PSI - Issue 60

26 Sreerag M N et al. / Procedia Structural Integrity 60 (2024) 20–35 Sreerag M N/ Structural Integrity Procedia 00 (2023) 000 – 000 simulate the axial load, one axial face of the model is fixed in axial direction whereas at the other face, axial load corresponding to meridional stress is applied. A typical FE model is shown in fig. 1.

4.1.1. Interpretation of FE results of long seam weld model

 The FE results are summarized in the Table-3. In all cases, the failure is by net section yielding.  In the model simulating the weld and parent metal properties, failure is in the in the weld region.  In the conservative model, the failure pressure reduces from 97.37 ksc to 79.68 ksc when R2 weld repair properties are considered. i.e. failure pressure reduces by 22.22 %.  In the model simulating the weld as well as the parent metal properties, the failure pressure reduces from 97.37ksc to 80.69 ksc when there is R2 weld repair. i.e. failure pressure reduces by 20.67 %. Failure pressure is found to increase by 1.26 % when we exactly model the weld and parent metal properties.

Table 3: Comparison of FE computed failure pressure for different cases of long seam weld FE Model with uniform properties at shell region and L/s weld region (Conservative)

FE model with parent metal properties in shell and weld properties at L/s weld region (Realistic)

Property

Failure pressure (ksc)

% diff. with respect to PM failure pressure

L/s weld region

Failure pressure (ksc)

% diff. with respect to PM failure pressure

PM

97.37 90.97 88.80 79.68 76.80

-

-

-

-

R0 R1 R2 R3

7.03 9.65

R0 R1 R2 R3

92.00 90.05 80.69 77.50

5.83 8.12

22.22 26.78

20.67 25.63

Fig 2: Schematic showing hoop load shared by weld and parent metal In reality, the circumferential (hoop) load is shared by two circumferential areas. One area is having properties of parent metal whereas the other area is having the properties of weld material as shown in fig-2 above. When we consider the conservative approach, both resisting circumferential areas will have the properties of weld material and on account of this burst pressure reduces. This conservative case is not realistic. In reality, hoop load is shared by parent metal (in shell) and weld material (at weld), hence the failure pressure increases. Table 4 summarizes the results of the analysis carried out. An increase in failure pressure due to this load sharing by the parent metal is seen.