Rail web fracture in the presence of residual stresses

A recent accident involving roller-straighened alloy rail has raised the question of the safety of such rails. This work shows that the residual stresses in roller-straightened rail can indeed self-drive a long web crack. Specifically, the stress intensity K_I due to release of the key component, longitudinal stress, if of the order of the critical stress intensity for initiation K_Ic for both plain carbon and alloy rail. At cut ends, the resulting vertical residual stresses can give rise to K_Ic if there are 0.1–1 in (3–25 mm) cracks. In this work, checks of the existing residual stress data for self-consistency suggest that the data are only accurate within a factor of two. Therefore, a more direct method is proposed for measuring K_I on a web crack by saw-cutting the web.