When designing and optimizing a rail vehicle there is a contradiction between, on the one hand, stability on straight track at high speed and, on the other hand, reasonable wheel and rail wear in small- and medium radius curves. Higher speeds require to some extent stiffer wheelset guidance to avoid hunting and ensure stability. However, with stiffer wheelset guidance the risk of increased wheel and rail wear in curves is imminent. In this paper, the process of developing and optimizing a track-friendly bogie is described. A multi-body system (MBS) simulation model was used, taking due consideration to nonlinearities in suspension and wheel-rail contact, as well as realistic flexibilities in the track. Adequate and systematic consideration is taken to a wide range of possible non-linear wheel-rail combinations. Dynamic stability is investigated both on straight track and in wide curves at high speeds. The balance between flange wear and tread wear is studied in order to maximize wheel life between re-profiling operations in the intended average operation. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering, which in combination with appropriate yaw damping ensures stability on straight track at higher speeds. The bogie has been subject to both certification testing and long-term service testing in the Gröna Tåget (the Green Train) research and development programme.

The cost of maintaining and renewing railway tracks affected by traffic-dependent deterioration is considerable. It is important not only to have proper maintenance regimes, but also to have knowledge of the interaction between vehicles and track in order to reduce the deterioration of both. In a joint project between Banverket (Swedish Rail Administration) and KTH (Royal Institute of Technology, Stockholm), a model for track deterioration is developed, considering track settlement, component fatigue, abrasive wear, and rolling contact fatigue of rails. The basis of the model is taken from what is considered as state-of-the-art knowledge. The model is used as a basis for a proposed new track access charging regime for Banverket, able to differ between vehicle types based on their characteristics and tendency to deteriorate the tracks. The model is implemented in an Excel® environment and applied to Swedish mainline traffic and vehicles. Using representative vehicle characteristics in determining track deterioration, it is predicted that there are large differences between different vehicles regarding their deterioration of the tracks. The model predicts axle load, unsprung mass, and wheelset steering capability as decisive for track deterioration. The model is believed to predict realistic results also for heavy-haul rail operations.

Rail vehicle axle failure on the outside of the wheels : means of minimizing the risk of derailment

Link suspension is the most prevailing suspension system for two-axle freight wagons and still frequently used for four-axle freight wagons in central and western Europe. The system design is simple and has existed for more than 100 years. However, still, the characteristics are not fully understood. This article focuses on the lateral characteristics of the link suspension. First, results from stationary measurements on freight wagons and laboratory tests on single links are presented. Then, a simulation mathematical model is proposed. Finally, the influence of various parameters on the link characteristics is investigated. With the developed simulation model, many of the stability problems of link suspension running gears can be explained, but further research is needed to fully understand the characteristics and to be able to recommend improvements. From the tests, it also becomes obvious that the characteristics of different links can vary significantly from each other depending on age and maintenance status.

This paper describes the methodology for safety assessment related to the risk of a train overturning in strong cross-winds. As an example, this methodology is applied on the high-speed line Botniabanan being built for a maximum speed of 250 km/h in the northeast coastal region of Sweden.The process starts with a systematic identification of locations along the line having a potential high risk of overturning due to cross-winds. This is followed by a cross-disciplinary study. The first step is to estimate the probabilities of wind velocity and wind directions. The next step is aerodynamic computation of overturning forces and moments acting on relevant types of train. Further, the critical overturning wind velocity is determined by a multi-body simulation technique. Finally, the overturning accident frequency is calculated. The calculated risk is compared with generally accepted risk levels in modern train operation.

Summary Besides higher average speed and a higher number of yearly train kilometres, an improved space utilisation is a very efficient mean to increase productivity and reduce train traffic cost. One of the possibilities to do so is to introduce high-powered wide-body multiple unit trains.

This paper initially describes the main features of the radial selfsteering bogies, which have been developed for the high speed train X2000, suburban trains and other applications. One of the main goals with these bogies is to reduce lateral track forces at high speed curving.This development has been supported by extensive theoretical investigations parallel to practical tests and verifications. Since around 1973 the main tool for theoretical analysis has been rime domain simulations of non-linear vehicle-track models under influence of perfect and irregular track geometry. There are models for vertical/longitudinal and for lateral dynamics. The models are assembled and utilised in a specialised computer program, SIMFO, and in a more general computer code, GENSYS, the latter having full 3-dimensional capability.A frequently used model for lateral dynamics of a four-axle bogie vehicle with 37 degrees of freedom (DOF) is shown as an example. In order to avoid an unrealistically stiff lateral coupling between wheel axles and ground, this model contains lateral track-ground elasticity and/or lateral and torsional DOF for each wheel. By comparison with measurements it is shown that characteristic quasistatic and dynamic behaviour can be simulated with accuracy.