Assessment of stress intensity factors for cast iron pipes with pitting corrosion

Accurate prediction of structural response of buried metal pipes relies upon the surrounding soil condition as well as pipe wall thickness deterioration. The presence of localized pitting corrosion, which is induced due to the electro-chemical reaction between soil and iron, has been identified as one of the main deterioration mechanism of pipe wall thickness. These corroded pipes, when exposed to severe loadings, can be easily subjected to failures in the forms of either rupture or bursting due to intensified stresses at the flaws. The assessment of such intensified stresses has been a key focus since recently due to high significance associated with the prediction of pipe failures. Although the stress intensity factors for pipe with surface (2D) crack has been studied in literature, there is no study essentially relating the stress intensity factors of pipes with the geometry of pitting corrosion. In present study, a 3D geometry model of pitting corrosion is proposed and a three dimensional finite element method is employed to derive the solutions of stress intensity factor for pitting corrosion with various geometric properties. This research provides a fundamental support for safety evaluation and life prediction of buried cast iron pipelines