PSI - Issue 61

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

319

Gavriilidis et al. / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 2: Deformation sequence of a) Plate during JCO manufacturing process prior to welding, b) JCO pipe under the finishing press, c) expansion phase, resulting in the final pipe geometry of the JCO-E pipe; von Mises contour plot.

1 . 5%, which falls within the optimum expansion range. Fig. 3a also presents the influence of expansion strain on the cross-sectional ovality of the JCO-E pipe ( O o ), as recommended by DNV-ST-F101 standard. Upon increasing the expansion strain, the residual ovality is significantly reduced and remains almost una ff ected for expansion levels greater than 1 . 7%. Furthermore, an imperfection parameter denoted as ∆ T = ( t max − t min ) / t ave is introduced expressing the variation of wall thickness around the circumference of the JCO-E pipe. The measurements are performed at every 30-degrees in the pipe circumference (12 locations) and the maximum ( t max ), the minimum ( t min ) and the average ( t ave ) wall thickness values are obtained. Fig. 3b shows that the ∆ T parameter increases with increasing the expansion level, indicating that the wall thickness decreases after expansion, due to Poisson’s ratio, while similar observations are reported by Chatzopoulou et al. (2016) and Antoniou et al. (2019). The collapse pressure obtained by the two-dimensional finite element JCO-E model is also compared with the numerical results of a three-dimensional model presented by Gavriilidis et al. (2024). The collapse pressure predicted by the three-dimensional model is 38 . 5 MPa, using stress-strain material curves obtained from coupons extracted from as-fabricated JCO-E line pipe, while the collapse pressure of the present numerical model is 37 . 5 MPa, considering