Railway wheel failure caused by flange crack, part 2: Fatigue and fracture assessment

Artikel i vetenskaplig tidskrift, 2026

Causes of a wheel fracture resulting in a derailment that caused major traffic disruptions and costs are investigated based on findings in the first part of this paper [1]. Numerical finite element (FE) simulations together with a fatigue initiation assessment indicate that the fatigue crack at the inside of the flange that triggered the wheel fracture was caused by a combination of wheel–rail contact loads during curving and tensile residual stresses caused by previous overheating of the flange. A fracture mechanics-based analysis is carried out to establish the plausibility of this hypothesis by estimating fatigue crack growth rates and load magnitudes required to cause the final fracture. In order to further assess the influence of flange overheating, the residual stress field is evaluated in a thermomechanical viscoplastic FE-simulation and mapped onto a FE-based fracture mechanics model of the loaded flange crack using an innovative genetic algorithm approach. The study establishes root causes of the fatigue failure to be a combination of high mechanical stresses due to heavy haul operations with worn wheel profiles, and tensile residual stresses caused by prior heating of the flange by a misaligned brake block. Further, scratches on the inside of the flange have acted as crack initiators. Although it is not possibly to evaluate an exact crack growth life due to uncertainties in load magnitudes, the position of crack initiation in relation to the evaluated stress field together with crack growth rate estimations indicate that crack growth started before the previous reprofiling twenty-one months before the derailment.