Keywords: railway dynamics, multibody systems, vehicle-track interaction, wheel-rail contact forces, wheel profile wear.

To improve the competitiveness of the railway transport, trains have to travel faster, with high levels of safety and comfort. As a consequence, railway and infrastructure companies continuously increase the demands for vehicle requirements. These include maintaining the top operational speeds during a trainsets' life cycle, which requires assuring the wheel-rail contact quality. This is a key issue in vehicle design and in train operation since it has a significant impact on the safety and comfort of railway systems and on the maintenance costs of vehicles and infrastructure.

During trainset operation, the wheels of railway vehicles are subjected to wear. When the worn state of the profiles reaches a limit value, the wheels have to be re-profiled. For a better understanding of the wheel wear phenomenon, it is important to tackle two issues: (a) Assessment of the operation conditions that promote the wheel wear growth [1], and; (b) Evaluation of the impact of wheel wear on the dynamic response of trainsets and on their interaction with the infrastructure. The second problem is addressed here. The strategy consists of assembling a vehicle with wheels having new and worn profiles and performing comparative studies in realistic operation scenarios.

The analysis of the wheelsets motion shows that, during curve negotiation, they are displaced laterally towards the outer rail. In the front wheelset in particular, sufficient difference in rolling radii between left and right wheels is not achieved and its lateral shift is only limited by the flange contact. It is also observed that, with both new and worn wheels, the vehicle exhibits a low frequency lateral oscillation with decaying amplitude on the straight track segments after the curves.

The accelerations on several structural elements of the railway vehicle are also studied. It is observed that the wheels wear has a negligible influence on both non-compensated and vertical accelerations.

The influence of the wheel wear state on the vehicle-track loads show that, when travelling in curves, the vehicle assembled with worn wheels originate higher ripage forces on wheelsets 1 and 3. On the other hand, the wheelsets 2 and 4 with new wheels transmit larger lateral track forces to the track. The results also reveal that, in the straight track, the wheel wear has no influence on the vertical contact forces. When running on a curve, the worn wheelsets 1 and 3 have slightly higher vertical forces on the outer wheels and lower loads on the inner ones.

The results for the derailment coefficient show that for wheelsets 1 and 3 the values are higher when using worn profiles. The opposite happens in wheelsets 2 and 4, where the larger values of the derailment coefficient occur when the wheelsets have new wheels. In all wheelsets, the values obtained for the derailment coefficient are more than 50% below the critical levels.

1

J. Pombo, J. Ambrósio, M. Pereira, R. Lewis, R. Dwyer-Joyce, C. Ariaudo, N. Kuka, "A Study on Wear Evaluation of Railway Wheels based on Multibody Dynamics and Wear Computation", Multibody Systems Dynamics, 24(3), 347-366, 2010. doi:10.1007/s11044-010-9217-8

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