Dynamic Wheel/Rail Benchmark Single Wheelset without Friction
FRA/DTT Cooperation Team
Under a joint memorandum of understanding, rail safety experts from the French Land Transport Department (Direction des Transports Terrestres - DTT) and the US DOT Federal Railroad Administration (FRA) have been conducting simulation studies to determine the influence of track geometry anomalies on vehicle safety. DTT, which is part of the French Ministry for Infrastructure, Transport, Housing, Tourism and the Sea, regulates the rail transportation sector in France. The analyses are designed to understand the significance of differences between the well-established French limits for maintaining track geometry for high-speed rail operations and the corresponding U.S. track geometry standards enacted in 1998 for the same purpose. Both standards attempt to limit the maximum allowable deviations in track geometry through different methods that do not always yield the same values. Furthermore, they do not adequately address other requirements for permitting higher speeds through curved tracks (higher cant deficiency). While higher cant deficiency operations are not of priority in France due to limits on curvature imposed by design on their high-speed lines, they are of importance to current and future higher speed rail operations in the US, which may require faster travel on existing tracks with sharper curves. Results of this collaboration are directly benefiting an ongoing FRA effort for revising current track safety standards for high-speed rail operations in the US.
As part of the joint effort, the team has also focused on computer simulation tools used for predicting the dynamic behavior of rail cars due to their running interaction with track. Results of the work described above indicated the possibility that not all simulation codes are fully optimized for safety studies. Specifically, extreme conditions involving separation and subsequent resumption of contact between wheel and rail are not necessarily well predicted by all simulation tools. The careful and accurate prediction of rail vehicle behavior under such extreme conditions, while of less significance to ride quality studies, is however essential to proper safety studies. As a result, benchmarking examples were developed by Dr. Pascal to differentiate simulation codes that are more geared towards safety studies. The benchmark, named LD Benchmark, is expected to significantly contribute to a better fundamental understanding of high speed rail safety.
| Jean Pierre Pascal
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