Fatigue strength and residual life assessment of high-speed railway vehicle used S38C hollow axles

Abstract

The compressive residual stress, basic tensile properties and fracture mechanics parameters of the surface-strengthened carbon steel axle (S38C) have been acquired experimentally and theoretically. The residual stress distribution at the radial direction of the axle was modeled by using the surface unit pressure method through two iterations. Based on measured loading spectrum, the residual life of damaged railway axles was simulated in the framework of fracture mechanics. It is found that the residual compressive stress has a considerable constraint on the fatigue crack propagation or opening. For the fatigue cracks lower than 4.0 mm initiated in the shaft, compressive residual stress still exists at the crack front. Once the crack depth is larger than 7 mm, the crack propagates rapidly. Therefore, the stopping criterion of the S38C axle is suitable with the crack depth 7 mm. Based on classical Paris equation and well-recognized NASGRO equation, the predicted running mileages are 285000 km and 893000 km based on initial crack depth a =4.0 mm, respectively. The applied research method and results provide a significant theoretical reference to determine the fatigue strength and residual life of surface hardened high-speed railway axles with defects.