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

27

Table 4: increase in failure pressure due to load sharing by parent metal Long seam weld % increase in failure pressure Virgin weld R0 weld 1.1% R1 weld 1.4% R2 weld 1.3% R3 weld 0.9%

4.2. Effect in cirseam weld To simulate the cirseam weld, an axi-symmetric FE model is made. Typical model used for the study is shown in fig 3 below. To simulate this, one end of the model is fixed whereas at the other end equivalent axial load is applied . Uniform internal pressure is applied at inner surface. Other details of solver are same as described in the above section 3.1. The results are summarized in the table 5

Fig 3: Typical FE model simulating the cirseam weld and parent metal properties

4.2.1. Interpretation of FE results of cirseam weld 

In all cases the failure is by net section yielding.  In the conservative model, the failure pressure reduces from 97.37ksc to 79.68 ksc when R2 weld repair properties are considered for full model. i.e. failure pressure reduces by 22.2%.  In the model simulating the weld as well as the parent metal properties, there is no reduction in the failure pressure i.e. at 97.37ksc for different weld conditions.  Here the circumferential (hoop) load is shared by two circumferential areas. One resisting area is having complete parent metal properties and the other resisting area is also having majority of region parent metal property as shown in figure 3 above. Only a very small length is having weld properties i.e. only 3% of overall shell length is weld bead width. Since the reduction in property of resisting area is very small, the failure pressure reduction on account of cirseam weld is negligible. In case of cirseam weld, if conservative model is used the reduction in failure pressure is as high as 26.78% for R3 weld condition. So, while estimating the failure pressure for cirseam weld, it is unrealistic to estimate the failure pressure with full weld properties neglecting the effect of parent metal properties. Since the length of cirseam repair in axial direction is weld bead width (which is always less than 40mm) the failure pressure can be taken as the failure pressure of parent metal itself.