Experimental validation of a model for predicting the bending fatigue strength of corroded grey cast iron water pipes

Leakage of drinking water caused by mechanical failures of old, buried, Grey Cast Iron (GCI) water pipes is a serious issue for water utilities in the UK and around the world. To enable better-informed pipe health assessments to be made, this work aimed to experimentally validate a method that could be used to assess the damaging effect of corrosion pitting on GCI pipes subject to bending fatigue loading. Fatigue testing of GCI pipes revealed pitting had a small detrimental effect on the pipes’ bending fatigue strength, characterised by Kt = 1.38 for the sharp pit specimens. An effective volume approach coupled with the SWT multiaxial fatigue criterion was found to provide reasonable fatigue life predictions, at the expense of requiring the 3D geometry of the pit to be known. Making predictions simply using the net stresses provided conservative predictions, but only required the pit’s depth.