Finite element modeling of the JCO-E line pipe fabrication process; material properties and collapse pressure prediction

Abstract

A numerical method for the simulation of the JCO-E pipe fabrication process is presented. The deformation and stresses induced by the manufacturing process, namely the edge crimping, the JCO forming, the LSAW welding, and the expansion (E) operation are calculated utilizing finite element simulation tools. This paper continues a recent work of the authors; it enhances the material model to account for the plate anisotropy, through the development of an in-house material subroutine, and simulates more accurately the welding process. Considering the fabrication parameters of the pipe mill, an X65 line pipe with 26-inch nominal diameter and 0.75-inch nominal thickness is simulated numerically with finite elements. The level of anisotropy is introduced in the model using stress–strain curves obtained from strip specimens, extracted from the steel plate. The predicted material properties of the JCO-E pipe are compared with test results from strip specimens extracted from the produced line pipe. Following the simulation of the fabrication process, and using the same finite element model, the analysis continues so that the mechanical response of the 26-inch-diameter pipe under external pressure is obtained, and its collapse pressure is calculated for different values of the applied expansion. The numerical results show that expansion reduces ovalization and residual stresses in the pipe, and there is an optimum range of expansion strain corresponding to maximum collapse pressure of the JCO-E pipe; beyond that range, the collapse pressure is reduced because of the Bauschinger effect.