A Three-Dimensional Coupled Finite Element Model for the Simulation of Stress Corrosion on Pipeline Steel

Abstract In this study, a three-dimensional finite element model was constructed to study the stress corrosion behavior of pipeline steel. Stress analysis and electrochemical calculation were incorporated into the model through multiphysics field coupling technique. Tensile property and electrochemical corrosion behavior of X70 pipeline steel were measured by experiments to formulate the model. The modeling results show that the corrosion is accelerated on the surface of corrosion defect where the stress tends to concentrate because of mechanoelectrochemical effect. The effect of elastic strain on corrosion enhancement is not obvious. The plastic deformation on defect bottom increases the corrosion rate significantly, especially for the conditions with high operating pressure or large defect depth. The corrosion current distribution indicated that the “self-acceleration effect” exists on corrosion defect. This effect makes the corrosion develop to depth and the shape of corrosion defects is more likely to cause stress concentration, and finally induces corrosion perforation or cracking. The two directions, i.e. axial and circumferential direction, have the different stress corrosion behaviors. The “self-acceleration effect” is more obvious on circumferential direction than that on axial direction, which can explain the phenomenon that there are mostly axial stress corrosion cracks on the pipeline in field.