Wheel-rail Lateral Force Research Articles

Running safety evaluation of high-speed train subject to the impact of floating ice collision on bridge piers

In Northeast China and the areas along Sichuan-Tibet railway, collision between floating ice and piers of railway bridges seriously threatens the train operation safety. The safety of high-speed train running on the bridge subject to the impact of floating ice collision is rarely assessed considering the spatial interaction of the train-track-bridge-ice system. To evaluate the running safety and ride comfort of trains and the structural stability of railway bridges under the collision between floating ices and piers, a train-track-bridge (TTB) dynamic interaction model considering the impact of floating ice is established. Using the refined finite element model, the collision process of floating ice on bridge pier is simulated, and the impact loads are employed as the excitation input of the TTB dynamics model. Taking a 5 × 32 m simply-supported bridges as a case study, the influence of bridge structural parameters on the floating ice collision system is investigated, and then the dynamic responses of the TTB system induced by the floating ice impact loads are analyzed in detail. Finally, the effect of the ice impact loads on the running safety of the high-speed train is revealed. Results show that under the floating ice impact loads, the angle of the pier sharp-nose (APSN) and lateral stiffness of foundations are the key parameters that influence the dynamic responses of the bridge, and an improperly small lateral stiffness of foundation would lead to an instability of bridge structure. The influence of ice impact loads on the dynamic responses of the train is remarkable. The lateral vibration acceleration, derailment factor and lateral wheel rail force caused by the ice impact loads are all greater than those caused by the track irregularity, while the wheel unloading rate is slightly smaller. In addition, the running speed of train is also closely related to the running safety and ride comfort when the collision occurs. When the train speed exceeds 400 km/h, the train passing through the bridge would have the possibility of derailment.

Measurement of wheel-rail lateral force using shear strain of wheel web in railway vehicle (Comparison with a conventional bending based method under wheel rotating condition)

Measurement of wheel-rail lateral force using shear strain of wheel web in railway vehicle (Comparison with a conventional bending based method under wheel rotating condition)

Development and application of a calculation method for the equivalent conicity in high-speed turnout Zones

ABSTRACT Equivalent conicity is an equivalent mean parameter for reflecting the effects of lateral wheel-rail forces on passenger comfort on trains. Based on the asymmetry of the variable cross-section rails in the turnout zone, this paper views the equivalent conicity of a wheelset in the turnout zone as an equivalent conicity of a wheelset in which the wheels match all constant-section asymmetrical rails. A calculation method is established for the equivalent conicity of the turnout zone according to the hunting motion wavelength formula of wheelsets; considering the Rolling Radius Difference (RRD) curve of several ‘zero-crossings’, the principle of minimum gravitational stiffness is used as reference for determining the point ye at which the equivalent conicity of a large lateral displacement is calculated. For fluctuating RRD, the equivalent conicity is calculated using the zoning method; the paper also proposes to evaluate wheel-rail contact geometry in the turnout zone based on the nominal equivalent conicity of the most probable lateral displacement of the wheelsets. Using the matching of wheelsets of different service lengths and the No.18 turnout switch zone as an example, this paper studies the effects of a changing wheel profile on the equivalent conicity of the turnout zone.

Artificial neural networks applied to the measurement of lateral wheel-rail contact force: A comparison with a harmonic cancellation method

This paper presents a method for the experimental measurement of the lateral wheel-rail contact force based on Artificial Neural Networks (ANN). It is intended to demonstrate how an Artificial Intelligence (AI) method proves to be a valid alternative to other approaches based on sophisticated mathematical models when it is applied to the wheel-rail contact force measurement problem. This manuscript addresses the problem from a computational and experimental approach. The artificial intelligence algorithm has been experimentally tested in a real scenario using a 1:10 instrumented scaled railway vehicle equipped with a dynamometric wheelset running on a 5-inch-wide track. The obtained results show that the ANN approach is an easy and computationally efficient method to measure the applied lateral force on the instrumented wheel that requires the use of fewer sensors.

