PSI - Issue 57

Inge Lotsberg et al. / Procedia Structural Integrity 57 (2024) 569–580 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

578 10

The integration of stresses through the thickness at the hot spot to derive the membrane stress and the bending stress gives a stress concentration factor equal to 1.336. Analysis no 4: By following the same methodology as for analysis no 1 the hot spot stress for Method A is derived as 1.342. For Method B the calculated hot spot stress is equal to 1.433. Effective notch stress method: The calculated stress at the weld toe in a notch stress analysis model resulted in a stress equal to 3.744 MPa. This corresponds to a hot spot stress equal to 1.498. A further discussion of this test result is given in Section 3.4. The calculated notch stress at the weld root resulted in a stress equal to 3.744 MPa.

1.8

1.7

1.6

Target + 10%

1.5

Target

1.4

1.3

Target – 10%

Hot spot stress (SCF)

1.2

1.1

1.0

Fig. 9. Measured and calculated hot spot stresses.

3.4. Analysis of the weld root

Fatigue assessment of the weld root can be performed by calculating the nominal stress in the weld throat and combine this stress by the W3 curve in DNV-RP-C203 (2019) which is the same as the FAT 36 curve in the IIW recommendations, Hobbacher (2009). Equilibrium of force in the direction of the doubling plate in Fig. 5 gives: = 1 2 √2( ⊥ + ⊥ ) (5) where a = throat thickness and t d = thickness of the doubling plate. The stress components are shown in Fig. 10. With also equilibrium in the normal direction to the doubling plate this gives: ⊥ = ⊥ = √ 1 2 (6) From DNV-RP-C203 (2019) the following equation is used to derive an equivalent nominal stress in the fillet weld: =√ ⊥2 + ⊥2 = (7)