Fatigue performance evaluation of high-strength railway axles subjected to different surface defects

Defects are the root causes of fatigue failure of railway axles. The purpose of present paper is to evaluate the fatigue behavior of high-strength 30NiCrMoV12 railway axle subjected to different surface defects, including electric discharging machine (EDM) notch, quasi-static indentation and impact damage. Balls and cubes made of bearing steel were shot by a compressed-gas gun toward specimens to create impact damages. Rotate-bending fatigue tests were conducted and morphologies of defects and fracture surfaces were characterized to correlate degradation of fatigue strength with defect geometry. The results show that the indentation and impact damage by ball imposes little influence on the fatigue strength, while the EDM defect is significantly detrimental. The shape variety of impact damage generated by flying cubes led to a larger scatter in fatigue behavior. A conservative estimation could be obtained by regarding the impact damage as EDM defect with equivalent depth.