Measured dynamic load distribution within the in situ axlebox bearing of high-speed trains under polygonal wheel–rail excitation

The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input.

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

Based on the discrete time method, an effective movement control model is designed for a group of high- speed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains＇ movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and reseheduling trains on the rail network.

Running safety assessment method of trains under seismic conditions based on the derailment risk domain

The accurate assessment of running safety during earthquakes is of significant importance for ensuring the safety of railway lines.Currently,assessment methods based on a single index suffer from issues such as misjudgment of operational safety and difficulty in evaluating operational margin,making them unsuitable for assessing train safety during earthquakes.Therefore,in order to propose an effective evaluation method for the running safety of trains during earthquakes,this study employs three indexes,namely lateral displacement of the wheel–rail contact point,wheel unloading rate,and wheel lift,to describe the lateral and vertical contact states between the wheel and rail.The corresponding evolution characteristics of the wheel–rail contact states are determined,and the derailment forms under different frequency components of seismic motion are identified through dynamic numerical simulations of the train–track coupled system under sine excitation.The variations in the wheel–rail contact states during the transition from a safe state to the critical state of derailment are analyzed,thereby constructing the evolutionary path of train derailment and seismic derailment risk domain.Lastly,the wheel–rail contact and derailment states under seismic conditions are analyzed,thus verifying the effectiveness of the evaluation method for assessing running safety under earthquakes proposed in this study.The results indicate that the assessment method based on the derailment risk domain accurately and comprehensively reflects the wheel–rail contact states under seismic conditions.It successfully determines the forms of train derailment,the risk levels of derailment,and the evolutionary paths of derailment risk.

Minimum Curve Radii for High-Speed Trains, Including the Gyroscopic Moments of the Wheels

This paper studies the title problem including an analysis of the gyroscopic effects of the wheels of a rail-car travelling at high-speed around a level, horizontal curve. The analysis is based upon the fundamental principles of dynamics. The result is a design formula for the minimum curve radius needed to prevent derailment. Aside from the rail car geometric and physical properties, the minimum curve radius depends upon the square the train speed. An illustrative example shows that the wheel gyroscopic effect is destabilizing and additive to the centrifugal force derailment tendency. From a track design perspective, however, the gyroscopic effect is relatively small compared with the centrifugal force effect.

Rail temperature rise characteristics caused by linear eddy current brake of high-speed train

The rail temperature rises when the linear eddy current brake of high-speed train is working, which may lead to a change of rail physical characteristics or an effect on train operations. Therefore, a study concerning the characteristics of rail temperature rise caused by eddy current has its practical necessity. In the research, the working principle of a linear eddy current brake is introduced and its FEA model is established. According to the generation mechanism of eddy current, the theoretical formula of the internal energy which is produced by the eddy current is deduced and the thermal load on the rail is obtained. ANSYS is used to simulate the rail temperature changes under different conditions of thermal loads. The research result shows the main factors which contribute to the rising of rail temperature are the train speed, brake gap and exciting current. The rail temperature rises non-linearly with the in- crease of train speed. The rail temperature rise curve is more sensitive to the exciting current than the air gap. Moreover, the difference stimulated by temperature rising between rails of 60 kg/m and 75 kg/m is presented as well.

Numerical study of wheel–rail adhesion performance of new-concept high-speed trains with aerodynamic wings

Wheel–rail adhesion is a complex tribological problem of wheel–rail rolling contact and is closely related to the operational safety of high-speed trains.A new design concept of high-speed trains was recently proposed with an expectation of a reduction of equivalent weight and total energy consumption by installing aerodynamic wings(aero-wings)on the roof,but it was accompanied by the disadvantage of deteriorating wheel–rail adhesion performance.In this study,a comprehensive multibody dynamics(MBD)model of the high-speed train with predesigned aero-wings is established using the commercial software SIMPACK,in which the real aerodynamic characteristics of the train are taken into account.The available adhesion and adhesion margin are employed to evaluate the wheel–rail adhesion performance.The influences of aero-wing lift,train speed,and contact conditions on the wheel–rail adhesion level are discussed.The results show that the load transfer caused by the action of aerodynamic load and braking torque was the main reason for the inconsistent adhesion condition of four wheelsets.The influences of aero-wing lift and train speed on the wheel–rail adhesion performance are coupled;the available adhesion of both motor car and trailer is negatively correlated with aero-wing lift and train speed under all contact conditions,while the variation law of adhesion margin with train speed shows differences under different contact conditions.When the wheel–rail interface was polluted by a‘third-body medium’such as water and oil,the wheel–rail adhesion performance was dramatically reduced and the wheelset tended to reach adhesion saturation and slide.However,track irregularity had little effect on the adhesion performance and could be ignored to save calculation time.These results are of positive significance for reducing the wheel idling or sliding phenomenon and to ensure the safe operation of high-speed trains with aero-wings.

