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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The reduced collapse pressure capacity of those cold-formed pipes is mainly related to the last step of the manufac turing process, where the pipe is expanded to minimize the cross-sectional ovalization, and thus an important amount of tensile plastic deformation is stored in the material. This extensive tensile deformation is important in deep-o ff shore environments where the pipe material will be subjected to compressive loads, and therefore the Bauschinger e ff ect will appear. However, Kyriakides et al. (1991) and Reichel et al. (2011) proposed a modified cold-forming process by replacing the expansion step with uniform comppression, in order to eliminate the Bauschinger e ff ect. Previous works have converged that the compressive strength of pipe material is a key factor that a ff ects the structural integrity of pipelines under external pressure loading conditions, and thus it is of major concern in o ff shore applications. The present paper describes a finite element methodology for simulating the JCO-E manufacturing process and the response of the final product under external pressure. The procedure is applied on a a thick-walled 30-inch-diameter line pipe which is simulated using a two-dimensional (2D) finite element model, considering a steel plate with thick ness equal to 39 mm and forming parameter information, which are provided by the pipe mill. At the end of the process the finite element model is validated with measurements made on the actual 30-inch-diameter pipe. Upon completing the simulation of the manufacturing process, the pipe is subjected to uniform external pressurization, which leads to the numerical prediction of the collapse pressure. The parameters associated with the process are investigated though parametric studies and the results have shown that an optimum expansion range exist for producing a pipe with minimum geometric imperfections and ultimate collapse resistance. Finally, the collapse pressure estimation obtained from the two-dimensional manufacturing model is compared with a three-dimensional model (Gavriilidis et al., 2024), which simulates the full-scale collapse of the same pipe.

Nomenclature

C E mid-surface length of the pipe circumference at the end of the expansion phase C W mid-surface length of the pipe circumference at the end of the JCO phase D pipe outer diameter E Young’s modulus P external pressure P co collapse pressure P y yield pressure t pipe wall thickness

t ave average wall thickness t max maximum wall thickness t min minimum wall thickness O o residual cross-sectional ovality ∆ T wall thickness parameter ε E expansion strain ν Poisson’s ratio σ y yield stress

2. Numerical modelling

2.1. Description of the JCO-E finite element model

The general-purpose finite element program ABAQUS / Standard (2016) is used for creating a quasi two dimensional (2D) model that simulates the JCO-E manufacturing process and the response of the final line pipe under external pressure. The kinematic and geometric parameters associated with the manufacturing process of the 30-inch-diameter pipe with D / t equal to 19 . 69 have been provided by Corinth Pipeworks S.A. (CPW). Those geo metric parameters correspond to the actual dimensions of the plate, the forming dies, the punch and the expander