Finite element analysis of UOE manufacturing process and its effect on mechanical behavior of offshore pipes

Abstract

• We simulate the UOE forming process, using finite elements and an advanced plasticity model. • We present results for geometrical imperfections and anisotropy induced by the UOE forming process. • We investigate the effect of cold-forming on the performance of UOE pipes under external pressure, tension and bending. • We compare the structural performance of UOE pipes with the performance of seamless pipes. • We examine the efficiency of a simplified methodology for determining the structural capacity of a UOE pipe. Thick-walled steel pipes during their installation in deep-water are subjected to a combination of loading in terms of external pressure, bending and axial tension, which may trigger structural instability due to excessive pipe ovalization. The resistance of offshore pipes against this instability depends on imperfections and residual stresses due to the line pipe manufacturing process. The present study examines the effect of UOE line pipe manufacturing process on the structural response and resistance of offshore pipes during the installation process using advanced finite element simulation tools. The cold bending induced by the UOE process is simulated rigorously and, subsequently, the application of external pressure and structural loading (bending or axial force) is modeled, until structural instability is reached. A parametric analysis is conducted, focusing on the effects of line pipe expansion on the structural capacity of the pipe. The results show that there exists an optimum expansion at which the highest pressure capacity is achieved. The effect of the axial tension on the pressure capacity of the pipe is examined as well. The influence of the line pipe expansion on bending capacity in the presence of external pressure is also identified. Finally, a simplified methodology is employed, accounting for the material anisotropy induced by the manufacturing process, capable of determining the structural capacity of a UOE pipe in a simple and efficient manner with good accuracy, using more conventional modeling tools.