Research on Wheel Rail Wear for a 140 t Open Type Hot Metal Car

To maintain the safety of an open-type hot-metal car and to reduce wheel-rail wear during transportation, simulation models of the main components of such car were built using Pro/E software and then tested. In particular, the Pro/E models were imported into ADAMS/Rail for assembly and then used to construct a complete hot-metal car dynamic model. Locomotive wheel-rail attack angle, wheel-rail lateral force, and wear index were used as evaluation parameters during the simulation to analyze the effects of bogie parameter, rail parameter, and speed of the hot-metal car on wheel-rail wear. An improvement scheme for reducing wheel-rail wear was proposed based on the result of the dynamic simulation, wherein wheel-rail wear and curving performance were analyzed and compared. The simulation provided an important reference for evaluating and improving the dynamic performance of the hot-metal car. The applied effect showed that the improvement scheme is effective.

Testing of modified primary stiffness for heavy-haul locomotives operating on sharper-radius curves

For the typical wheelset drive subsystem with axle-suspended motor, the coupled vibration differential equations of wheelset and axle hung motor are derived. The mechanical model of traction rod is established. The subsystems are integrated into a whole locomotive-track coupled dynamic model which is verified from the aspects of load transfer and curving negotiation performance. To reduce the wheel–rail dynamic interaction of six-axle heavy-haul locomotive passing through curves in old existing lines, the parametric optimization flow of primary rubber joint is presented. The stiffness of 12 new rubber joints equipped in drawbars is tested and the stiffness dispersions are investigated. The research results show that, for a single rubber joint, the maximum and minimum values of radial stiffness can, respectively, increase and reduce by 16.2% and 33% with respect to the test mean value. For the assembled axle-box with upper and lower drawbars, the test longitudinal and lateral stiffness increase by 18% and 46%, respectively, relative to the designed values. A distinct dispersion phenomenon in the stiffness distributions of rubber samples is found. By combining with the numerical simulation results, the primary longitudinal stiffness is optimized from 199 MN/m to 52 MN/m, as the lateral stiffness changes from 6.89 MN/m to 2.6 MN/m. The final running test indicates that the optimized parameters can reduce the wheel–rail lateral force by 12% in the 300 m radius curve. The ride comfort could still keep in the same level, and the running stability has not been deteriorated.

Safety analysis of high speed trains under cross winds using indirect wheel-rail force measuring method

For several years the China railway has been investigating the safety risk of passenger cars subjected to cross winds in the LX railway lines. In this paper, an indirect method for wheel-rail force measurement is proposed. By analyzing the forces exerted on the wheelset, the wheel axle lateral force and wheel-rail vertical forces can be derived from the suspension forces and inertia forces. Since it is difficult to separate the wheel-rail lateral forces at two sides of the wheelset, the union safety domain based on the wheelset derailment coefficient and wheel unloading ratio is applied to assess the running safety of the train. The field test of a high speed train travelling in the wind area of the LX high speed railway line was carried out. The identified wheel-rail forces based on the indirect method were compared with that of the instrumented wheelset. The measured wheel-rail forces are analysed to evaluate the running safety of train under cross winds. The derailment evaluation based on union safety domain is compared with the traditional criterion. This indirect method is finally applied to the long-term safety monitoring of high speed trains in operations.

Dynamic analysis of coupled train–track–bridge system subjected to debris flow impact

With the increasing popularity of high-speed railway, more and more bridges are being constructed in Western China where debris flows are very common. A debris flow with moderate intensity may endanger a high-speed train traveling on a bridge, since its direct impact leads to adverse dynamic responses of the bridge and the track structure. In order to address this issue, a dynamic analysis model is established for studying vibrations of coupled train–track–bridge system subjected to debris flow impact, in which a model of debris flow impact load in time domain is proposed and applied on bridge piers as external excitation. In addition, a six-span simply supported box girder bridge is considered as a case study. The dynamic responses of the bridge and the running safety indices such as derailment factor, offload factor, and lateral wheel–rail force of the train are investigated. Some influencing factors are then discussed based on parametric studies. The results show that both bridge responses and running safety indices are greatly amplified due to debris flow impact loads as compared with that without debris flow impact. With respect to the debris flow impact load, the boulder collision has a more negative impact on the dynamic responses of the bridge and train than the dynamic slurry pressure. Both the debris flow impact intensity and train speed determine the running safety indices, and the debris flow occurrence time should be also carefully considered to investigate the worst scenario.

