Local buckling failure analysis of pipelines containing a dent-corrosion defect under combined internal pressure and bending moment

Abstract

In this work, a nonlinear finite element (FE) model was developed to examine the local buckling failure of X80 steel large-diameter pipelines containing a dent-corrosion defect under combined internal pressure and bending moment. The developed model captured the local physical conditions at the defect zone and investigated the influences of buckling failure process, critical bending moment, and plastic deformation propagation. Critical parameters, including corrosion geometries, pipeline dimensions, dent depth, and internal pressure, were evaluated for their effects on the critical buckling moment. The results revealed that the critical buckling moment positively correlates with pipe diameter, wall thickness, corrosion length, and corrosion depth while negatively correlating with dent depth and internal pressure. When the corrosion depth-to-thickness ratio $d/t>0.3$, the buckling moment reduces by over 50 %. Shallow dents ($\le 4\%D$) induce significant stress concentration, while deeper dents ($\ge 6\%D$) enhance buckling resistance due to strain hardening. Among the factors studied, pipe diameter and wall thickness influence buckling capacity most, whereas internal pressure has a slight effect. Corrosion is the primary factor contributing to the buckling failure of a pipeline with a dent-corrosion defect.