PSI - Issue 61

Ilias Gavriilidis et al. / Procedia Structural Integrity 61 (2024) 315–321 Gavriilidis et al. / Structural Integrity Procedia 00 (2024) 000–000

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6

P co /P y

O o

(a)

(b)

Fig. 3: Variation of a) normalized collapse pressure ( P co ) and residual ovalization ( O o ) with respect to expansion strain ( ε E ), and b) thickness parameter ( ∆ T ) with respect to expansion strain ( ε E ).

the expansion level used in the pipe mill ( ε E = 1 . 3%). Gavriilidis et al. (2024) also presented the e ff ect of mild heat treatment on the compressive strength of the pipe material and the collapse pressure. The mild heat treatment corresponds to a typical coating process of a line pipe and was validated with full-scale experimental collapse tests.

4. Conclusions

A two-dimensional finite element model, which is capable of simulating the JCO-E manufacturing process and predicting its ultimate resistance under external pressurization, is created in the present work, and it is validated with actual geometric measurements provided by the pipe mill. The e ff ect of the expansion step on the geometric properties and the collapse performance of the JCO-E pipe is investigated. Several expansion strains are considered, showing that an optimum range of expansion exists between 0 . 7%and1 . 8%, while the maximum collapse pressure ( P co = 37 . 7 MPa) is observed at 1 . 8% expansion strain ε E . Increasing further the expansion strain results in reducing the collapse pressure, an observation attributed to the Bauschinger e ff ect. Additionally, for expansion strain values up to 1 . 7% the expansion is beneficial for the cross-sectional geometry by reducing the residual ovalization, while for expansion strain values greater than 1 . 7%, the residual ovality remains almost constant at 0 . 07%. Furthermore, the pipe wall thickness decreases with increasing the expansion strain in the range of ε E under consideration, due to Poisson’s ratio. Finally, the collapse pressure calculated from the two-dimensional finite element JCO-E model is in good agreement with the collapse pressure of a three-dimensional model, calibrated with material curves from an as-fabricated JCO-E pipe, that simulates the full-scale collapse test.

Acknowledgements

The research work in the present paper was supported by a financial grant from the Hellenic Foundation for Research & Innovation, Project No. 7041, entitled “Structural Integrity of O ff shore Energy Platforms”, project acronym: SIRENES (2022-2025). The authors would like to thank Corinth Pipeworks S.A., Thisvi, Greece, for their close cooperation throughout this research.