Residual Stress Characterization in Railway Axles: A Key Step for Reliable Fatigue Crack Growth Assessment

Accurate residual-stress assessment is essential for reliable fatigue-life prediction of railway axles, because residual stresses form a major part of the effective loading state together with service loads and press-fit stresses. This contribution focuses on induction-hardened railway axles, where surface treatment can generate high compressive residual stresses and a steep stress gradient through the cross-section. Compressive axial residual stress near the axle surface may reduce the effective crack-opening driving force, promote crack closure, and retard the growth of fatigue cracks initiated from ballast impacts or other surface defects. As a result, the residual fatigue lifetime of the axle can be substantially increased.

The work presents a methodology for determining residual stresses across the full axle cross-section by combining destructive specimen preparation, X-ray diffraction measurements, and finite-element correction of stress redistribution. Approach, based on layer removal and sectioning, is applied to an induction-hardened hollow axle. The results show compressive axial residual stresses of approximately -600 MPa up to 8 mm below the surface, followed by tensile stresses deeper in the axle. These findings demonstrate that precise residual-stress characterization is necessary for damage-tolerance assessment and optimization of axle surface treatment.