PSI - Issue 60

Sreerag M N et al. / Procedia Structural Integrity 60 (2024) 20–35 Sreerag M N/ Structural Integrity Procedia 00 (2023) 000 – 000

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6. Failure pressure of 3.2mm diameter maraging steel cylindrical shell In this section the failure pressure of dia 3.2m maraging steel cylindrical shell simulating the long seam weld, cirseam weld and T-joint with virgin properties and parent metal properties is estimated from FE. Conservatively a repair length of 100mm is also considered in the model.

6.1. No flaw failure pressure Following are the details of the model used: 

All long seam weld, T-Joint and cirseam weld are given virgin metal properties.  In the model, a repair length of 100mm in the axial direction and 40mm in the circumferential direction is considered for a repair in the long seam weld.  Similarly, a repair length of 100mm in the circumferential direction and 40mm in the axial direction is considered for a repair in the long seam weld.  Weld property at T-Joint is modelled Typical FE model used is shown in fig-6.

Fig 6: Typical FE model simulating the failure pressure of Ø3.2m M250 material cylindrical shell

Table 9 shows the comparison of failure pressure for different cases.

Table 9: Comparison of FE computed failure pressure for different cases Away from weld L/S weld joint C/S weld joint T-joint

Failure pressure (ksc)

PM PM PM PM PM PM

R0 R0 R0 R0

R0 R0

R0 R1 R1 R1 R1 R1

91.91 91.83 91.82 91.90 90.99 89.52

R0/Local R1 R0/Local R2 R0/ Local R2 R0/ Local R2

R0/ Local R1 R0/ Local R2

6.2. Failure pressure based on 3 parameter fracture criteria In this section, fracture-based failures pressure of Ø3.2m cylindrical shell with long seam weld and Cirseam weld is worked for 5x2mm defect. The unflawed burst pressure estimated from previous section is used to find the failure pressure in presence of 5x2mm defect using the 3 parameter fracture criteria explained before. Table 10 shows the comparison of failure pressure for different cases.