Jia-yang Xiong

Bio: Jia-yang Xiong is an academic researcher from Southwest Jiaotong University. The author has contributed to research in topics: Track (rail transport) & Degrees of freedom (mechanics). The author has an hindex of 5, co-authored 6 publications receiving 137 citations.

A 3D model for coupling dynamics analysis of high-speed train/track system

Abstract: A 3D dynamic model of a high-speed train coupled with a flexible ballast track is developed and is presented in this study. In this model, each vehicle is modeled as a 42 degrees of freedom multi-body system, which takes into consideration the nonlinear dynamic characteristics of the suspensions. A detailed inter-vehicle connection model including nonlinear couplers and inter-vehicle dampers, and the linear tight-lock vestibule diaphragm is established to simulate the effect of the end connections of neighboring vehicles on dynamic behavior. The track is modeled as a traditional three-layer discrete elastic support model. The rails are assumed to be Timoshenko beams supported by discrete sleepers. Each sleeper is treated as an Euler beam and the ballast bed is replaced by equivalent rigid ballast bodies. The reliability of the present model is then validated through a detailed numerical simulation comparison with the commercial software SIMPACK, with the effect of the track flexibility on the train/track interaction being analyzed simultaneously. The proposed model is finally applied to investigate the difference between dynamic performances obtained using the entire-train/track model (TTM) and the single-vehicle/track model (VTM). Several key dynamic performances, including vibration frequency response, ride comfort, and curving performance, calculated by the two types of dynamic models are compared and discussed. The numerical results show that there is a significant difference between the dynamic behaviors obtained by VTM and TTM, and that inter-vehicle connections have an important influence on the dynamic behavior of high-speed vehicles.

Study on safety boundary for high-speed train running in severe environments

Abstract: This article reviews some important published papers regarding the discussions on the mechanism and the modelling of trains operating in severe environments which are originally defined. A few important derailment criteria are briefly discussed. A study strategy of the safety operation boundaries of high-speed trains operating in the severe environments is first put forward. In the strategy, the safety operation boundaries are defined as a number of separatrices which clearly indicate the safety operation area, warning area and derailment occurring area of a high-speed vehicle in operation. The defined separatrices are the limit surface functions of the key factors influencing the vehicle dynamic behaviour and its derailment. They are found through numerical simulation by using an advanced dynamics model for vehicle/track interaction and the derailment criteria. In order to fully understand the present strategy, a detailed numerical example of a high-speed vehicle passing over a buckled track is discussed...

Effect of the first two wheelset bending modes on wheel-rail contact behavior

Abstract: The objective of this paper is to develop a new wheel–rail contact model, which is suitable for considering the effect of wheelset bending deformation on wheel–rail contact behavior at high speeds. Dummies of the two rigid half wheelsets are introduced to describe the spacial positions of the wheels of the deformed wheelset. In modeling the flexible wheelset, the first two wheelset bending modes are considered. Based on the modal synthesis method, these mode values of the wheelset axle are used to solve the motion equations of the flexible wheelset axle modeled as an Euler–Bernoulli beam. The wheel is assumed to be rigid and always perpendicular to the deformed axle at the wheel center. In the vehicle model, two bogies and one car body are modeled as lumped masses. Spring–damper elements are adopted to model the primary and secondary suspension systems. The ballasted track is modeled as a triple-layer discrete elastic supported model. Two high-speed vehicle–track models, one considering rigid wheelset models and the other considering flexible wheelset models, are used to analyze the differences of the numerical results of the two models in both frequency and time domains. In the simulation, a random high-speed railway track irregularity is used as wheel–rail excitations. Wheel–rail forces are calculated and analyzed in the time and frequency domains. The results clarify that this new contact model can characterize very well the influence of the first two bending modes of the wheelset on contact behavior.

Study on the safety of operating high-speed railway vehicles subjected to crosswinds

Abstract: A coupled vehicle-track dynamic model is put forward for use in investigating the safety effects of crosswinds on the operation of a high-speed railway vehicle. In this model, the vehicle is modeled as a nonlinear multi-body system, and the ballasted track is modeled as a three-layer discrete elastic support system. The steady aerodynamic forces caused by crosswinds are modeled as ramp-shaped external forces being exerted on the vehicle body. This model was used in a numerical analysis of the dynamic response and dynamic derailment mechanisms of high-speed vehicles subjected to strong crosswinds. The effects of the crosswind speeds, crosswind attack angle, and vehicle speed on the operational safety of the vehicle were examined. The operational safety boundaries of a high-speed vehicle subjected to crosswinds were determined. The numerical results obtained indicate that crosswinds at attack angles of 75° to 90° with respect to the forward direction of the vehicle have a great influence on the safety of operating high-speed railway vehicles. The wheelset unloading limit, which determines the position of the warning boundary dividing the safe operating area and the warning area, is the most conservative, i.e., the safest, criterion to use in assessing the high-speed operational safety of vehicles in crosswinds.

