This paper presents a framework for simulating railway vehicle and track interaction in cross-wind. Each 4-axle vehicle in a train is modeled by a 27-degree-of-freedom dynamic system. Two parallel rails of a track are modeled as two continuous beams supported by a discrete-elastic foundation of three layers with sleepers and ballasts included. The vehicle subsystem and the track subsystem are coupled through contacts between wheels and rails based on contact theory. Vertical and lateral rail irregularities simulated using an inverse Fourier transform are also taken into consideration. The simulation of steady and unsteady aerodynamic forces on a moving railway vehicle in cross-wind is then discussed in the time domain. The Hilber–Hughes–Taylor α-method is employed to solve the nonlinear equations of motion of coupled vehicle and track systems in cross-wind. The proposed framework is finally applied to a railway vehicle running on a straight track substructure in cross-wind. The safety and comfort performance of the moving vehicle in cross-wind are discussed. The results demonstrate that the proposed framework and the associated computer program can be used to investigate interaction problems of railway vehicles with track in cross-wind. 相似文献
Track irregularities have a dramatic impact on the response and vibration of a railway vehicle and on the interaction between
wheel and rail. The random nature of the track structure and constituent materials and the effects of other factors such as
maintenance conditions and transit traffic give rise to the random nature of track irregularities. This research provides
a method to estimate the derailment probability of a railway vehicle where track irregularities are assumed to be random,
and the interaction of the track and the moving train is considered using advanced dynamic analysis. For this purpose, the
limit state function of derailment was estimated using the response surface method and advanced simulation. The probability
of derailment was then estimated using a Level 3 reliability method. 相似文献
The main objective of this article is an examination of railway vehicle dynamics during motion along a curved track. Two main aspects are presented in the paper. First, two different methods used while investigating multi-rigid body systems such as railway vehicles are discussed, i.e. the quasi-statical (or kineto-statical) and dynamical approaches. Second, two practical problems dealing with vehicle motion along a curved track are investigated. The problems under consideration refer to vibrations as well as stability, examined via finding obtained with the author's software as a result of numerical simulation. The work has both a practical and a cognitive character. The aim of the investigations is firstly to indicate the limitations of quasi-statical (and kineto-statical) methods and secondly to study the problems which cannot be treated by these methods. Two specific problems of the type investigated using a dynamical approach are the influence of track geometrical irregularities on the evaluation of vehicle ride properties and limit cycle occurrence during vehicle curve negotiation. Due to the renewed interest in the rapid passenger railway, the investigations take into consideration curves of large radii introduced along railway routes for increased velocities. Furthermore, it is shown under which conditions the obtained results may have an important practical application. This concerns the influence of vehicle suspension parameters as well as conditions of motion (speed, superelevation, curve radius, transition curve existence) on limit cycle occurrence. The limited value of conclusions dealing with vehicle ride properties obtained while using quasi-statical (kineto-statical) methods is proved through quantitative analysis. The problem of the influence of geometrical irregularities on wheel-rail pair wear is also pointed out. 相似文献
Requirements for current trains to be increasingly available have created the need to develop systems that can predict the
quality of both trains and infrastructure components. The paper presents a new approach to the detection of rail truck irregularities,
based on the measurements of bearing box acceleration during the operation of rail vehicles. The proposed procedure is based
on an inverse problem solution, estimating track irregularities from measured acceleration of the applied model of vehicle
dynamics. The simulation study of the proposed method, as well as its implementation, is presented. The method has been successfully
applied for the identification of rail irregularities on a typical Polish railroad and vehicle. 相似文献
As a vehicle passing through a track with different weld irregularities, the dynamic performance of track com- ponents is investigated in detail by using a coupled vehi- cle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are dis- cretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lat- eral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calcu- lation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an explicit integration method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail pro- file irregularity caused by hand-grinding after rail welding and track maintenances. 相似文献
