An investigation on the influence of rotary bending and press fitting on stress intensity factors and fatigue crack growth in railway axles

The present paper summarizes the results of fatigue crack growth investigations on a hollow railway axle which were undertaken as a joint research project between the Politecnico di Milano, Italy, and the GKSS Research Centre Geesthacht, Germany, within an activity of ESIS-TC24 (Technical Committee on the Integrity of Railway Structures). Since no analytical stress intensity factor (SIF) solutions for semi-elliptical surface cracks in the S-transitions of railway axles were available, the first step in the research was to generate them for both reverse and rotary bending. The results were then used to investigate both the effects of rotary bending, and, of the press fits at the wheel and gear, on the fatigue crack growth and residual lifetime so as to provide essential input information for setting up inspection intervals. It was found that the effect of rotary bending, although existent, was rather moderate whereas the press fits had a large and detrimental effect.