Contact defects initiation in railroad wheels – Experience, experiments and modelling

Main results of comprehensive research of rolling contact defects initiation are presented in this contribution. Description of own experimental study has been preceded by practical experience of a wheelset producer. A line rolling/sliding contact case with creepage of 0.75% was investigated using a unique test machine. The rail disc was made from Class C steel grade while the wheel disc from R7T steel grade. Unlike the standard twin-disc test, the diameter of the rail disc was 2.6 times bigger than the diameter of the wheel disc. Development of contact cracks and accumulation of shear strain for the wheel material R7T during rolling contact loading were namely evaluated. On the basis of test conditions, simulation by FEM was performed. As the result, very good prediction of shear strain accumulation was achieved using the AbdelKarim–Ohno cyclic plasticity model. The proposed computational strategy can be used for fatigue life prediction till initiation of a crack caused by low-cycle fatigue or by ratcheting failure.