Papers by Keyword: Railway Vehicle

Abstract: 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.

Abstract: Jointed track is still used to build the secondary lines where the maximum speed does not exceed 100-120 km/h. Jointed track construction is based by the fact that the rails are joined end-to-end via the rail joints in order to assure the continuity of the rolling surface of the rails. The rails are jointed using two metal joint bars (fishplates) bolted to the ends of adjoining rails. The rail joints are featured with small gaps to allow the thermic expansion of the rails when the environmental temperature is higher than that during the fitting. In this paper, an analytical model for the rail joint considering the influence of the joint gap is presented and analysed. The model consists of three Euler-Bernoulli beams, two for the rail ends of the rail joint and the third beam for the two joint bars, connected to the rail ends by a Winkler layer. The concept of weakness of the rail joint (rail joint deflection/continuous rail deflection) is introduced and used to analyse the static behaviour of three types of rail joints used at CFR (Romanian Railways). The influence of the joint bars length and bending stiffness, and the influence of the joint gap length upon the rail joint weakness is pointed out.

Abstract: The paper originally investigates the influence of the admitted ranges of slow-acting filling time of brake cylinder on longitudinal dynamics of freight trains, using experimental air pressure data obtained in tests on filling characteristics. Mechanical and pneumatic models are summarized and numerical simulations were performed for a train composed of six wagon train, in different filling characteristics configurations. The results reflect significant effects on in-train forces values, while evolution and disposition of compression and tensile forces between neighbored vehicles in the long of the train are also affected.

Abstract: The paper investigates the effects of mechanical wheel slide protection devices (WSPD) on the braking capacity for coaches equipped with disc or cast iron block brakes. Decelerations and jerks, that affect the passengers comfort, are also analyzed. An original simulation program, based on experimentally determined air pressure evolutions in brake cylinder is used for this purpose. Results of numerical simulations show that in the case of repeated actuations of mechanical WSPDs, disc brake vehicles are more affected in terms of braking capacity. Regarding jerks during braking actions, in both normal and low adhesion conditions, vehicles equipped with high power cast iron block brake with two pressure levels prove to be more affected.

Abstract: The paper focuses on evaluating the stability of the railway vehicle during running on a track horizontal irregularities and investigating the possibilities to improve the dynamic behavior on a lateral direction. The evaluation method for the stability relies on the homologation specifications of the railway vehicles from the perspective of the dynamic behavior included in the UIC 518 Leaflet, where the lateral accelerations of the bogies represent evaluation units for the stability. The lateral accelerations are derived from numerical simulations, developed on a non-linear complex model of the vehicle/track system, where the vehicle is described by a mechanical system with 21 degrees of freedom. The results thus presented outline the possibilities of improving the vehicle stability by adopting the best values of the lateral damping of the secondary suspension or of the lateral stiffness of the primary suspension that will lead to the minimizing of the lateral acceleration in a bogie.

Abstract: Two main factors for design of railway vehicles are stability and curving performance. Running performances, result from stiffness design of a primary suspension, between stability and curving are contrary to each other. The more longitudinal stiffness of a primary suspension stiff, the better straight performance is outstanding, however, curving performance is degenerated. Also, if the less longitudinal stiffness stiff, running performance has opposite characteristics. Curving performance of railway vehicles should be outstanding on small curved track which is in cities. If curving performance is improved, lateral contact force (i.e. flange contact force) of wheel and rail is decreased by improved spring so, wear and noise of wheels are decreased. Derailment risk from wheel and rail contact, of course, is decreased. Thus, it's important to design an axle spring of a primary suspension. The design of ensuring stability performance, of course, should be precede. An axle spring is designed using FEM tool which is ABAQUS also, rubber like material is modeled by Mooney-Rivlin model. Developed FE-axle spring model is analyzed and is produced also, this model is validated by test results of a load tester.

Abstract: A fully equipped railway vehicle dynamic model which considers the car body flexibility is established to analyze the fundamental reason of car body flexural resonance. Results show that it is the geometric filtering phenomenon rather than the natural vibration of bogie bounce that causes the car body resonant flexural vibration. The higher the vehicle running speed, the higher the first vertical bending frequency should be required.

Abstract: The paper focuses on the validation of the numerical simulations regarding the behavior of a railway vehicle while running on a track with irregularities. These simulations are developed from a complex vehicle track system that allows the evaluation of the dynamic behavior on a vertical direction of the railway vehicles in terms of running quality, vibration comfort and the fatigue stress on the track. The validation process consists in the comparison of the acceleration spectra derived from numerical simulations and those from the data recorded during the vehicle circulation on the running line. In this context, the frequency spectra of the measured acceleration are shown that they can be classified into two categories one is of the spectra similar in shape with the ones considered in the numerical simulations, used as a basis for the validation process and the other one includes the acceleration spectra that are sensibly different than the ones derived from the numerical simulations.

Abstract: During circulation the railway vehicle is subjected to the action of dynamic forces under the effect of shocks that appear in the driving system caused by stick slip phenomenon, dynamic forces arising from the rolling process when the wheelset is passing over accidental vertical unevenness of the track and also longitudinal dynamic forces occurring in the case of buffering, respectively those caused by frontal impact (the crash forces). The present paper presents the mechanical and mathematical models which are underlying the evaluation of the magnitude of these forces as well as their effects on the resistance of supporting structure of the vehicle and on traffic safety.

Abstract: Analyzed and studied the hydro-pneumatic buffer structure of railway vehicle, designed a new type of hydro-pneumatic buffer and established the detailed dynamics model. Calculated the static characteristic curve of hydro-pneumatic buffer with different compression rate and dynamic characteristic curve with different impact speed through the numerical simulation method. The simulation results shows that the biggest impedance force is 1836.3KN and buffer capacity reach 221.89KJ when impact velocity of the new hydro-pneumatic buffer is 5m/s.New hydro-pneumatic buffer can improve the speed of manipulating vehicle, reduce the longitudinal impact and vibration in the train and adapt to the needs of the trains.