Characterization of crack initiation and propagation in anisotropic material (CHARMEC MU35)

Research Project, 2019 – 2024

An anisotropic and aligned microstructure is found in the surface layer of pearlitic railway rails and wheels, formed in operation by rolling contact fatigue (RCF) loading. The direction of the aligned microstructure is not well suited to resist crack propagation into the rails and wheels. The shapes of typical head checks and RCF cracks are a result of the anisotropy in toughness, and the depth of the anisotropic layer varies with steel grade. The aim of the present project is to gain a better understanding of the anisotropy developing in wheel and rail surfaces during service operation. Fatigue crack initiation and propagation experiments in anisotropic microstructures will lead to a better understanding about crack paths and to an improved background for modelling work, and also to improved prediction of safety limits and maintenance actions. Samples from field will be characterized for comparison, and interaction with Shift2Rail demonstrators is foreseen. Attempts to create a more favourable anisotropy are included.

This is a doctoral project. Mr Daniel Gren is the doctoral student and Professor Johan Ahlström the project leader and supervisor. Professor Magnus Ekh is assistant supervisor and Professor Christer Persson is examiner.