Probabilistic fatigue assessment for high-speed railway axles due to foreign object damages

Various surface defects of high-speed railway lightweight hollow axles made of alloy steel were identified carefully for assessing its operation safety and reliability. Three types of foreign object damages (FOD) from compressed-gas gun device were defined as the corner, edge and plane defects in terms of defect geometry, respectively. The fatigue probabilistic S-N (P-S-N) curves and fatigue limits were acquired for smoothed and FOD-affected specimens. In view of the variations of size and roughness between the full-scale axles and specimens, the fatigue properties with three defect types were then modified for full-scale axles. The probabilistic Kitagawa-Takahashi diagram widely used for assessing the FOD in aero-engine was well transferred to the damaged railway axles. The fatigue limits of an FOD-affected axle with 95% confidence level and 95% reliability level were evaluated to replace that of smoothed specimens, which was suggested to assess the reliability of a damaged axle at the presence of FOD generated at a prospective higher operation speed.