PSI - Issue 60

Rohan Nair et al. / Procedia Structural Integrity 60 (2024) 93–114 Rohan Nair / Structural Integrity Procedia 00 (2023) 000–000

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4.6.

Fractographic analysis of burst tested test article:

Thickness at fracture edge was measured using FESEM and it varies from 600-1100um. Thickness at location L1 is 600-700um which is the thinnest location. Based on the combination of minimum failure edge thickness, maximum separation gap in the failure region, coupled with observation of maximum strain (from the strain gauge data), it can be confirmed that L1 location is the fracture initiation point. Fractographs of samples extracted at different location are shown in Fig. 29 and all samples showed ductile dimple features confirming the mode of failure by over load. Location C1 is the circumferential weld through which the fast fracture has occurred as can be clearly seen in the Fig. 29 (a), which shows multiple fine pores with dendritic features within them (shown with yellow arrow).

Fig. 29: Fractographic images of burst tested AA 6061 water tank a) at location C1, b) at location L1, c) at location L2, and d) at location L3

5. Conclusions: Test article of AA6061 material was successfully realized and pressure tested to assess its load bearing capability. The test results validate the manufacturing processes and toolings adopted to realize the PS2 water tank. The strain recorded during the proof pressure and burst test were as per the predicted values confirming the analysis. The microstructural observations of the welds did not reveal any defects, except microscopic porosity and fractographic examination of the bust tested hardware showed ductile mode of failure. Based on these results, the water tank realisation process has been cleared for production of flight worthy water tank.