The morphology of cracks in rails

Following the Hatfield derailment in 2000, in which four people died, the Health and Safety Executive funded a project to investigate some of the factors affecting rolling contact fatigue. This paper presents the results of part of that project, looking at the morphology of the cracks present in a section of head hardened rail taken out of service from the Hatfield site. The position of the cracks within the rail head was found by grinding successive layers from the rail starting at the gauge corner, and recording the cracks showing in each level. A three-dimensional computer model was created from the data obtained to aid visualisation. The correlation between the visible surface crack length and crack depth within the rail was also investigated. It was found that generally, a visible crack length of greater than 20 mm corresponded to a crack depth of more than 5 mm. However, a significant number of deep cracks were found to have surface lengths of less than 20 mm.