Effect of large shear deformation on fatigue crack behavior in pearlitic rail steel
Licentiate thesis, 2022

The impacts from global warming and climate change continue to rise and securing the needs of future generations requires a transition to a climate-neutral society. Rail transportation, as being one of the safest and most energy efficient modes of transportation offers a sustainable alternative to fossil-fueled based transportation. There are however many challenges that must be addressed for rail transportation to be a viable option. Safety, functionality, reliability and economic feasibility must be ensured. The major challenge related to materials is rolling contact fatigue which impairs the safety and economic reliability. The key factor to mitigate the effect of rolling contact fatigue is to understand how the material behavior changes when the material is subjected to repeated rolling contact loading. The imposed loadings from the wheel/rail contact induces severe deformations in the near-surface region of the rail and leads to the formation of an aligned and anisotropic microstructure. Rolling contact fatigue cracks is often initiated in this
region and crack propagation is promoted by the direction of the microstructure alignment. The shape of typical head checks for example, correlates well with the anisotropy infracture toughness.

The aim of this thesis work is to better understand how the anisotropy developing in service changes the fracture and fatigue characteristics of rail steels. Fatigue crack growth experiments under uniaxial and pulsating torsional loading, on both undeformed and predeformed pearlitic rail steel R260 have been conducted. The material state of the predeformed material is similar to the material state in the near surface of deformed rails and was obtained by large shear deformation under compression. The fatigue crack propagation experiments showed that the fatigue life is dependent on the material state
where predeformed material have longer fatigue life. The effect of predeformation on the crack growth direction was limited in uniaxial loading whilst dependent on the material state in torsional loading.

Pearlitic steel


Torsional loading

Fatigue crack propagation

Uniaxial loading


Virtual Development Laboratory, Chalmers Tvärgata 4C
Opponent: Prof. Jens Bergström, Karlstad University


Daniel Gren

Chalmers, Industrial and Materials Science, Engineering Materials

Daniel Gren, Johan Ahlström, Fatigue crack propagation on uniaxial loading of biaxially pre-deformed pearlitic rail steel

Daniel Gren, Knut Andreas Meyer, Effects of predeformation on torsional fatigue in R260 rail steel

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

European Commission (EC) (EC/H2020/730848), 2019-06-10 -- 2024-06-09.

Chalmers Railway Mechanics (CHARMEC) (MU35), 2019-06-10 -- 2024-06-09.

Subject Categories

Materials Engineering

Metallurgy and Metallic Materials

Areas of Advance

Materials Science

Thesis for the degree of licentiate of engineering / Department of Materials Science and Engineering, Chalmers University of Technology: IMS-2022-8



Virtual Development Laboratory, Chalmers Tvärgata 4C

Opponent: Prof. Jens Bergström, Karlstad University

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