Fracture mechanics assessment of railway axles: Experimental characterization and computation

The results of a joint research project aiming at developing validated fracture mechanics assessment procedures for railway axles are presented. Experimentally determined fatigue crack growth parameters for the commonly used axle steel 25CrMo4 (A4T) and the high strength steel 34CrNiMo6 are included in the range of stable crack propagation and near threshold. The results are employed for predicting fatigue crack growth for cracks initiating at the axle shaft. For the computational modelling of fatigue crack propagation a generally applicable solution for stress intensity factors has been derived. Furthermore, the influence of variable amplitude loading (block loading) on the crack propagation behaviour has been studied and is discussed. The computational results are in good agreement with experimental data determined on standard fracture mechanics specimens as well as down-scaled and geometrically similar axle specimens.