Relatore
Descrizione
Most freight trains use a pneumatic braking system that does not ensure synchronised
braking between different wagons. This lack of synchronisation results in significant in-train
forces during emergency braking, which is sometimes triggered by the railway
infrastructure when certain speed thresholds are exceeded. The magnitude of these forces
depends on several factors, including train length, mass, load distribution and the specific
braking operation being performed, e.g. after acceleration or from coasting conditions.
Excessive compressive in-train forces can lead to wagon derailment, particularly when
light wagons are travelling through curves with small radii. Conversely, excessive tensile
forces can compromise the integrity of the coupling system, leading to premature fatigue
failures, interrupting train service and requiring the recovery of separated train sections. In
the light of the above framework, and to increase the applicability of the results, this study
carries out an investigation of the fatigue behaviour for the International Union of Railways
(UIC) unified coupling system, using load spectra generated by the UIC TrainDy software.
The calculated trains are statistically generated and have the same mass and length in
order to provide a significant variability for the load spectra used by the finite element
analysis. The aim is to develop a maintenance model that is capable of predicting the
extent of damage to the screw couplings of freight wagons during their service life. Based
on a systematic and automated analysis of realistic load cycles, the model will allow the
optimisation of maintenance strategies and, at the same time, the improvement of railway
efficiency.
