intermittent fillet welds oriented perpendicular (transverse geometry) and another with the welds aligned parallel (longitudinal geometry) to the load direction. The local geometry of the weld ends was idealized in (Pelizzari et al. 2024) to simplify the geometric modeling phase in FEM simulations. To achieve this, the transverse triangular cross-section of the weld bead has been revolutionized around the r-axis depicted in Figure 1, which is defined as parallel to the hypotenuse and intersects the catheti of the weld bead section. The fatigue tests were conducted under axial loading with adopting a nominal load ratio of R = 0.05 and using an MFL servo-hydraulic axial machine with a load capacity of 250 kN, controlled by an MTS TestStar IIm. A technical crack initiation criterion was established at a 0.1 mm increase of the maximum displacement of the actuator; while run out condition was defined at 2 million cycles, if no crack initiation occurred.

Z

Y

X

Z

X

Y

Y

Z

X

SECTION A-A

LONGITUDINAL WELDED JOINT (L)

TRANSVERSE WELDED JOINT (T)

r - axis

Y

Z

X

Y

Z

X

(a)

t t

(b)

z

Z

TUBE

Tube-side weld root

X

Plate-side weld root

Y

2  = 135°

Tube-side weld toe

2  = 135°

2  = 90° 0.6 mm

2l

t p

Plate-side weld toe

PLATE

Fig. 1: Nominal geometry and main geometric parameters of the (a) longitudinal and (b) transverse joints with intermittent fillet welds having idealized weld ends. 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 .