Estimation and consequences of the crack thickness parameter in the assessment of crack growth behaviour of “squat” type cracks in the rail–wheel contact zone

The paper presents the results obtained from investigations of the “squat” type crack serving as an example of the rolling contact fatigue crack that appears in rail heads. Some geometrical parameters of the crack can be defined. The work is devoted mainly to the problem of crack thickness, i.e. the gap between crack faces. The observation of crack faces allowed us to formulate a concept of how this gap is forming. The crack thickness distribution over the whole crack face was measured. The results obtained were introduced into 3D FEM models. The paper also describes the changes in crack thickness distribution in the course of wheel rolling over the crack and the resulting crack volume changes.