Wind tunnel tests on aerodynamic characteristics of vehicles on same-storey highway and rail bridge under crosswind

In recent years,the safety and comfort of road vehicles driving on bridges under crosswinds have attracted more attention due to frequent occurrences of wind-induced disasters.This study focuses on a container truck and CRH2 high-speed train as research targets.Wind tunnel experiments are performed to investigate shielding effects of trains on aerodynamic characteristics of trucks.The results show that aerodynamic interference between trains and trucks varies with positions of trains(upstream,downstream)and trucks(upwind,downwind)and numbers of trains.To summarize,whether the train is upstream or downstream of tracks has basically no effect on aerodynamic forces,other than moments,of a truck driving on windward sides of bridges(upwind).In contrast,the presence of trains on the bridge deck has a significant impact on aerodynamic characteristics of a truck driving on leeward sides(downwind)at the same time.The best shielding effect on lateral forces of trucks occurs when the train is located downstream of tracks.Finally,the pressure measuring system shows that only lift forces on trains are affected by trucks,while other forces and moments are primarily affected by adjacent trains.

Dynamic analysis of a high-speed train operating on a curved track with failed fasteners

A high-speed train-track coupling dynamic model is used to investigate the dynamic behavior of a high-speed train operating on a curved track with failed fasteners. The model considers a high-speed train consisting of eight vehicles coupled with a ballasted track. The vehicle is modeled as a multi-body system, and the rail is modeled with a Timoshenko beam resting on the discrete sleepers. The vehicle model considers the effect of the end connections of the neighboring vehicles on the dynamic behavior. The track model takes into account the lateral, vertical, and torsional deformations of the rails and the effect of the discrete sleeper support on the coupling dynamics of the vehicles and the track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. The train model couples with the track model by using a Hertzian contact model for the wheel/rail normal force calculation, and the nonlinear creep theory by Shen et al. (1984) is used for wheel/rail tangent force calculation. In the analysis, a curved track of 7000-m radius with failed fasteners is selected, and the effects of train operational speed and the number of failed fasteners on the dynamic behaviors of the train and the track are investigated in detail. Furthermore, the wheel/rail forces and derailment coefficient and the wheelset loading reduction are analyzed when the high-speed train passes over the curved track with the different number of continuously failed fasteners at different operational speeds. Through the detailed numerical analysis, it is found that the high-speed train can operate normally on the curved track of 7000-m radius at the speeds of 200 km/h to 350 km/h.

Development and validation of a model for predicting wheel wear in high-speed trains

In this paper, we present a comprehensive model for the prediction of the evolution of high-speed train wheel profiles due to wear. The model consists of four modules： a multi-body model implemented with the commercial multi-body software SIMPACK to evaluate the dynamic response of the vehicle and track; a local contact model based on Hertzian theory and a novel method, named FaStrip （Sichani et al., 2016）, to calculate the normal and tangential forces, respectively; a wear model proposed by the University of Sheffield （known as the USFD wear function） to estimate the amount of material removed and its distribution along the wheel profile; and a smoothing and updating strategy. A simulation of the wheel wear of the high-speed train CRH3 in service on the Wuhan-Guangzhou railway line was performed. A virtual railway line based on the statistics of the line was used to represent the entire real track. The model was validated using the wheel wear data of the CRH3 operating on the Wuhan- Guangzhou line, monitored by the authors＇ research group. The results of the predictions and measurements were in good agreement.

