Stability Of Railway Vehicles Research Articles

Design of Small-Scaled Derailment Simulator for Investigating Bogie Dynamics

The dynamic stability of railway vehicle has long been one of the important issues in railway safety. The dynamic simulator has been used as a tool for investigating the dynamic stability of railway vehicles and wheel/rail interfaces. In particular, small scale simulators have been widely used in laboratory studies instead of full scale roller rigs which can be quite costly and rather inconvenient for testing out the effect of diverse design parameters. But techniques for design of a small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail systems and the bogie systems have not been well developed in Korea. Therefore, a research on the development of a small scale simulator for investigating bogie dynamics needs to be undertaken. The present paper investigates design of a small-scaled derailment simulator and the design of a small scale bogie. The simulator developed can be used to investigate the effect of diverse parameters such as attack angle, wheelbase and cant on dynamic behavior of the bogie and key dynamic performance parameters such as derailment coefficient and critical speed.

Lateral Hunting Stability of Railway Vehicles Running on Elastic Track Structures

Considering the viscoelastic property of railway track structure, it is suggested in this paper to include the influence of track dynamics in calculation of lateral stability of railway vehicles running on tracks. A direct numerical method based on the stability of time histories of vehicle components is proposed to ascertain the nonlinear critical hunting speed of railway vehicles. The time histories of the vehicle system are calculated by use of the three-dimensional vehicle-track coupled models, which are capable of taking into account the influence of dynamic properties of track structures on vehicle dynamics. The effect of track system properties such as the rail fastener stiffness and the rail profile on the lateral hunting stability of the vehicle is investigated. Differences of the critical hunting speeds of vehicles on rigid track model and on elastic track model are found out. Generally, the rigid track model overestimates the critical hunting speed by 5–10% for different types of vehicles, which implies that the classical vehicle dynamics predicts higher lateral stability of a vehicle than the vehicle-track coupled dynamics does. This conclusion is of significance to the safety design of railway vehicles and should be taken notice in the design stage. The reason that causes the differences is discussed. A full-scale field experiment was carried out to investigate the hunting behavior of a freight car with three-piece bogies on a straight track. Very obvious hunting motion was observed in the experiment when the unloaded vehicle ran at the speed of 75 km/h, which verified the theoretical calculation results.

Study on the Running Vibration Characteristics of Railway Vehicle

In this paper, in order to investigate a contact area between the measured profile of wheel and the designed shape of rail, we carried out calculation of the contact area strictly by a general software program, which applied the boundary element method and half-infinite body approximation. In addition, a calculation method of a creep coefficient is proposed with focus on contact areas between actual wheel and rail. Moreover, we also carried out numerical simulation of the running stability to find out how the difference of a value of an estimated creep coefficient has influence on the running stability of railway vehicle. As a result, it is shown that the contact area between the actual wheel and the rail has the shape composed of many contact areas, and the estimated creep coefficient may be smaller than the Kalker's theoretical value due to the influence of fine unevenness of wheel tread. Furthermore, we describes that the proposed method make the evaluation on running stability on the safety side.

Bifurcation approach to the influence of rolling radius modelling and rail inclination on the stability of railway vehicles in a curved track

This paper is devoted to the problems of stability of railway vehicles in a curved track. The applied method is well known as bifurcation approach, based on the analysis of bifurcation diagrams being the result of numerical simulations. Nevertheless, the original elements existing in the method enable the studies of stability in curved tracks. The main new content within this article is a study of influence of two factors on the stability of two-axle railway vehicle model in curved track, and straight track as well. These two factors are the variations in rail inclinations and the way of mean rolling radius determination. Four different values of the inclination for the three wheel–rail profile combinations and four different ways of determination of mean rolling radius are the case studies here. All of them are illustrated, discussed and supplemented with concluding remarks. At the end, more general conclusions are drawn, summarising all results.

On the influence of crosswind on the overturning stability of railway vehicles

AbstractIn recent years modern railway vehicle design shows a trend to faster, lighter and more energy efficient railway systems. These developments unfortunately alter the crosswind stability in a negative manner and so the risk of overturning of railway vehicles during operation in strong winds becomes a critical issue. The risk of overturning is quantified by the probability that a railway vehicle capsizes. To improve the crosswind stability it is very important to know the influence of the design and excitation variables on the wheel unloading of the railway car. Sensitivity coefficients of the design and excitation variables with respect to the probability of failure are calculated and the most influential variables are accentuated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reliability based analysis of the crosswind stability of railway vehicles

The computational models used to assess the crosswind stability of railway vehicles by multibody simulation (MBS) are affected by large uncertainties. Especially, the aerodynamic loads acting on the vehicle are difficult to model and the respective parameters cannot be easily acquired. Such uncertainties are usually neglected in the safety norms even though their effects on the risk assessment can be very large. In this paper the problem is tackled by modelling the most influential but uncertain parameters as stochastic variables. The resulting task can be efficiently managed by reliability techniques, mainly inherited from structural mechanics. This finally leads to the substitution of the conventional characteristic wind curve (CWC) by the probabilistic characteristic wind curve (PCWC). The proposed approach is referred to the most recent European norms for crosswind stability and exemplified on the test case of a German high speed train (ICE2).

