High-Velocity Trains And An Ever Tighter Schedule
Ever faster trains and an ever tighter schedule result in stress to rails, undercarriages, and track foundations yet unknown. The resulting wearout can not only result in expensive repairs but also in accidents. With this background the Deutsche Forschungsgemeinschaft (DFG) already in 1996 set up a priority programme "system dynamics and long-term behaviour of undercarriages, tracks, and foundation", that is sought to investigate these stresses scientifically and make predictions on the long-term consequences. The programme has now yielded its first results: models have been established that allow the prediction of wearout and damage of undercarriages and rails.
In about 20 projects scientists have now been working for two years on answering the question which consequences the change of single factors of the railways system - e.g. greater velocity or new materials - has in the long-run on other components of the system. Often such consequences become visible only a long period after the change has been introduced. The wearout of metal-made components, i.e. wheels and rails, as well as the settlement of the track foundation as a result of repeated stress are of particular interest. The DFG has granted five million marks for the first two-year funding period, another five million marks have just been granted for the second period.
"The system has come to the limit", explains one of the initiators of the DFG programme, Professor Dr. Klaus Knothe of Technical University Berlin, the "basic hypothesis". In addition, there were no "rules of thumb" to draw back on as is commonly done in "regular" railways technology since high-velocity trains are not yet long enough on service. Thus the "short-term dynamics", e.g. vibrations that are felt as roaming and rattling, is gathered systematically and is then set into relation with long-term damages.
"We can now predict quite well what happens to metal parts in the long-run", says his colleague and co-initiator of the priority programme, Professor Dr. Karl Popp of the Institute for Mechanics at the University of Hannover. The researchers were able to develop models that express in formulas what happens upon stress. The knowledge thus obtained not only allows to predict wearout - for the first time conclusions can be drawn on the lifetime of parts long before the first parts are torn and have to be replaced. In addition, the cost effectiveness of tracks and single components can be judged.
On the basis of these models a better concept of the whole system can be achieved and by adjusting velocities and train schedules the occurrence of damages can be retarded or even completely avoided. In the future, the models developed could serve as aids for the reconstruction of accidents and for damage analysis, although such considerations are not on the agenda of the priority programme.
The scientist are still facing obstacles in the attempt to develop a similar model for the effect of stress on the track's ballast since highly complex processes are active there.
The German railways corporation (Deutsche Bahn AG) co-operates closely with the researchers and supports the programme by providing data, by giving them the opportunity to participate in measuring campaigns and by attaining the regular meetings of the scientists.