Dynamic performance of high-speed train passing windbreak breach under unsteady crosswind

ABSTRACTField test and computational fluid dynamics (CFD) method are conducted to investigate the safety of high-speed train under unsteady crosswind. Wheel–rail forces of high-speed train passing a breach between two windbreaks under strong crosswind are measured in a field test. The derailment coefficient of first wheelset of front car at the windward side reaches the allowable value. Meanwhile, the left and right of lateral wheel–rail force are in the opposite direction. This kind of phenomenon has not been tested before. Therefore, CFD and multi-body simulations are performed in order to study the phenomena. Good agreement is obtained between the simulation results and the experimental data. It is concluded that the sudden increase of transient aerodynamic loads, when the train passing the breach, is the root of this phenomenon; after running along the same direction as carbody and bogie run along the opposite direction during the high-speed train passing the windbreak breach; larger opposite longitudinal creeping forces of first wheelset compel the first wheelset to yaw toward the windward side; meanwhile, larger lateral wheel–rail forces compel the first wheelset to run toward the windward side rail; the left and right lateral wheel–rail forces become opposite because the right wheel impacts the windward side rail.

The mechanism for the coupler and draft gear and its influence on safety during a train collision

ABSTRACTA mechanical model of the coupler and draft gear was established to study the mechanism during an intercity train collision. The model includes four rigid bodies, one spherical joint, two nonlinear torsion spring units and two nonlinear hysteresis units. Simulation and test results show that the axial characteristics of the model are reasonable and the model can reasonably simulate the pitching movement of the coupler. The influence of the coupler and draft gear on the collision behaviour of the train is analysed considering a four-section intercity train. The results show that during the collision process, the amount of compression of the middle coupler is an important factor influencing the pitching deflection angle. The pitching motion posture of the coupler changes with the initial pitching deflection angle, but the initial pitching deflection angle has little effect on its yawing deflection angle. When the pitching angle of the middle coupler is elevated, as the elevation angle increases, the derailment risk of the ‘A’ end bogie of the previous vehicle increases, whereas the risk of derailment of the ‘B’ end bogie of the subsequent vehicle decreases. When the pitching angle of the middle coupler is depressed, the derailment trends for the front and rear bogies exhibit the opposite trend from that of the elevation angle. As the train collision speed increases, the pitching motion of the middle coupler is limited to forcing a yawing motion, causing the yawing deflection angle to increase sharply, which causes the wheel–rail lateral force to increase rapidly. From this, the derailment risk of the bogie increases, which further causes large displacement lateral buckling of the train. An anti-lateral buckling device can limit the yawing deflection angle of the middle coupler, preventing lateral buckling from large displacement and decreasing the risk of derailment.

Numerical investigation on wheel-turnout rail dynamic interaction excited by wheel diameter difference in high-speed railway

The wheel-rail relationship in turnout is more complicated than that in ordinary track. Profile wear and machining errors of the wheelset cause deviations of the rolling radius on different wheels. Therefore, wheelsets move to the direction of smaller diameter wheels in search of a new stable state and to change the condition before entering the turnout. The main aim of the present work is to examine the wheel-turnout rail dynamic interaction combined with the static contact behaviour. Calculations are performed on a high-speed vehicle CRH2 and the No. 12 turnout of the passenger dedicated line. The wheel-turnout contact geometric relationship and normal contact behaviour under wheel diameter difference are assessed by the trace principle and finite element method. A high-speed vehicle-turnout coupling dynamic model is established based on SIMPACK software to analyse the wheel-rail dynamic interaction, riding comfort, and wear. Both the wheel diameter amplitudes and distribution patterns are accounted for. The simulation shows that wheel diameter difference can greatly disturb the positions’ variation of wheel-rail contact points and affect the normal contact behaviour on switch rails by changing the load transition position. The effect of wheel diameter difference on wheel-turnout rail dynamic interaction can be divided into three according to its amplitude: when the wheel diameter difference is within 0–1.5 mm, the wheel flange comes into contact with the switch rail in advance, causing a rapidly increased lateral wheel-rail force; when it is within 1.5–2.5 mm, trains are subject to instability under equivalent in-phase wheel diameter difference; when it is larger than 2.5 mm, the continuous flange-switch rail contact helps strengthen the vehicle stability, but increases the wheel-rail wear. It is recommended to control the wheel diameter difference to within 2.5 mm but limit it to 2 mm if it is distributed in-phase.

