Härtill 5 uppsatser

Diss. (sammanfattning) Göteborg : Chalmers tekniska högskola, 2024

The impacts from global warming and climate change continue to rise, and securingthe needs of future generations requires a transition to a climate-neutral society. Rail transportation, as one of the safest and most energy-efficient modes of transportation, offers a sustainable alternative to fossil-fuel-based transportation. There are, however, many challenges that must be addressed for rail transportation to be a more competitive option. Safety, functionality, reliability, and economic feasibility must be ensured. The major challenge related to materials is rolling contact fatigue, which impairs safety and economic reliability. The imposed loadings from the wheel/rail contact induce severedeformations in the near-surface region of the rail, leading to the formation of an aligned and anisotropic microstructure. Rolling contact fatigue cracks are often initiated in this region, and crack propagation is affected by the direction of the microstructure alignment. The aim of this thesis work is to better understand how the anisotropy developing inservice changes the fatigue and fracture characteristics of rail steels. Fatigue crack propagation experiments under uniaxial, pulsating torsional, and non-proportional multiaxial loading, on both virgin and predeformed pearlitic rail steel R260 have been conducted. The material state of the predeformed material is similar to the material state in thenear surface of used rails and was obtained by bi-axial large shear deformation undercompression.