Corrosion Effects on the Strength of Steel Pipes Using FEA

Abstract

This paper presents a finite element investigation on the strength and deformation characteristics of corroded steel pipes with corrosion on the exterior and interior surfaces of the pipes considering different corrosion parameters such as circumferential extent (width) of corrosion, ratio of corrosion width to pipe diameter and the locations of corrosion. The finite element analysis was performed using a commercially available general purpose finite element program, ABAQUS/Explicit. The study reveals that localized bending develops on the pipe wall within the corroded zone that extent up to a certain distance (1 to 1.5 times the corrosion dimension) in the non-corroded area. The localized bending causes stress concentration in the vicinity of the corroded area that is not well captured in the current design standards (i.e. modified ASME B31G). As a result, the modified ASME B31G method overestimated the pipe capacity comparing to the capacity calculated based on the finite element analysis. A pipe designed using the modified ASME B31G method is expected to provide a factor of safety less than the design factor of safety. The effects of circumferential extent of corrosion appears to be less compared to the effects of longitudinal extent of corrosion. The exterior corrosion was found to be more detrimental in comparison with the interior corrosion.