Experimental and numerical study on press-fitted railway axles: Fretting fatigue behaviour in the very high cycle regime

Fretting fatigue cracks at the press-fitted part of railway axles are commonly observed in the very high cycle (VHC) regime. However, most studies concerning the fretting fatigue behaviour of railway axles have been limited to the high cycle (HC) regime, which cannot provide sufficient knowledge to ensure the safe operation of railway axles over a service life of 30 years. In this study, fretting fatigue experiments for scaled railway axles were extended from the HC regime to the VHC regime. The fretting wear and fretting fatigue damage were observed and measured. Finally, based on the finite element simulation, an evaluation method coupled with the Modified Wo center dot hler Curve Method (MWCM) and the theory of critical distance (TCD) was developed to investigate the fretting fatigue damage. The experimental investigation found that the fretting fatigue strength of railway axles in the VHC regime decreased with an increase in the number of test cycles, which can be described by the Basquin equation. This suggests that the fretting fatigue strength in the VHC regime can be predicted to provide data for the design of safer railway axles. The numerical study showed that the developed evaluation method can provide a reasonable estimation of the occurrence of fretting crack initiation in the VHC regime, and that the fretting fatigue damage can be described by the MWCM equivalent stress. The stress concentration at the press -fitted part gradually increased due to the continuous fretting wear, which resulted in the disappearance of the fretting fatigue limit of the press-fitted railway axles in the HC regime, and VHC fretting fatigue occurred.