Allowable wheel loads, crack sizes and inspection intervals to prevent rail breaks

Paper in proceeding, 2015

Cost-efficient and reliable heavy haul operation requires a minimum of operational disturbances. To this end, the current study focuses on wheel load management with the aim to establish wheel load monitoring and mitigation actions (in terms of limits on allowable wheel defects) that minimize traffic disruptions. As a first step, the relation between wheel impact load magnitudes (resulting from the out-of-round wheels) and critical rail crack sizes that would result in rail breaks is established. Variations in parameters such as track stiffness, rail temperature, impact load characteristics and hanging sleepers etc. are investigated and a “bad case scenario” that implies severe, but realistic operational conditions is established. In this manner allowable wheel impact load magnitudes can be linked to pertinent critical crack sizes that must be identified during inspections. An interesting finding is that thermal stresses have such a major effect that a seasonal variation in allowable wheel load limit seems justified. Predicted critical crack sizes (presuming allowed wheel load magnitudes) are then contrasted to critical crack sizes at operational rail breaks. A large scatter in operational critical crack sizes is found and reasons for this fact are discussed. Finally operational aspects of implementing the suggested limit values are discussed.