Effect of material strength on shelling property of railway wheel steel

Shelling is the typical rolling contact fatigue (RCF) failure of the railway wheels. In order to evaluate effect of the material strength on the shelling properties of railway wheel steels, RCF tests and FE analyses were conducted. The RCF tests were carried out in the twin disc type testing machine. Wheel specimens made of two kinds of wheel steels with different strength were tested under water lubrications in the RCF tests. The elasto-plastic FE analyses were carried out to calculate the stress intensity factors (SIF) of the surface cracks in the RCF tests. The water penetrations into the surface cracks were taken into consideration in FE analyses. There are two main results in this study. Firstly, the RCF test results showed that the RCF strength of the higher strength wheel steel increased comparing with that of the lower strength wheel steel. Secondly, the SIFs of the branched cracks of the higher strength steel reduced as a result of being the shallower crack depth by decrease of the hydrostatic pressure in the cracks. In addition, these SIFs at the fatigue limits in the RCF tests corresponded to the threshold ranges of the SIF ΔKth of each material. Therefore, these results suggest that the fatigue limits in the RCF tests are influenced by the maximum crack depth. © 2012 The Society of Materials Science, Japan.