26th ANNUAL WHEEL RAIL INTERACTION CONFERENCE

Abstract:

Harmonic Vehicle/Track Interaction: Using Simulation Tools to Increase Train Speeds and Safety Assurance

This study uses multibody simulation to analyze the dynamic behavior of vehicles subjected to harmonic excitation. Through two case studies at MRS Logistica the authors intend to clarify how the phenomenon happens in practical terms and its impact on railway operations and safety. For this purpose, the excitation frequencies that may cause resonance in tangents and submit the vehicles to the risk of derailment were identified. The excitation frequencies were obtained by variation of the speed and using characteristic wavelengths of MRS Logistica S.A. considering the parameter of cross-level irregularity. Signal processing techniques were used to identify within the wavelength ranges which could be considered potentially harmful to harmonic roll mode. The track measurements were performed by TrackSTAR. These wavelengths were determined using the STFT (Short Time Fourier Transform) method. The vehicles’ natural frequency was identified using the eigenvalue and transient method of VAMPIRE dynamic simulator. The simulations were also made through VAMPIRE with the purpose to obtain the amplitude response for the parameters of derailment as L/V and wheel unloading, according to the criteria of the AAR. With the results of the response amplitude for different combinations of natural frequencies and excitation frequencies produced a map of responses that can be quickly used to determinate critical combinations of vehicle, track and train operation. Therefore it is possible to compare the dynamic behavior of vehicles, approve train speed increase, analyze track maintenance and it can also be useful for the investigation of derailments. This work also offers a brief overview about track/vehicle modeling and what the requirements are to perform a simulation close to reality.