Dynamic performance of vehicle in high-speed freight EMU equipped with four double-axle bogies

Size and weight limitations mean that ordinary railway vehicles with two double-axle bogies cannot deliver some extremely heavy cargo and products.Thus,a newly designed high-speed freight electric multiple unit(EMU)equipped with two bogie groups each with two double-axle bogies connected by a transition frame is an alternative means of transporting heavy products because of its greater load capacity.However,because it is still in the design stage,its dynamic performance is yet to be researched,something that is urgently required because of the more-complicated structure and more-intensive wheel-rail interactions than those of traditional high-speed railway vehicles.Therefore,to reveal the dynamic performance,this study establishes a three-dimensional dynamic model of a trailer vehicle in a high-speed freight EMU equipped with four double-axle bogies based on the classical theory of vehicle-track coupled dynamics.In this dynamic model,the vertical,horizontal,rolling,pitching,and yaw motions of the major components excited by random irregularities in the track geometry are considered fully.The results indicate that the derailment coefficient and stability index of this vehicle are both at excellent levels for the simulated conditions.The wheel unloading ratio appears to be larger but still within the safety range when the vehicle runs in a straight line,but it is close to or can even exceed the limit value when the vehicle runs at 400 km/h on a specified curved line.

我国铁路现代物流政策形势影响及发展策略研究

铁路现代物流随着我国经济社会的发展不断发展,同时面临国家能源结构优化、产业结构调整、消费结构变化带来的挑战和机遇。在阐述“十三五”以来社会物流发展现状的基础上,通过研究以煤炭为重点的大宗物流,以工业制成品和实物消费品为重点的白货物流政策形势影响,分析未来铁路大宗物资运量逐步下降和铁路白货物流市场空间广阔,从加强社会物流研究、深化煤炭“公转铁”、推动白货“公联铁”、发展集装箱运输、完善铁路场站配套设施等方面,提出我国铁路现代物流发展策略,以更好应对挑战、把握机遇,为铁路现代物流高质量发展提供参考。

高铁货运专列与城市车辆多站点协同的配送模式及路径优化

在高附加值、高时效要求的快递日益激增的需求驱动下,高铁货运专列运营常态化越来越成为可能。由于超大城市快递量多、城市面积大,高铁快运通过单个站点停靠再衔接城市车辆进行快递配送时,快递的高时效性往往得不到有效保障。基于此,创新提出“去配送中心”的“高铁货运专列多站停靠+城市车辆多点协同”越库配送模式,并对该模式的运行条件进行讨论。在考虑高铁货运专列运输时间表、客户服务时间窗等限制条件的基础上,建立高铁货运专列多点协同城市车辆配送路径优化模型。以超大城市上海市为例,对该配送模式的应用进行讨论,设计模拟退火算法进行求解。研究结果表明:“高铁货运专列多站停靠+城市车辆多点协同”的越库配送模式配送成本更低、准时性更高,能够更高效地完成快递配送。

新型高铁列车推进高铁运输与现代物流的融合问题

现代物流已逐渐成为企业创造利润的主要途径,也是企业核心竞争力的具体体现,保障了整个国民经济的高效运行。国民经济的发展对铁路运输业提出了更高、更新的要求。高铁货运具有成本低、耗时短、准时率高等诸多优势,也不像航空货运极易受冰冻雨雪等天气因素的影响,因而实施高速铁路货运是经济社会发展的必然产物,可以大幅提高货物的运输效率,是实现铁路运输与现代物流的融合与发展的关键路径。由于中国庞大的货运需求及铁路自身的限制因素,高铁货物运输存在供需矛盾及自身的结构性矛盾。采用定性及定量分析相结合的方法,从中车公司开发的3X餐货两用车的特性和优势入手,通过定性分析指出该系列动车组是解决现存货物运输问题的有效途径;以京沪高速铁路线为算例,定量地分析后认为在主要高铁线路运行新型餐货两用车预期带来的经济效益。研究结果表明:中车公司研发的3X新型高铁列车的投入运营,不仅在客运方面具有巨大的经济效益,在货运方面也会积极推进高铁运输与现代物流的融合,是适应中国国情及铁路发展前景的铁路产品,能够为社会带来巨大的经济和社会效益。

