Yan Quan Sun

A dynamic model for the vertical interaction of the rail track and wagon system

Abstract With the advent of high-speed trains, there is a renewed interest in the rail track–vehicle interaction studies. As part of an ongoing investigation of the track system optimisation and fatigue of the track components, a dynamic model is developed to examine the vertical interaction of the rail track and the wagon system. Wagon with four wheelsets representing two bogies is modelled as a 10 degree of freedom subsystem, the track is modelled as a four-layer subsystem and the two subsystems are coupled together via the non-linear Hertz contact mechanism. The current model is validated using several field test data and other numerical models reported in the literature by other researchers.

A THREE-DIMENSIONAL MODEL FOR THE LATERAL AND VERTICAL DYNAMICS OF WAGON-TRACK SYSTEMS

Abstract Lateral and vertical dynamics of the wagon and track affects the maintenance and safety of the heavy haul railway operation. With a view to understanding this aspect comprehensively, a three-dimensional wagon-track system dynamics (WTSD) model is developed and presented. The model consists of a full wagon with 37 degrees of freedom (DOF), a four-layer track with discretely supported rails and a wheel-rail interface representing Kalkers creep and Hertzian contact parameters. The model has been validated using two sets of field data: one dealing with vertical impact due to the flat wheel and the other dealing with lateral hunting. The effect of detailed track modelling on lateral hunting is discussed, and the capability of the three-dimensional WTSD model in predicting lateral impact is demonstrated.

Simulated comparisons of wagon coupler systems in heavy haul trains

Abstract Three types of wagon connection coupling systems are evaluated in a train simulation model consisting of 107 vehicles. The three wagon connection coupling systems are auto-couplers with standard draft gears, auto-couplers with draft gears with wedge unlocking features, and the traditional drawhook buffer system. The train is made up of 103 wagons and 4 locomotives. The locomotives are placed in groups of two at the head and mid-train positions. Dynamic response and fatigue damage is compared for a control disturbance on a crest and on a flat track section. The effect of coupling-free travel (slack) is also investigated.

Wagon instability in long trains

Lateral force components and impacts from couplers can adversely affect wagon stability. These issues are significant in longer and heavier trains increasing the risk of wagon rollover, wheel climb, wagon body pitch, bogie pitch and wagon lift-off. Modelling of coupler angles has been added to normal longitudinal train simulation to allow comprehensive study of lateral components of coupler forces. Lateral coupler forces are then combined with centripetal inertia calculations to determine quasi-static lateral forces, quasi-static vertical forces and quasi-static bogie lateral to vertical ratio, allowing the study of stringlining, buckling and wagon rollover risks. The approach taken allows for different rolling stock lengths, overhang and coupling lengths, and allows the study of angles occurring in transitions. Wagon body and bogie pitch are also studied with enhancements added to previous modelling to allow the study of wagon lift-off.

Design and Simulation of Rail Vehicles

The fields of rail vehicle design, maintenance, and modification, as well as performance issues related to these types of vehicles, are examined in this text. Rail vehicle design issues and dynamic responses are analyzed, design and features of rail vehicles are described, and methods that address the operational conditions of this complex system are introduced. Both non-powered and powered rail vehicles are a focus - passenger and freight rolling stock, locomotives, and self-powered vehicles used for public transportation. Problems involved in designing and modeling all types of rail vehicles are introduced. Applications of train operations, vehicle dynamics, and track infrastructure maintenance are explored. Fundamentals of locomotive design, longitudinal train dynamics, and multibody dynamics are introduced, and co-simulation techniques are discussed. Recent advances in rail vehicle design are highlighted, and applicable standards and acceptance tests from around the world are contained.

Development of a real-time bogie test rig model based on railway specialised multibody software

The design of mechatronic systems of rail vehicles requires performing verification and validation in the real-time mode. One useful validation instrument is the application of software-in-the-loop, hardware-in-the-loop or processor-in-the-loop simulation approaches. All of these approaches require development of a real-time model of the physical system. In this paper, the investigation of the usage of the model of the locomotives bogie test rig created in Gensys multibody software has been performed and the calculation time for each time step has been analysed. The verification of the possibility of the usage of such an approach for real-time simulation has been made by means of a simple data transferring process between Gensys and Simulink through the TCP/IP interface. The limitations and further development issues for the proposed approach have been discussed in this paper.

Investigation of locomotive multibody modelling issues and results assessment based on the locomotive model acceptance procedure

The acceptable dynamic behaviour of railway locomotives is governed by different standards in different parts of the world. Some standards allow the use of multibody simulation tools (such as VAMPIRE, NUCARS, GENSYS and SIMPACK) in place of physical testing, but generally not for all locomotive tests within each standard. Virtual multibody locomotive models can allow simple analyses, such as for slightly modified and relocated locomotives, to be completed in less time, and lower cost and effort in comparison with physical type testing. Unfortunately, the detailed locomotive model acceptance procedures required to achieve this for locomotive designs do not presently exist. This paper discusses the methodology behind a proposed locomotive model acceptance procedure that is currently intended for Australian freight locomotives, although it can be modified to suit other countries and locomotive types. A review of relevant international standards was first undertaken to determine which tests to include and to draw from international best practice. A few case studies are then given to show how the proposed methodology can be implemented on a heavy haul locomotive model.

Nonlinear three-dimensional wagon–track model for the investigation of rail corrugation initiation on curved track

A nonlinear wagon–track model on curved track has been developed to characterize rail corrugation formation due to self-excitation of the wheel–rail stick–slip process. In this model, wagon movements were described using up to 78 degrees of freedom (DOFs) to model a three-piece freight bogie. Innovatively, the wheelset movements are described using nine DOFs, including torsional and bending modes about the longitudinal and vertical directions. The track modelling is considered as a one-layer structure (two rail beams on discrete spring and damper elements). The wheel sliding after creepage saturation is considered in the wheel–rail interface modelling. Simulation of a case study shows that the frequencies of the wheel stick–slip process are composed of the basic frequency, which might come from the combined effect of sleeper-passing frequency and one-third of the combined torsional and bending frequency of the wheelset, and the double and triple basic frequencies, which form the wavelengths of rail corrugation at different situations.

Adhesion estimation and its implementation for traction control of locomotives

During locomotive movement in traction or braking modes, body weight distribution varies between bogies in different proportions depending on many factors. Each bogie and wheelset thus experiences a different traction coefficient. Locomotive manufacturers introduce traction control system strategies for achieving optimal adhesion allowing for axle weight transfers. Determination of adhesion coefficients to input into traction control systems is a complex and difficult issue. Optimising this task requires solving the problem of how to estimate rail friction condition. This paper describes the algorithm which allows estimation of friction parameters for hauling locomotives, and uses a low computational cost solution based on existing approaches and input signals from sensors. The verification of the algorithm is performed using a co-simulation process between the multibody software and Matlab/Simulink package. Simulation results obtained confirm that the proposed approach is an efficient and practical tool that can be recommended for implementation for locomotive traction control systems.

The Calculation of Wheel Impact Force Due to the Interaction between Vehicle and a Turnout

It is known that railway turnouts demand more maintenance than other parts of the railway track network because of large impact loads generated by the variation of wheel-rail contact conditions along the turnout and through the crossing. A method using VAMPIRE® modelling to determine the wheel impact forces due to passing turnout has been developed and presented in this article. The simulation shows that both turnout curve and crossing have significant effect on the wheel impact forces; the vertical impact forces from the turnout case are not significantly different from the wheels travelling straight through.