Fatigue life enhancement of foreign object impacted railway axle EA4T steel with surface shot peening

Abstract

This study investigates the effects of surface reinforcement and foreign object damage (FOD) on the fatigue property of the EA4T alloy steel used for high-speed railway axles. The results of characterization of its microstructure revealed the evolution of the shot-peening-reinforced layers and the craters induced by the impact. Moreover, the results of reconstruction of the residual stress field at the crater, obtained by combining the Johnson–Cook model with the temperature field difference setting method, showed the development of residual tensile stress at the rim of the impact crater and residual compressive stress at its bottom. The fatigue test results demonstrated that surface reinforcing can effectively enhance the fatigue resistance of FOD induced specimens. Probabilistic fatigue SN curves constructed by an improved backward statistical inference method can be used to derive reliable fatigue properties. The fatigue-induced fracture showed that the combination of competing effects of stress concentration, residual stress, micro damage and microstructure were the main fatigue failure mechanisms of axles subject to foreign object damage. The curves of the crack growth rate predicted by the iLAPS model indicated that the service life of the damaged axle can be adequately calculated based on its static tensile properties.