Perpustakaan Digital ITB

Nowadays, in line with the increasing of train operational speed, lighter rail vehicles are required for operational efficiency, higher capacity, and lower track maintenance cost. However, the carbody lightweight structure design tends to have lower stiffness which can lead to the lower carbody first bending mode frequency. In the other hand, higher operating speed increases the excited frequency that the vehicle receives from the wheel-rail interaction. It can cause resonance if the two frequencies coincide. In such conditions, the carbody structural vibration will increase and worsen the comfort level of passengers. As reported in literatures, several studies have been conducted to reduce the carbody structural vibration at low frequencies by increasing the stiffness of the carbody structure, adjusting the secondary suspension parameters, and setting the under-chassis equipment (UCE) as the dynamic vibration absorber (DVA). However, no studies have examined the effectiveness of these three alternative solutions in reducing the carbody structural vibration. Thus, this present study means to determine the correlation between the carbody stiffness, the vehicle secondary suspension, and the UCE layout and suspension to the carbody first bending mode vibration caused by excitation from the wheel-rail interaction transmitted by the bogie suspension system to the carbody. The study used a numerical simulation model validated by an experiment of a simple scaled rail vehicle model to obtain the Pearson correlation coefficient between the vehicle parameters and the carbody structural vibration. According to the results, selecting the longitudinal bar first vertical bending frequency to represent bar parameters provides a positive high correlation with the carbody system first bending frequency. On the other side, the bar frequency has a negative correlation with the magnitude of the carbody system first bending vibration. Data merging should be more selective; it is better to split the correlation analysis based on the length of the bars. Selecting the appropriate dimensions for the bars will increase the flexural stiffness of the carbody without significantly adding mass to the carbody, allowing for an optimum improvement of the carbody system first bending frequency. The stiffness of the secondary suspension is highly positively correlated with the carbody first vertical bending frequency. Although it correlates positively, increasing the suspension stiffness has side effects, causing an increase of the carbody rigid mode frequencies close to the range of human sensitivity to vertical vibrations. Further analysis may be required to select the proper secondary suspension stiffness with the consideration of the combination of the carbody flexible and rigid mode vibrations. The UCE frequency produces a non-linear correlation against the carbody system first bending frequency. The relation shows a particular non-linear function. Using a higher UCE frequency than the initial carbody system first bending frequency will lead to a decrease in the bending frequency. This value will then gradually increase with the increasing UCE frequency but cannot exceed its initial bending frequency. Using UCE as a DVA will be optimum if the applied UCE frequency is slightly below the initial carbody system first bending frequency. The UCE with flexible support can work as DVA to shift the carbody system first bending frequency; however, its effect on the rigid mode is marginal.