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
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
The dynamic characteristics of a railway vehicle system under unsteady aerodynamic loads are examined in this study. A dynamic analysis model of the railway vehicle considering the influences of aerodynamic loads was established. The model not only considers the forced excitation effect of unsteady aerodynamic loads but also accounts for the effect of unsteady aerodynamic loads on the change of the wheel–rail contact normal forces as well as changes of the wheelset creep coefficients and creep forces/moments. Therefore, this model also considers the influences of unsteady aerodynamic loads on the self-excited vibration characteristics of the vehicle system. The time-history curves, phase trajectory diagrams, Poincaré sections, and Lyapunov exponents of the vehicle system running on a smooth straight track under unsteady aerodynamic loads were determined. The results show that when the critical speed is exceeded, the vehicle system usually performs quasi-periodic motion under unsteady aerodynamic loads, which is significantly different from the periodic motion under steady aerodynamic loads. In different cases, the amplitude and phase of motion are significantly different. The amplitude of the motions can be increased by more than 159%, and the difference of phase can be up to 173°. (The phase is almost reversed.) The dynamic responses of the vehicle system under unsteady aerodynamic loads contain abundant frequency components, including the frequency of the self-excited vibration, the frequency of the forced excitation, and combinations of their integer multiples. The vibration forms corresponding to the main harmonic components under unsteady and steady aerodynamic loads were compared, and the self-excited vibration component of the vehicle system under unsteady aerodynamic loads was identified. The variations in the critical speed with various parameter combinations were computed. The variation range of the critical velocity can reach 73%.
A fracture mechanics based fatigue index for rolling contact fatigue (RCF) initiated at deep (10–25 mm) defects is derived and employed together with a fatigue index for more shallow (4–10 mm) subsurface RCF initiation. Integrated simulations of high-frequency dynamic train–track interaction and prediction of RCF impact are then carried out to evaluate the influence of short-pitch rail corrugation on RCF of railway wheels. Parametric studies are carried out to identify operational conditions likely to generate high RCF impact. Simulation results show how rail corrugation causes a major increase in RCF impact at high-speed operations and that corrugation magnitudes measured in-field are sufficient to generate subsurface initiated RCF. At high speeds the main cause for increased fatigue impact is the increase in dynamic load magnitudes. At lower speeds and higher axle loads also the effect of poor contact geometry will have an influence. 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
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
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
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
Studies were conducted for the establishment of safe axle loads for sugarcane hauling vehicles beyond which detrimental soil compaction would be induced. The treatments involved running a loaded test vehicle in field strips previously chosen at random. Safe loads were established by testing the level of significance of the difference in induced soil compaction between treated and non-treated sections. Working under soil moisture contents of 21.4–27.1% (dry basis), safe axle loads for two 18.4 × 30 tires were found to be 55.6 and 60.0 kN for sandy clay loam and sandy loam soils with initial dry bulk density about 1.434 g/cm3. These corresponded to ground contact pressures of 111 and 120 kPa, respectively. 相似文献
Summary The classical multibody approach in railway vehicle dynamics considers as rolling element a rigid wheelset, for which the geometrical problem associated with the wheel/rail contact and the formulation of the dynamic equations are well known at the present time. New designs of non-conventional bogies led us to develop a new model for independent wheels in which each wheel/rail contact must be treated separately due to the absence of an axle between left and right wheels. This model constitutes an additional feature of the multibody approach for this type of application. The classical multibody formalism is first briefly reviewed and the wheel/rail contact model is then developed in the case of a straight track. The way the model has been extended to curved track is also explained. Finally, numerical results related to classical and non-conventional bogies will be presented before concluding.
Neues Modell des Rad-Gleiskontaktes für unabhängige Räder
Übersicht Die klassische Mehrkörper-Annäherung in der Dynamik der Eisenbahnfahrzeuge betrachtet als Rollelement das steife Achse-Räder-System, dessen geometrisches Problem des Kontaktes zwischen Rad und Gleis sowie dessen Formulierung der dynamischen Gleichungen heutzutage allbekannt sind. Neue Konzepte von unkonventionellen Drehgestellen führte die Autoren zur Entwicklung eines neuen Modells für unabhängige Räder, in welchem aufgrund des Fehlens einer gemeinsamen Achse zwischen linkem und rechtem Rad jeder Rad-Gleis-Kontakt getrennt betrachtet werden soll. Dieses Modell bildet einen zusätzlichen Gesichtspunkt der Mehrkörper-Methode für die Lösung solcher Probleme. Nach kurzer Betrachtung des klassischen Mehrkörper-Formalismus wird ein Modell des Rad-Gleis-Kontaktes für eine gerade Strecke entwickelt. Weiter folgt die Ausweitung des Modells auf ein gekrümmtes Gleis und schließlich werden die numerischen Ergebnisse für klassische und nicht-konventionelle Drehgestelle vorgelegt.
This paper describes the results of a study of applying the physics-based, computer-aided method – the Nepean Tracked Vehicle Performance Model (NTVPM), originally developed for evaluating the mobility of large, heavy tracked vehicles, to predicting the performance of a small, lightweight track system on sandy soil. The objective is to examine the applicability of NTVPM to predicting the cross-country performance of small, lightweight tracked vehicles on deformable terrain. The performance of the track system predicted by NTVPM is compared with experimental data obtained in a laboratory soil bin by the Robotic Mobility Group, Massachusetts Institute of Technology. It is shown that the correlation between the tractive performance predicted by NTVPM and that measured is reasonably close, as indicated by the values of the coefficient of correlation, coefficient of determination, root mean squared deviation, and coefficient of variation. The results of this study provide evidence for supporting the view that physics-based methods, such as NTVPM, that are developed on the understanding of the physical nature and detailed analysis of vehicle–terrain interaction, are applicable to large, heavy, as well as small, lightweight vehicles, provided that appropriate terrain data are used as input. 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
A calculation model is put forward to analyze the effect of a scratch on the running surface of a curved rail on initiation and growth of plastic deformation induced rail corrugation when a wheelset is steadily and repeatedly curving. The numerical method considers a combination of Carter’s two-dimensional contact theory, a two-dimensional elastic–plastic finite element model and a vertical dynamics model of railway vehicle coupled with a curved track. A concept of feedback between the corrugation development and the vertical coupling dynamics of the wheelset and track is involved. The cyclic ratchetting effect of the rail material under repeated contact loadings is taken into account. The numerical results indicate that when a vehicle runs on rails with a scratch the contact vibration between the wheel and rail occurs at large amplitude, and rail corrugation due to plastic deformation initiates and develops. The corrugation has a tendency to move along the running direction and its evolution rate decays as wheelset passages increase. The passing frequencies of the plastic deformation induced corrugation depend on the natural frequencies of the track. The residual stresses stabilize after a limited number of wheelset passages. The residual strains increase at a reduced rate with increasing wheelset passages. 相似文献