The dynamic equations of multibody railroad vehicle systems can be formulated using different sets of generalized coordinates;
examples of these sets of coordinates are the absolute Cartesian and trajectory coordinates. The absolute coordinate based formulations do not require introducing an intermediate track coordinate system since all the absolute coordinates are defined in the global system. On the other hand, when the trajectory coordinates are
used, a track coordinate system that follows the motion of a body in the railroad vehicle system is introduced. This track
coordinate system is defined by the track geometry and the distance traveled by the body along the track centerline. The configuration
of the body with respect to the track coordinate system is defined using five coordinates; two translations and three Euler
angles. In this paper, the formulations based on the absolute and trajectory coordinates are compared. It is shown that these
two sets of coordinates require different degrees of differentiability and smoothness. When an elastic contact formulation
is used to study the wheel/rail dynamic interaction, there are significant differences in the order of the derivatives required
in both formulations. In fact, as demonstrated in this study, in the absence of a contact constraint formulation, higher order
derivatives with respect to geometric parameters are still required when the equations are formulated using the trajectory
coordinates. The formulation of the constraints used in the analysis of the wheel/rail contact is discussed and it is shown
that when the absolute coordinates are used, only third order derivatives need to be evaluated. The relationship between the
track frame used in railroad vehicle dynamics and the Frenet frame used in the theory of curves to describe the curve geometry
is also discussed in this paper. Based on the analysis presented in this paper, the advantages and drawbacks of a hybrid method
which employs both the absolute and trajectory coordinates and planar contact conditions in order to reduce the number of
contact constraints and relax the differentiability requirements are discussed. In this method, the absolute coordinates are
used to formulate the equations of motion of the railroad vehicle system. The absolute coordinate solution can be used to
determine the trajectory coordinates and their time derivatives. Using the trajectory coordinates, the motion of the body
in the vehicle with respect to the track coordinate system can be predicted and used in the formulation of the planar contact
model. 相似文献
The dynamic design of railway vehicles is often supported by numerical simulation performed by means of Multibody codes. Such
methodology allows to define vehicle suspensions characteristics so as to meet running safety requirements and, in the case
of passenger vehicles, to achieve an adequate comfort level. However, the effectiveness of the numerical model in the prediction
of actual vehicle behavior may fall short of requirements if the model is not sufficiently accurate. Experimental validation
can help to ensure reliability of the numerical models. In order to solve the problem, this work proposes to use experimental
tests on scaled prototypes on roller-rig for preliminary validation of the numerical model. 相似文献
This study presents a new general transient contact and slip model for tracked vehicles on hard ground which is simple, accurate, and in agreement with the test results to a satisfactory level. Simulating zero track speed instances become possible with the new contact/shear model which is the major proposed improvement in addition to more accurate results for transient steering and tractive inputs. The model represents a general tracked vehicle having rear or front sprockets, with parameters for center of gravity, wheel positions, number of wheels, and track-pretention. To calculate longitudinal and lateral forces, a transient shear model is used. Shear stress under each track pad is assumed to be a function of shear displacement. The contact time formulation used in shear displacement calculation is improved to gain accuracy for transient and zero track speed conditions.The model is implemented on the Matlab/Simulink platform and verified with a comprehensive program of road tests composed of transient steering and tractive/braking scenarios. The results of the simulations and the road tests are satisfactorily similar for both constant and transient input maneuvers. Moreover, sensitivity simulations for vehicle parameters are conducted to show that the model responses are inline with the expected vehicle dynamics behaviours. 相似文献