复杂轮轨接触条件下机车牵引/制动性能分析

不同的轮轨接触条件对轮轨黏着系数影响显著,而轮轨间的黏着特性对列车的牵引和制动性能起着决定性作用。以HXD_(2)双机牵引2000 t货物列车编组为例,建立了列车-轨道垂纵动力学模型,分析了不同坡道和不同轮轨接触条件下机车的黏着特性,并根据黏着特性曲线计算出低黏着条件下机车能够发挥的最大牵引/制动力。结果表明:货物列车以牵引状态匀速通过10‰和20‰坡道时,在冰雪接触状态下会发生车轮空转;通过30‰坡道时,在油态和冰雪接触状态下均会发生车轮空转,此时车轮纵向蠕滑率明显增大,黏着系数降低;低黏着接触条件下的最大牵引/制动力值低于HXD_(2)型机车牵引/制动力限值,并由此给出了在低黏着接触条件下建议采用的牵引/制动特性曲线;在坡度超过10‰时的冰雪接触条件下以及30‰坡道的油态接触条件下,货物列车均无法保持匀速运行。

轨道交通物流运输模式及其可行性探讨

随着电子商务的繁荣发展,城市物流的需求急剧增长,同时城市道路交通拥堵、交通安全、环境污染等问题也随之加剧,利用城市轨道交通承担部分物流服务或许是新的途径。首先,通过分析轨道交通物流可能的4种运输模式,细化各模式基本特征和必要条件,探讨不同模式下轨道交通物流的可行性;其次,从载运量、服务时间范围、运输组织等指标出发,认为客货混编是最有可能的轨道交通物流运输组织模式。研究结果认为,虽然轨道交通物流具有独特优势,但在现有条件下开展轨道交通货运业务仍然存在巨大瓶颈,开行条件尚不成熟。

高铁快运物流运输组织优化研究

高铁快运物流业务是中国国家铁路集团有限公司利用高速铁路运力资源开发的现代物流运输产品,是新的铁路货运业务利润增长点。目前,我国高铁快运物流迅速发展,但在运输组织方面仍存在问题,影响高铁快运货物的输送效率。从列车载运空间、车站货运设施、作业流程规范、运输组织协调和内外部信息集成5个方面入手,分析高铁快运物流运输组织存在问题。基于时效性与安全性2大优化原则,结合现场作业的常见问题,在提高列车载运能力、改造车站货运设施、优化装卸作业流程、加强部门内部协调和提高信息集成水平等方面提出相应的优化对策,以优化高铁快运物流运输组织。

城市轨道交通开展物流配送的可行性及运行模式研究

以轨道交通作为研究对象,借鉴高铁快递的成功运营经验,结合轨道交通与物流配送的系统特征,对轨道交通开展物流配送的可行性进行了分析研究,并提出了客货混编与货运专列两种主要运行模式,对轨道交通开展物流配送提供了理论指导。

提高货运班列质量 创建我国铁路货物快运新模式

介绍我国五定班列开行的现状及存在的问题,阐述发展货物快运体系所面临的新形势和必要性,并概括了创建我国铁路货物快运新模式的举措。

面向区间禁会要求的客货车共线运行图调整优化方法

针对客货车共线运行时存在的安全隐患,结合国铁集团对动车分散动车组列车与货物列车在区间内不交会的规定,对既有线列车运行图调整优化的问题进行了研究.通过0-1变量来判断相向而行的列车是否为不同类型列车,进而构建客车、货车在区间内禁止交会的约束条件,并以列车总旅行时间、与原列车运行图总偏差之和最小化为优化目标,建立0-1混合整数规划模型,采用Cplex求解器对模型进行求解.最后,以胶济铁路为例进行实例验证.算例结果表明:所提出的优化模型能够在确保客货车不在区间内交会的前提下,减少列车总旅行时间,提高线路整体运行效率.研究成果可为面向区间禁会要求的既有线运行图调整优化提供合理参考.

基于综合物流的铁路货运能力优化研究

铁路货运能力优化研究对于铁路运输能力提升具有积极的意义。在对经典列车开行能力优化分析的基础上,综合考虑整体物流系统,以网络内列车运行总成本与货物在货运站的库存惩罚的差值最大为目标,考虑发车数量、流量守恒等约束,建立基于综合物流系统的铁路货运能力优化单目标线形规划模型,并根据模型特征,设计基于整数编码的遗传算法进行求解。