Testing the Effectiveness of the Anti-Bending Bar System to Reduce the Vertical Bending Vibrations of the Railway Vehicle Carbody Using an Experimental Scale Demonstrator

In this paper, the vertical vibration behaviour of an experimental scale demonstrator of a railway vehicle carbody fitted with an anti-bending bar system of innovative design is studied to highlight its ability to raise the bending natural frequency of the railway vehicle carbody and to reduce the intensity of the vibration. The anti-bending bar system has been previously proposed by the second author as a new passive method to improve comfort in passenger coaches with long carbodies that have a natural bending frequency located in the range of maximum sensitivity of human beings to vertical vibration. The experimental scale demonstrator consists of an aluminium plate supported on four rubber supports. The aluminium beam reproduces to a scale of 1:10 the length of a passenger coach carbody, and its thickness is set so that the first bending frequency of the plate is close to the usual value of real carbodies. The anti-bending bar system consists of two steel bars arranged longitudinally in the middle of the aluminium plate, near its side edges. Each anti-bending bar is fixed at the ends to the aluminium plate by joints consisting of a clamping arm welded to a fixing flange. The two anti-bending bars oppose the bending movement of the aluminium plate, thus increasing its bending stiffness. This results in increasing the bending natural frequency of the aluminium plate and reduction its vibration. Testing the effectiveness of the anti-bending bar system consists of experimentally determining the frequency response of the aluminium plate acceleration without/with the anti-bending bar system by the impact hammer method. The experimental results show the first bending natural frequency increases from 9.01 Hz to 13.4 Hz and the acceleration amplitude decreases by more than 50% when the anti-bending bar system is used. To confirm these results, a theoretical model of the experimental scale demonstrator based on the finite element method was developed. The results obtained with this model are in line with those obtained experimentally.