Kalle Karttunen

A numerical study of the influence of lateral geometry irregularities on mechanical deterioration of freight tracks

Optimisation of railway track maintenance requires knowledge of how a deteriorated track geometry will affect subsequent loading and damage of the track. This is the scope of the current study where, in particular, the influence on track shift forces and rolling contact fatigue is investigated through numerical simulations. To this end, track geometries are obtained from field measurements. Lateral irregularities are extracted and scaled to represent different levels of geometry deterioration. Multibody simulations of dynamic train–track interaction featuring two freight wagon types are performed under different operational conditions. Track shift forces and rolling contact fatigue damage are further evaluated from simulation results. It is found that track shift forces tend to follow a normal distribution for moderate levels of lateral track geometry irregularities, and that an approximate linear relationship between standard deviations of lateral irregularities and track shift forces can be established. The relation between lateral track irregularity magnitude and rolling contact fatigue is more complex. Increasing levels of lateral irregularities will decrease the fraction of curve length affected by rolling contact fatigue for sharp curves, whereas for shallow curves it increases. As detailed in the article, this is caused by the lateral movement of the contact point as imposed by the track irregularities. Furthermore, the influence of wheel/rail friction and wear is investigated.

Identifying the root causes of damage on the wheels of heavy haul locomotives and its mitigation

The paper illustrates how damage patterns in the form of rolling contact fatigue (RCF) on wheels, can be employed to identify and improve underlying operational conditions. The focus is on RCF of locomotive wheels operating on the Iron Ore Line in northern Sweden and Norway. Seasonal changes and damage patterns are charted. Potential root causes for observed damage patterns are identified and investigated. Mitigating actions are proposed and the efficiency of implemented actions is quantified.