Based on Biot’s fully dynamic poroelastic theory, the dynamic responses of the poroelastic half-space soil medium due to quasi-static and dynamic loads from a moving train are investigated semi-analytically. The dynamic loads are assumed to be generated from the rail surface irregularities. The vehicle dynamics model is used to simulate the axle loads (quasi-static loads) and the dynamic loads from a moving train. The compatibility of the displacements at wheel–rail contact points couple the vehicle and the track–ground subsystem, and yield equations for the dynamic wheel–rail loads. A linearized Hertzian contact spring between the wheel and rail is introduced to calculate the dynamic loads. Using the Fourier transform, the governing equations for the poroelastic half-space are then solved in the frequency–wavenumber domain. The time domain responses are evaluated by the fast inverse Fourier transform. Numerical results show that the dynamic loads can make important contribution to dynamic response of the poroelastic half-space for different train speed, and the dynamically induced responses lie in a higher frequency range. The ground vibrations caused by the moving train can be intensified as the primary suspension stiffness of the vehicle increases. 相似文献
Excessive vibrations of railway vehicles induced by dynamic impact loadings have a significant impact on train operating safety and stability; however, due to the complexity and diversity of railway lines and service environment, they are extremely difficult to eliminate. A comprehensive overview of recent studies on the impact vibration behavior of railway vehicles was given in this paper. First, the sources of impact excitations were categorized in terms of wheel-rail contact irregularity, aerodynamic loads, and longitudinal impulses by train traction/braking. Then the main research approaches of vehicle impact vibration were briefly introduced in theoretical, experimental, and simulation aspects. Also, the impact vibration response characteristics of railway vehicles were categorized and examined in detail to various impact excitation sources. Finally, some attempts of using the railway vehicle vibration to detect track defects and the possible mitigation measures were outlined.
In ballasted railway tracks, one of the important components that supports the rails and distributes wheel/rail loading onto
the ballast supporting formation is a railway sleeper (sometimes is also called a “railway tie”). This paper presents results
of an experimental modal analysis of prestressed concrete sleepers in both free-free and in-situ conditions, incorporating
the dynamic influence of sleeper/ballast interaction. Dynamic interaction between concrete sleepers and ballast support is
crucial for the development of a dynamic model of railway track capable of predicting its responses to impact loads due to
wheel flats, wheel burns, irregularities of the rail, etc. In this study, four types of prestressed concrete sleepers were
in-kind provided by the Australian manufacturers. The concrete sleepers were tested using an impact hammer excitation technique
over the frequency range of interest, 0–1600 Hz. Frequency response functions (FRFs) were measured using PULSE modal testing
system. The FRFs were processed using STAR modal analysis package to identify natural frequencies and the corresponding mode
shapes for the sleepers. The conclusions are presented about the effect of the sleeper/ballast interaction on the dynamic
properties of prestressed concrete sleepers and their use for predicting railway track dynamic responses. 相似文献
As it is known, track transportation can be divided into track system above and track system below. While the train is moving, the parts above and below are interacted and influenced. Therefore, in fact, the problem of track transportation is the match between the vehicle and the railway line system. In this paper, on a basis of dynamic analysis of the vehicle-subgrade model of vertical coupled system under primary suspension, utilizing track maintenance standard and simulating track irregularity excitation, the dynamic interaction of vehicle-track-subgrade system is researched in theory and dynamic model of the vertical vehicle-track-subgrade coupled system under secondary suspension is established by compatibility condition of deformation. Even this model considers the actual structure of a vehicle, also considers vibration characteristic of the substructure of track including subgrade and foundation. All these work want to be benefit for understanding and design about the dynamic characters of subgrade in high speed railway. 相似文献
The development of efficient Weigh In Motion (WIM) systems with the aim of estimating the axle loads of railway vehicles in motion is quite interesting both from an industrial and an academic point of view. This kind of systems is very important for safety and maintenance purposes in order to verify the loading conditions of a wide population of vehicles using a limited number of WIM devices distributed on the railway network. The evaluation of the axle load conditions is fundamental especially for freight wagons, more subjected to the risk of unbalanced loads which may be extremely dangerous both for the vehicle safety and the infrastructure maintenance. In this work the authors present the development, the simulation and the validation of an innovative WIM algorithm with the aim of estimating the axle loads $\widehat{N}$ of railway vehicles (the axle loads include the wheelset weights). The new estimation algorithm is a general purpose one; theoretically it could be applied by considering as input different kinds of track measurements (rail shear, rail bending, sleepers with