The paper herein analyzes the ride comfort at the vertical vibrations of the railway vehicle, evaluated by two methods—mean comfort method and Sperling’s method. The two methods have in common that the estimation of the comfort sensation is conducted with the comfort indices, namely ride comfort index NMVZ and ride comfort index Wz. The values of these indices are derived from numerical simulations. The advantage of using the results of the numerical simulations versus using experimental results, on which most previous research is based, resides in the fact that the ride comfort indices can be examined while taking into account the influence of velocity and certain parameters altering the behavior of vertical vibrations of the carbody, i.e., carbody flexibility and the suspension damping. The numerical simulation applications have been developed based on a theoretical model of the vehicle that considers important factors affecting the behavior of vertical vibrations of the carbody, by means of a ‘flexible carbody’ type model and an original model of the secondary suspension. The results presented mainly show that the two assessment methods lead to significantly different outcomes, in terms of ride comfort, under identical running conditions of the vehicle.
The paper features the results of a numerical study regarding the influence that the damping reduction in the primary suspension of the rail vehicle, due to the defect in a damper, has on the ride comfort. The study is based on model of rigid-flexible coupled vehicle, with seven degrees of freedom, where the carbody is modelled as an Euler-Bernoulli type equivalent beam. The results of the numerical simulations show the power spectral density of carbody vertical accceleration and the ride index comfort calculated in three carbody reference points - at the centre and against the bogies, for various cases of reduction in the damping constant of the primay suspension in the axle, compared to the reference value. As a function of velocity, due to the geometric filtering effect, the damping reduction has contrary effects upon the level of vibrations in the carbody and upon the ride comfort.
Ride comfort is one of the criteria for evaluating the dynamic behaviour in railway vehicles, through which the complex sensation triggered by the vibrations in the railway vehicle carbody upon passengers is being described. The behaviour of vibrations along the vehicle carbody is not uniform and the point where the ride comfort is the least convenient can be considered as the carbody critical point. The paper examines the ride comfort along the carbody and the position of the ride comfort critical points in correlation with the speed, carbody flexibility and suspension damping. To this purpose, there are used the results from numerical simulations regarding the ride comfort index calculated along the carbody and the ride comfort index in three points deemed relevant in terms of evaluating the ride comfort at the center of carbody and above the bogies.
The theoretical research on means to reduce the vertical vibrations and improve the ride comfort of the railway vehicle relies on a mechanical model obtained from the simplified representation of the vehicle, while considering the important factors and elements affecting the vibration behaviour of the carbody. One of these elements is the anti-yaw damper, mounted longitudinally, between the bogie and the vehicle carbody. The anti-yaw damper reduces the lateral vibrations and inhibits the yaw motion of the vehicle, a reason for which this element is not usually introduced in the vehicle model when studying the vertical vibrations. Nevertheless, due to the position of the clamping points of the anti-yaw damper onto the carbody and the bogie, the damping force is generated not only in the yawing direction but also in the vertical and longitudinal directions. These forces act upon the vehicle carbody, impacting its vertical vibration behaviour. The paper analyzes the effect of the anti-winding damper on the vertical vibrations of the railway vehicle carbody and the ride comfort, based on the results derived from the numerical simulations. They highlight the influence of the damping, stiffness and the damper mounting angle on the power spectral density of the carbody vertical acceleration and the ride comfort index.
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