RAILWAY VEHICLE RESPONSE UNDER RANDOM IRREGULARITIES ON A TANGENT TRACK – NONLINEAR 3D MULTI-BODY MODELLING

Safety and ride comfort are the main issues in railway industry that have to be harnessed and well controlled, especially when the operating speed is increasing continuously. Actually, many studies are performed in that matter in order to assess the risks of derailment of a railway vehicle and determine the level of exposure of passengers to the mechanical vibrations. However, the assumptions made turned out to be often inadequate, especially when it comes to consider that the lateral movement of the wheel-axle set adhere perfectly to the transversal track irregularities. Our study is presenting the results of a dynamic 3D-modelling of a full railway vehicle, and comparing its response when exposed to the track disturbances with real measurements performed in each part of it. To that end, 27 degrees of freedom are describing the vibration of each part of the vehicle. The simulation is carried out by Matlab. Regarding the rail/wheel contact issue, we have needed to adopt the linear theory of rolling contact developed by Kalker to estimate the creep forces. Moreover, the rail/wheel contact geometry is evaluated according to UIC 519 leaflet which gives an approach that allows us to summarize the contact area to a conical wheel on a knife-edged rail. The angle of such wheel is named equivalent conicity and depends on the rail profile, the wheel profile, the rail cant, the track gage and the initial lateral displacement. A computer based-program is developed with Matlab to determine this parameter and it's validated according to the recommendations of the leaflet mentioned earlier. On the other hand, track irregularities are measured using an inertial measurement unit (IMU) which has the advantage to provide the accurate track parameters defined in the standard EN 13848-1. This system was validated according to the recommendations of the standard 13848-2. Finally, the results are compared in the frequency domain to the vibrations measured on a vehicle travelling over the track considered in our simulation and show the effectiveness of the proposed model.