sensors, etc.) and could be easily customized for different kinds of signals. In the paper a benchmark case based on rail bending measurements is proposed in which the longitudinal deformations εxx measured on the rail foot through strain sensitive elements are used as input. The considered input is affected by noise and bandwidth limitations and, consequently, is a good benchmark to test the robustness of the new algorithm. To estimate the axle loads, the algorithm approximates the measured physical input through a set of elementary functions calculated by means of a single fictitious load moving on the track. Starting from the set of elementary functions, the measured signal is then reproduced through Least Square Optimization (LSO) techniques: in more detail, the measured signal is considered as a linear combination of the elementary functions, the coefficients of which are the axle loads to be estimated. Authors have also developed a physical model of the railway track. The model consists of the planar FEM (finite elements method) model of the infrastructure and of the two-dimensional (2D) multibody model of the vehicle (the effects of lateral dynamics are treated as disturbances) and takes into account both the coupling between adjacent loads moving on the track and the vehicle dynamics. The physical model of the track and the innovative WIM algorithm (both considering possible measurement errors) have been validated by means of the experimental data kindly provided by Ansaldo STS and have been implemented in the Matlab and Comsol Multiphysics environments. In particular the model of the railway track has been developed expressly to test the WIM algorithm with a suitable simulation campaign when experimental data are not available; in other words it provides simulated inputs to test the WIM algorithm when there are no experimental inputs. 相似文献
One of the main components in ballasted railway track systems is the rail pad. It is installed between the rail and the sleeper
to attenuate wheel/rail interaction loads, preventing the underlying railway sleepers from excessive stress waves. Generally,
the dynamic design of tracks relies on the available data, which are mostly focused on the structural condition at a specific
toe load. Recent findings show that track irregularities could significantly amplify the loads on railway tracks. This phenomenon
gives rise to a concern that the rail pads may experience higher effective preloading than anticipated in the past. On this
ground, this paper highlights the significance of accounting for effects of preloading on dynamic properties of polymeric
rail pads. An innovative test rig for controlling preloads on rail pads has been devised. A non-destructive methodology for
evaluating and monitoring the dynamic properties of the rail pads has been developed based on an instrumented hammer impact
technique and an equivalent single degree-of-freedom system approximation. Based on the impact-excitation responses, some
of the selected rail pads have been tested to determine such modal parameters as dynamic stiffness and damping constants in
the laboratory. The influence of large preloads on dynamic properties of both new and worn rail pads is demonstrated in this
paper. Additionally, the design criteria, which has been used to take into account the influence of the level of preload on
dynamic properties of generic rail pads, are discussed.
Note: The authors’ work in the references can be found electronically via UoW Research Online at URL 相似文献
Summary The paper presents a simple mathematical model which describes the evolution of the vertical profile of a railway track caused
by the load arising from moving vehicles. Owing to the fact that the track ballast is not perfectly elastic, each passage
of a train is accompanied by a residual deformation of the ballast. Being very small, these deformations, however, accumulate
with time. It is shown that an initial imperfection in the vertical profile of the track will either grow or diminish after
each passage. For given track and vehicle, the rate of growth is determined by the characteristic length of the imperfection
and by the velocity of the vehicle.
Received 3 February 2000; accepted for publication 19 July 2000 相似文献
The effect of rail corrugation on the vertical dynamics of railway vehicle coupled with a curved track is investigated in detail with a numerical method when a wheelset is steadily curving. In the calculation of rail corrugation we consider the combination of Kalker‘s rolling contact theory modified, a model of material loss on rail running surface, and a dynamics model of railway vehicle coupled with a curved track. In the establishment of the dynamic model, for simplicity, one fourth of the freight car without lateral motions,namely a wheelset and the equivalent one fourth freight car body above it, is considered. The Euler beam is used to model the rails and the track structure under the rails is replaced with equivalent springs, dampers and mass bodies. The numerical results show the great influence of the rail corrugation on the vibration of the parts of the vehicle and the track, and the some characters of rail corrugation in development. 相似文献