The diffusion of the High Speed Train in Europe has determined the necessity to define standards for the trains and the tracks in order to guarantee the same level of comfort in the entire European network. The wheel forces due to the interaction of the running train and the infrastructure are one of the elements to limit. Instead these forces produce not only discomfort to the passengers, but also negative effects on the infrastructure, like mechanical wear of the tracks, fatigue damage accumulation on bridges and vibrational disturbance of precision machines near railway tracks. Dynamic train wheel forces were analysed in this numerical study. Rail roughness with wavelengths from 0.01 to 20 m and wheel roughness of with wavelengths from 0.01 to 1 m were included in the model. Velocities between 60 and 250 km/h and wide range of possible subgrades and rail pads have been analysed. Determination of a proper model for rail and wheel roughness proved to be difficult, since different literature sources show different wavelength ranges. This problem was handled by combination of the information and by extrapolation. The influence of particular parameters was examined by calculating of a large number (96000) of transient dynamic simulations with varying input parameters. All input parameters: train velocity, rail roughness, wheel roughness, track stiffness and train properties showed a distinct effect on the resulting contact forces and wheel accelerations. This makes visualization as well as simple interpretation difficult because of dimension of the problem. Generally it can be stated that high train velocities, high roughness and high track stiffness cause high dynamic effects. The relationship between the input (velocity, roughness, etc.) and output (wheel forces, etc.) variables was captured by regression of different polynomial models. Models with higher order provided a better fit. Prediction of force spectra using these models is more accurate at higher frequencies, as it was shown by standard deviation of the prediction error. Visual comparison of third-band wheel force spectra showed that a track with high roughness (6dB above mean value) and low train speed of (ca.70 km/h) produces dynamic wheel forces similar to a track with low roughness (6 dB below mean value) and high train speed (ca.240 km/h) in range 4-16 Hz. However, such judgment based on visual comparison should be used carefully, and the created regression models should be preferred. Track stiffness showed negligible effect on low bands offeree spectra (up to 16 Hz), but the effect was distinct in higher frequency bands (from 20 Hz).
Dynamic train wheel forces: numerical parameter study
2012
15 Seiten, 14 Bilder, 7 Tabellen, 12 Quellen
Conference paper
English
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