PSI - Issue 60

Varsha Florist et al. / Procedia Structural Integrity 60 (2024) 614–630 629 16 Varsha Florist, Santhoshkumar R, A. Vamsi, Sajju V, Sarath Mohan, Sanjeev Kumar, Dhanoop A, Venukuttan C, M.K. Sundaresan, SVS Narayana Murty / Structural Integrity Procedia 00 (2024) 000 – 000

a)

b)

Ductile dimples

10 µm

50 µm

c)

d)

Brittle Cleavage

50µm

10 µm

Fig. 20. FESEM images of fracture surface indicating plastic deformation with mode of failure along (a-b) circumferential fracture edge; (c d)longitudinal fracture edge Examination of the weld zone which was extracted from circumferential fracture surface near weld location showed dendritic type structure throughout the weld and did not reveal cracks, porosities, lack of penetration or lack of fusion which confirm the soundness of weld. Fig. 19 shows the fractographs recorded from the tensile test specimens of parent material and weld, respectively, which reveals mixed mode of mode of failure. Fig. 20 shows the fractographs obtained from FESEM of both circumferential and longitudinal fracture edge of the tank revealing the mixed mode of failure. Cleavage like failure with ductile dimple features are observed on the fracture surface indicating plastic deformation along the longitudinal edge of burst tested tank V. Diwakar (1985), T Christopher (2004). 6. Conclusion • Based on the compatibility with the storing medium, high strength, and simple heat treatment, 15-5PH stainless steel is selected for the realization of tank with revised proof and ultimate factors of 1.25 and 1.5. • Design of 15-5 PH tank in flow formed route with reduced number of welds has also been carried out. Ultimate load factor of 4.0 is ensured during pre-pressurization phase of the tank. • FE analysis on the cylindrical shell with thick ring, fore end dome and aft end dome has been carried out and stresses are found within acceptable limits. • The pressure vessel has been redesigned with cylindrical shell thickness as 4.2mm (4.5 mm at weld) and for the dome, thickness varies from 3.5mm to 6mm. • Cylindrical shell of the tank was realized through a novel technique of flow forming, thereby reducing the number of welded joints and associated non-destructive testing. • The tank has been subjected to extensive qualification tests, including burst test and results were satisfactory. Also, sufficient numbers of mechanical tests have been performed on preforms, first article inspection and production batches of flow formed shells.