Abstract
For small to medium size rigid pipelines, reel-laying is an efficient installation method. Higher lay rates are achieved thanks to unreeling rigid pipeline down to seabed. However, the process is mechanically onerous. Pipelines go through successive large bending strains up to 2% or 3%. This is the primary degradation mechanism and affects the mechanical in-service performance of the subsea line. Assessment of material response to the installation sequence is a key point for pipeline engineering. Conventional monotonic material stress-strain relation or cyclic Ramberg-Osgood models are not suitable for repeated large bending sequences or reel-lay installation FE simulations. A parameter-based material model has been tailored for carbon steel seamless pipe under reeling. The evolution of the material behaviour from the first load to stabilised cycle is addressed, by introducing an Abaqus User Subroutine written in FORTRAN. The material properties are programmed in each straining cycle, then active in their corresponding loading cycle. Specimens from DNV450 grades pipe have been tested in an extensive small-scale test and bending trial campaign in order to calibrate finite element model. DIC is used during tensile test and LCF (Low Cycle Fatigue) test to allow accurate measurement on large straining ranges. The parameter-based model can provide response to the first load, including Lüders plateau, up to stabilized hysteresis loop; it is fully parametric by Python. Comparison is made with the more conventional material model or full-scale bending trials demonstrating improved accuracy and agreement with testing. The proposed material model is part of an in-house material model library integrated in a numerical tool package dedicated to rigid pipeline design.
