Issue 75

V. Thondamon et alii, Fracture and Structural Integrity, 75 (2026) 88-103; DOI: 10.3221/IGF-ESIS.75.08

Figure 2: Stress-strain curve of weld material.

The geometric specifications of the pipe specimens are presented in Tab. 1 [18–19]. A schematic diagram of a straight pipe containing a circumferential through-wall notch in the weld is shown in Fig. 3. The specimens were loaded under four-point bending under monotonic loading. Each of the three pipes featured a circumferential through-wall notch in the weld. The nominal outer diameters of the pipes were 168 mm, 171 mm, and 325 mm. Their lengths ranged from 1996 mm to 4960 mm. The average wall thicknesses varied between 14.6 mm and 25.7 mm, and the notch lengths after fatigue pre-cracking were approximately between 90 mm and 170 mm. All notches had an angle of approximately 60°. The pipe specimens considered in the present study were Post Weld Heat Treated (PWHT) to remove the residual stresses. Hence, residual stresses are not considered in the structural integrity assessment.

Notch angle 2 ( o ) 62.8

Pipe diameter (mm)

Pipe thickness (mm)

Pipe length (mm)

Notch length 2c (mm)

Specimen No.

SP6-60-TWC-SSW-M1

168 171 325

14.79

2022 1996 4960

92 90

SSPW6-25 SSPW12-27

14.6 25.7

59.9 59.8

170

Table 1: Geometric specifications of the pipe specimens.

Section A-A Figure 3: Schematic diagram of a straight pipe containing a circumferential through-wall notch in the weld.

Before conducting the fracture experiments, all pipe specimens were subjected to fatigue pre-cracking to generate a sharp crack front. Fig. 4 shows the experimental set-up used for this pre-cracking. Fatigue pre-cracking was performed using a ±1000 kN capacity actuator under four-point bending and constant amplitude sinusoidal loading was applied until at least 2 mm of crack growth was achieved at both notch tips along the circumferential direction. Fig. 5 shows a schematic of the fracture test set-up. Fig. 6 shows a close-up view of the experimental set-up. The specimens were subjected to displacement controlled loading using servo-hydraulic actuators with capacities of ±1000 kN and ±2000 kN. During the fracture tests,

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