Optimization of Rail Profiles to Improve Vehicle Running Stability in Switch Panel of High-Speed Railway Turnouts

A method for optimizing rail profiles to improve vehicle running stability in switch panel of high-speed railway turnouts is proposed in this paper. The stock rail profiles are optimized to decrease the rolling radii difference (RRD). Such characteristics are defined through given rail profiles, and the target rolling radii difference is defined as a function of lateral displacements of wheel set. The improved sequential quadratic programming (SQP) method is used to generate a sequence of improving profiles leading to the optimum one. The wheel-rail contact geometry and train-turnout dynamic interaction of the optimized profiles and those of nominal profiles are calculated for comparison. Without lateral displacement of wheel set, the maximum RRD in relation to a nominal profile will be kept within 0.5 mm–1 mm, while that in relation to an optimized profile will be kept within 0.3 mm–0.5 mm. For the facing and trailing move of vehicle passing the switch panel in the through route, the lateral wheel-rail contact force is decreased by 34.0% and 29.9%, respectively, the lateral acceleration of car body is decreased by 41.9% and 40.7%, respectively, and the optimized profile will not greatly influence the vertical wheel-rail contact force. The proposed method works efficiently and the results prove to be quite reasonable.

Temperature effect on service performance of high-speed railway concrete bridges

Non-uniform temperature fields induced by time-varying solar position and heat exchange are of great significance for the bridge safety. The accurate identifications of these changes are necessary to avoid unexpected deformations and the loss of service performance. This article presents a numerical approach to determine temperature effects on train–bridge-coupled dynamics. Heat flux density of different components of a 32-m simply supported concrete bridge on high-speed railway is calculated, in which a section segmentation method is adopted for simplifications of boundary conditions. Based on heat–stress-coupled technology, temperature fields and deformation fields of the bridge are then computed via finite element analysis. Combining track irregularities and its thermal deformation as external excitations, the train–bridge-coupled analysis is solved by an inter-system iteration method. Dynamic responses of bridge and train are compared to those obtained neglecting the temperature effect. Comparative studies illustrate that temperature effect has major impacts on the bridge displacement due to the increase in low-frequency components of excitations. For the train, lateral responses are more obvious. Maximum derail factor and lateral wheel–rail force occur when the train leaves from the bridge.

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

The wheel–rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel–rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel–rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel–rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of railway vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel–rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel–rail vertical force. In addition, use of the method to determine the high-frequency wheel–rail interaction forces reveals that it is possible to identify the high-frequency wheel–rail forces through the accelerations on the axle box.

Dynamic simulation and safety evaluation of high-speed trains meeting in open air

Dynamic responses of a carriage under excitation with the German high-speed low-interference track spectrum together with the air pressure pulse generated as high-speed trains passing each other are investigated with a multi-body dynamics method. The variations of degrees of freedom (DOFs: horizontal movement, roll angle, and yaw angle), the lateral wheel-rail force, the derailment coefficient, and the rate of wheel load reduction with time when two carriages meet in open air are obtained and compared with the results of a single train travelling at specified speeds. Results show that the rate of wheel load reduction increases with the increase of train speed and meets some safety standard at a certain speed, but exceeding the value of the rate of wheel load reduction does not necessarily mean derailment. The evaluation standard of the rate of wheel load reduction is somewhat conservative and may be loosened. The pressure pulse has significant effects on the train DOFs, and the evaluations of these safety indexes are strongly suggested in practice. The pressure pulse has a limited effect on the derailment coefficient and the lateral wheel-rail force, and, thus, their further evaluations may be not necessary. The dynamic behaviors of the train’s degrees of freedom (horizontal movement, roll angle and yaw angle), the lateral wheel-rail force, the derailment coefficient, and the rate of wheel load reduction when two high-speed trains meet in open air are investigated with a multi-body dynamics method. The pressure pulse has a limited effect on the derailment coefficient and the lateral wheel-rail force, but it has significant effects on the train’s degrees of freedom, for which evaluations are strongly suggested in practice.