Active yaw damper for the improvement of railway vehicle stability and curving performances: simulations and experimental results

To further increase passenger train comfort and handling performances, a mechatronic approach to the design of railway vehicles is necessary. In fact, active systems on board a railway vehicle allow to push design barriers beyond those encountered with just passive systems. The article deals with the development of an electro-mechanical actuator to improve the running behaviour of a railway vehicle, both in straight track and curve. The main components of the active system are a brushless motor and a mechanical transmission, used to apply a longitudinal force between the carbody and the bogie of the vehicle. The actuator is operated in force control. Different control strategies were developed for straight track running, where the aim is to increase the vehicle critical speed, and for curve negotiation, where the goal is to reduce the maximum values of track shift forces. A mathematical model of the railway vehicle incorporating the active control device has been developed and used to optimise control strategies and hardware set-up of the active device and to estimate the increase in operating performances with respect to a conventional passive vehicle. The active control device has then been mounted on an ETR470 railway vehicle, and its performances have been evaluated during in-line tests in both straight and curved tracks.

Stability analysis of railway vehicles and its verification through field test data

Dynamic stability is one of the important performance indices of railway vehicles. In the present paper, a twenty‐eight‐degree‐of‐freedom dynamic model is proposed to study the response and stability of railway vehicles. Nonlinear quantities existing in the railway vehicle system such as conicity, track irregularity and contact force between the wheel and rail are considered. Numerical simulation is performed based on a type of vehicle currently operated by Taipei Rapid Transit Corporation along with different kinds of track irregularity as random inputs. The stability of the vehicle is discussed in detail and compared with other full‐scale test data available. It is found that the simulation result is in good agreement with the test data. Both of them indicate the transverse acceleration of the bogie meets the required stability criteria set by authorities for mass rapid transit vehicle systems. With regard to the car‐body, when the vehicle is operated below the speed of 148 km/h, the lateral throw of the car‐body is found to be below the required level. To avoid flange contact, the lateral excursion of the wheel‐set is examined as well. It is found that flange‐rail contact will not occur very frequently for the studied vehicle when operated at its regular service speeds. It is concluded that the dynamic model is appropriate for the stability study of a railway vehicle, and the dynamic performance of the studied transit vehicle is quite good.

Development of the method and analysis for non-linear lateral stability of railway vehicles in a curved track

This article is the authors’ most recent publication on railway vehicle lateral stability in a curved track. Developed procedures constitute the original and mature method of stability analysis, which is presented here. The method is based on the analysis of bifurcation plots built as a result of numerical simulations for a wide range of curve radii and straight track, as well. Despite the development of the method, new areas of its application are presented. These are studies on the influence of various factors on the stability. These factors apply to the variation of vehicle suspension parameters, wheel–rail profiles, and wear of the wheel–rail profiles in terms of both the magnitude and the type. Also, new forms of result presentation have been employed.

History of Stability of Railway and Road Vehicles

Stability of running of vehicles is one of the important design criteria of railway and road vehicles. Railway vehicle stability is based on kinematics as well as contact mechanics. It reaches back to the 19th century and had its first hey-day with the work of Carter and Rocard on stability of locomotives. A rediscovery of their knowledge, which seemed to have been forgotten, was inevitable due to increased vehicle speeds since the early Fifties. — Though investigations on road vehicle stability only began approximately in 1930 with the treatment of the shimmy phenomenon, realistic solutions were available at the same time as for railway vehicles. Besides considering historical aspects we discuss in the paper links which exist between both approaches; open questions are described.

Study on Vibration Control and Its Effect on Ride Quality and Running Stability of Railway Vehicles.

Study on Vibration Control and Its Effect on Ride Quality and Running Stability of Railway Vehicles.

Fundamental consideration of geometrical contact between wheel and rail.

To prevent the hunting and to raise the running stability of railway vehicles, it is extremely important to make clear the geometrical contact between the wheel and the rail. In this paper, the contact geometry between the rail and the wheel tread profile consisting of one circular arc forms, is analyzed theoretically in detail, and the exact solutions are compared with the approximate formulas. The theoretical analysis has made clear the following points. There is an inclined angle between the horizontal line and the center line of the wheelset due to the lateral displacement of the wheelset. There are also a variation of the radius of the wheel at the contact point between the wheel and the rail, a vertical displacement at the center of gravity of the wheelset, an effective conicity at the contact point, a variation of the radius of the wheel originating in the radius of the wheel of a roller rig such as the test stand of a vehicle, and a variation of slope at the contact point due to the angular displacement of the wheelset, and so on.

Effects of Truck Design on Hunting Stability of Railway Vehicles

A general model of a dual-axle railway vehicle truck is derived. By suitable choices of primary suspension elements, this general model may be specialized to become (1) a roller-bearing freight truck, (2) a plain-bearing freight truck, (3) a roller-bearing truck with primary suspension elements, (4) a passenger truck, (5) a generic model of a freight truck with interconnected wheelsets, or (6) a rigid truck. The truck model is combined with a car body capable of lateral and roll displacements. The effects of the various design parameters on the critical speed for hunting are examined for each configuration.

Steering and Dynamic Stability of Railway Vehicles

SUMMARY For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a sing...