Session: 17-01-01: Research Posters

Paper Number: 137425

137425 - Assessing Rail Damage in Turns Due to Lateral Load Transfer 

The rate at which the railway infrastructure rails are damaged due to railway cars is a function of a multitude of parameters and operating conditions related to the environment, to the infrastructure and to the vehicle-cargo system. Amongst the vehicle design and operational conditions influencing the railway damage includes the distance between the wheelsets, the vehicle´s traveling speed and the type of cargo. In this context, the type of cargo determines several characteristics that potentially influence the rail damage potentials of the cargo, including its center of gravity position. In particular, a directional maneuver involves greater stresses on the rails, as a result of lateral load transfers (normal forces) and of the steering stiffness of the bogie (tangential forces). Such higher levels of rail stresses are supported using reinforced railway materials. In this context, however, the damage caused to the rails in curved tracks represent additional risk factors for the occurrence of railway derailment and other railways mishaps.

       Focusing on the lateral load transfers derived from the turning maneuvers, their magnitude depends on both the infrastructure design and on the vehicle characteristics, including the center of gravity position of the cargo and the stiffness of the secondary suspension. Such a condition is illustrated in Figure 1, where the center of gravity of the cargo has shifted as a result of the suspension deflection, contributing to the uneven load distribution on the railway car suspension, which is thus a function of the inertia forces (m a_N) and of the mass m weight (m g; g is the gravity acceleration), where the lateral acceleration a_N is a function of the operational vehicle speed and of the track radius. Consequently, the magnitude of the damage caused by the traffic to the rails will depend on the magnitude of such forces and the related vehicle and infrastructure characteristics, such as lateral slope and curve radius and longitude.

In this context, the different types of railway vehicles will have different railway damage potentials, as such different vehicles have different positions of their center of gravity. in other words, the rail pricing would be different for each of the vehicles in the railway traffic. Such an analysis has not been reported in the literature, as the freight prices are based exclusively on the length of the displacement and on the magnitude of the vehicles mass. In this paper, experimental results are presented, describing the testing outputs of the load transfer measured in a scale-down tilt table device, as a function of the center of gravity position of the cargo, and of the stiffness of the suspension springs.

 

While the rail damage assessed in this paper corresponds only to the lateral load transfer when the railway car is subjected to lateral accelerations, it can be assumed that the lateral load transfer represents the most important uneven stress generation at the rail body and surface. While the outputs from this paper further suggest that the rail damage is a function of the type of transported cargo, with the taller loads producing the higher stresses in the rail, the rail pricing does not take into consideration any cargo-related over-charge.

In this context, a rational rail pricing criteria could improve the economic sustainability of this transport mode, which could even represent further advantages of such a transport mode. The underlying in such a rail pricing concept, focus in charging the real damage caused to the infrastructure by their users, with a fair infrastructure pricing.

The local damage caused to the external rails of these infrastructures, should be consider in the context of the accumulated rail damage during the whole life cycle of the rails, where local effects translate into massive effects, as rail defects can originate damages to the rolling elements, and from them to the whole infrastructure.

Presenting Author: Frank Otremba Federal Institute For Material Research and Testing

Presenting Author Biography: Frank Otremba received a Dipl-Ing. Degree in mechanical engineering from the university of Rostock in 1988. The Ph.D was earned also by the university of Rostock in the field of mechanical engineering. Since 2015 he has been Honorary Professor at the Brandenburg University of Technology.
He began his professional career at the HEW and was responsible for the safety assessment of components in nuclear power plants. Before entering BAM (Bundesanstalt für Materialforschung und -prüfung), he also worked as a researcher at the University of Stuttgart. Since 2007 he has worked as head of division „Tanks for Dangerous Goods and Accidental Mechanics“. He also provides courses in mechanical engineering at the Brandenburg University of Technology. He has published more than 220 papers in serveral journals. Numerical simulations and its validation is his research area of interest. He has focussed his resaerch work on the transferbility of results to real components determined on small scale speciments.

Authors:

Frank Otremba Federal Institute For Material Research and Testing
Jose A. Romero Navarrete Queretaro Autonomous University