A three-dimensional model for coupling dynamics analysis of high speed train-track system *

Abstract: A three-dimensional dynamic model of a high-speed train coupled with a flexible ballast track was developed and is presented in this paper. In the model, each vehicle was modeled as a 42 degrees of freedom multi-body system, which takes into consideration the nonlinear dynamic characteristics of the suspensions. A detailed inter-vehicle connection model including nonlinear couplers and inter-vehicle dampers, and the linear tight-lock vestibule diaphragm is established to simulate the effect of the end connections of neighboring vehicles on dynamic behavior. The track is modeled as a traditional 3-layer discrete elastic support model. The rails are assumed to be Timoshenko beams supported by discrete sleepers. Each sleeper is treated as an Euler beam and the ballast bed is replaced by equivalent rigid ballast bodies. The reliability of the present model was then validated through a detailed numerical simulation comparison with the commercial software SIMPACK, with the effect of the track flexi- bility on the train/track interaction being analyzed simultaneously. The proposed model was finally applied to investigate the difference between dynamic performances obtained by using the entire-train/track model (TTM) and the single-vehicle/track model (VTM). Several key dynamic performances, including vibration frequency response, ride comfort, curving performance, calculated by the two types of dynamic models are compared and discussed in detail. The numerical results show that there is a significant difference between the dynamic behaviors obtained by VTM and TTM, and that inter-vehicle connections have an important influence on the dynamic behavior of high-speed vehicles.

Prognostics and health management for maintenance practitioners - Review, implementation and tools evaluation

Abstract: In literature, prognostics and health management (PHM) systems have been studied by many researchers from many different engineering fields to increase system reliability, availability, safety and to reduce the maintenance cost of engineering assets. Many works conducted in PHM research concentrate on designing robust and accurate models to assess the health state of components for particular applications to support decision making. Models which involve mathematical interpretations, assumptions and approximations make PHM hard to understand and implement in real world applications, especially by maintenance practitioners in industry. Prior knowledge to implement PHM in complex systems is crucial to building highly reliable systems. To fill this gap and motivate industry practitioners, this paper attempts to provide a comprehensive review on PHM domain and discusses important issues on uncertainty quantification, implementation aspects next to prognostics feature and tool evaluation. In this paper, PHM implementation steps consists of; (1) critical component analysis, (2) appropriate sensor selection for condition monitoring (CM), (3) prognostics feature evaluation under data analysis and (4) prognostics methodology and tool evaluation matrices derived from PHM literature. Besides PHM implementation aspects, this paper also reviews previous and on-going research in high-speed train bogies to highlight problems faced in train industry and emphasize the significance of PHM for further investigations.

Modeling and analyses of a connected multi-car train system employing the inerter

Abstract: This article develops the model of a connected multi-car train system and discusses the improvement of stability and performance by the inerter. The inerter is a genuine two-terminal element, whose...

Polygonisation of railway wheels: a critical review

Abstract: Polygonisation is a common nonuniform wear phenomenon occurring in railway vehicle wheels and has a severe impact on the vehicle–track system, ride comfort, and lineside residents. This paper first summarizes periodic defects of the wheels, including wheel polygonisation and wheel corrugation, occurring in railways worldwide. Thereafter, the effects of wheel polygonisation on the wheel–rail interaction, noise and vibration, and fatigue failure of the vehicle and track components are reviewed. Based on the different causes, the formation mechanisms of periodic wheel defects are classified into three categories: (1) initial defects of wheels, (2) natural vibration of the vehicle–track system, and (3) thermoelastic instability. In addition, the simulation methods of wheel polygonisation evolution and countermeasures to mitigate wheel polygonisation are presented. Emphasis is given to the characteristics, effects, causes, and solutions of wheel polygonisation in metro vehicles, locomotives, and high-speed trains in China. Finally, the guidance is provided on further understanding the formation mechanisms, monitoring technology, and maintenance criterion of wheel polygonisation.

A 3D model for coupling dynamics analysis of high-speed train/track system

Abstract: A 3D dynamic model of a high-speed train coupled with a flexible ballast track is developed and is presented in this study. In this model, each vehicle is modeled as a 42 degrees of freedom multi-body system, which takes into consideration the nonlinear dynamic characteristics of the suspensions. A detailed inter-vehicle connection model including nonlinear couplers and inter-vehicle dampers, and the linear tight-lock vestibule diaphragm is established to simulate the effect of the end connections of neighboring vehicles on dynamic behavior. The track is modeled as a traditional three-layer discrete elastic support model. The rails are assumed to be Timoshenko beams supported by discrete sleepers. Each sleeper is treated as an Euler beam and the ballast bed is replaced by equivalent rigid ballast bodies. The reliability of the present model is then validated through a detailed numerical simulation comparison with the commercial software SIMPACK, with the effect of the track flexibility on the train/track interaction being analyzed simultaneously. The proposed model is finally applied to investigate the difference between dynamic performances obtained using the entire-train/track model (TTM) and the single-vehicle/track model (VTM). Several key dynamic performances, including vibration frequency response, ride comfort, and curving performance, calculated by the two types of dynamic models are compared and discussed. The numerical results show that there is a significant difference between the dynamic behaviors obtained by VTM and TTM, and that inter-vehicle connections have an important influence on the dynamic behavior of high-speed vehicles.

Key problems faced in high-speed train operation

Abstract: This paper discusses some key problems faced in high-speed train operation. These problems include: wheel tread concave wear causing the lateral oscillation of the train in operation, wheel roundness higher-order polygonal wear leading to fierce vertical vibration of wheel/rail and abnormal vibration noise of the coach interior of the train thus causing loosening and cracking of the train bogie parts, short pitch rail corrugation generation on the part of the track, fracture of cushion layer and road base fracture of the track, and increased noise inside and outside the train. At present, the mechanism of the occurrence and development of these phenomena is still not fully understood. This paper briefly reviews the related research on these problems in China and abroad, including many important recent papers and the articles published in this special issue. They make outstanding contributions to solving these problems, and include important work on train-track coupling large system theory, the relationship theory and technique of wheel/rail, and the vibration-noise reduction technology of the train.