Material characteristics in welding and other local heating events (CHARMEC MU36)

Research Project, 2019 – 2024

Welding and grinding processes induce local heating that can deteriorate the properties of the base material. In welding the situation can be improved by introducing fillers to modify the steel chemistry and by controlling heat supply to create beneficial heat treatments. Short term local friction heating in the wheel-rail contact is another scenario causing similar temperature elevations. If the temperature rises above ca 800 °C in rail and wheel steels phase transformations take place. These result in residual stresses and localisation of strains upon subsequent rolling contact loading, which can cause crack initiation in rail and wheel surfaces. Also lower peak temperatures can lead to residual stress fields and changed strength. Project MU36 aims at expanding the knowledge of material behaviour under combined thermal and mechanical loadings. Accurate prediction of the resulting gradients in mechanical properties and residual stress is crucial for a proper judgement of rolling contact fatigue damage accumulation in railway operations. The present project will build on previous experimental works and, in co-operation with project MU37, lead to accurate and predictive methods supporting technology development and decreasing LCC.

This is a doctoral project. Ms Erika Steyn is the doctoral student and Professor Johan Ahlström the project leader and supervisor. Professor Magnus Ekh is assistant supervisor.