Assessment of the curving performance of heavy haul trains under braking conditions

To study the curving performance of trains, 1D and 3D dynamic models of trains were built using numerical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3D model included three complicated wagons for which longitudinal, lateral, and vertical degrees of freedom were considered. Combined with the calculated results from the 1D model under braking conditions, the behavior of draft gears and brake shoes were added to the 3D model. The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions. The results indicated the following: when a train brakes on a curved track, the wheel-rail lateral force and derailment factor are greater than under idling conditions. Because the yawing movement of the wheelset is limited by brake shoes, the zone of wheel contact along the wheel tread is wider than under idling conditions. Furthermore, as the curvature becomes tighter, the traction ratio shows a nonlinear increasing trend, whether under idling or braking conditions. By increasing the brake shoe pressure, train steering becomes more difficult.

Effects of Track Elasticity on Wheel-Rail Dynamic Performance of Heavy Haul Railway

Two vehicle-track dynamics models on heavy haul railway are established in two conditions of rigid track and elastic track. And the impact of track elasticity on the wheel-rail dynamics performance was analyzed using models. The results show that the critical speed of heavy vehicles and wheel-rail dynamic indexes, such as wheel-rail lateral force and wheel-rail vertical force decreased on elastic track compared with rigid track. However, other dynamic indexes, including derailment coefficient and lateral displacement of wheelsets increased on elastic track. And the wheel-rail wear indexes are some differences on two tracks.

Dynamics of high-speed train in crosswinds based on an air-train-track interaction model

A numerical model for analyzing airtraintrack interaction is proposed to investigate the dynamic behavior of a high-speed train running on a track in crosswinds. The model is composed of a traintrack interaction model and a trainair interaction model. The traintrack interaction model is built on the basis of the vehicletrack coupled dynamics theory. The trainair interaction model is developed based on the train aerodynamics, in which the Arbitrary LagrangianEulerian (ALE) method is employed to deal with the dynamic boundary between the train and the air. Based on the airtraintrack model, characteristics of flow structure around a high-speed train are described and the dynamic behavior of the high-speed train running on track in crosswinds is investigated. Results show that the dynamic indices of the head car are larger than those of other cars in crosswinds. From the viewpoint of dynamic safety evaluation, the running safety of the train in crosswinds is basically controlled by the head car. Compared with the generally used assessment indices of running safety such as the derailment coefficient and the wheel-load reduction ratio, the overturning coefficient will overestimate the running safety of a train on a track under crosswind condition. It is suggested to use the wheel-load reduction ratio and the lateral wheelrail force as the dominant safety assessment indices when high-speed trains run in crosswinds.

Seismic Design Research of Simply Supported Rail-Bridge Based on Running Safety

To explore the practical rail-bridge seismic design methods, dynamic response analysis model of the train-rail-bridge system under seismic loads was established, and the widely used simply supported track-bridge in rail transport was taken for the study. By inputting different intensity and frequency artificial seismic waves to the train-rail-bridge system, the whole history of the vehicles running through the bridge is simulated and the dynamic responses of the bridge and the vehicles are calculated. The influence of train type, seismic intensity and spectral characteristics of the earthquake were analyzed. Taking Japanese traffic safety evaluation indexes including derailment coefficient, wheel offload rate and lateral wheel-rail force as evaluation criteria, the allowed lateral bridge displacement limits and acceleration limits that ensuring train running safety under earthquake were obtained, and the bridge vibration limit curve was drawn. Using Lagrange interpolation method, the mathematical expression of the curve was worked out, which can provide a reference to rail-bridge aseismic design.

Multiobjective Optimization of CRH3 EMU Wheel Profile

The wheel-rail wear problems inherent to railway operation have become increasingly prominent and serious, as they have been proven to be the main factors which affect safety, stability of electric multiple units (EMUs), and wheel-rail maintenance cost. The multiobjective optimization model of CN wheel profile proposed in this study was constructed in effort to reduce the wheel wear of CRH3. Reconstruction of the CN profile based on the nonuniform rational B spline (NURBS) curve theory was designed. Twenty vertical coordinates of the CN profile were selected as design variables, the first wheelset mean wear workand the wheel-rail lateral force were employed as the objective functions, and the wheel geometry, maximal contact pressure, and the derailment coefficient were chosen as the constraint conditions. Particle swarm optimization (PSO) was applied to complete the optimization model combined with the vehicle track coupling dynamics model. Analysis results indicated that the optimized CN-Opti profile possesses more favorable, comprehensive, dynamic, and effective characteristics than the traditional CN profile.