On the Polygonal Wear Evolution of Heavy-Haul Locomotive Wheels due to Wheel/Rail Flexibility and Its Mitigation Measures

Wheel polygonal wear can immensely worsen wheel/rail interactions and vibration performances of the train and track,and ultimately,lead to the shortening of service life of railway components.At present,wheel/rail medium-or high-frequency frictional interactions are perceived as an essential reason of the high-order polygonal wear of railway wheels,which are potentially resulted by the flexible deformations of the train/track system or other external excitations.In this work,the effect of wheel/rail flexibility on polygonal wear evolution of heavy-haul locomotive wheels is explored with aid of the long-term wheel polygonal wear evolution simulations,in which different flexible modeling of the heavy-haul wheel/rail coupled system is implemented.Further,the mitigation measures for the polygonal wear of heavy-haul locomotive wheels are discussed.The results point out that the evolution of polygonal wear of heavy-haul locomotive wheels can be veritably simulated with consideration of the flexible effect of both wheelset and rails.Execution of mixed-line operation of heavy-haul trains and application of multicut wheel re-profiling can effectively reduce the development of wheel polygonal wear.This research can provide a deep-going understanding of polygonal wear evolution mechanism of heavy-haul locomotive wheels and its mitigation measures.

Experimental study and numerical simulation of the impact of under-sleeper pads on the dynamic and static mechanical behavior of heavy-haul railway ballast track

Laying the under-sleeper pad(USP)is one of the effective measures commonly used to delay ballast degradation and reduce maintenance workload.To explore the impact of application of the USP on the dynamic and static mechanical behavior of the ballast track in the heavy-haul railway system,numerical simulation models of the ballast bed with USP and without USP are presented in this paper by using the discrete element method(DEM)-multi-flexible body dynamic(MFBD)coupling analysis method.The ballast bed support stiffness test and dynamic displacement tests were carried out on the actual operation of a heavy-haul railway line to verify the validity of the models.The results show that using the USP results in a 43.01%reduction in the ballast bed support stiffness and achieves a more uniform distribution of track loads on the sleepers.It effectively reduces the load borne by the sleeper directly under the wheel load,with a 7.89%reduction in the pressure on the sleeper.Furthermore,the laying of the USP changes the lateral resistance sharing ratio of the ballast bed,significantly reducing the stress level of the ballast bed under train loads,with an average stress reduction of 42.19 kPa.It also reduces the plastic displacement of ballast particles and lowers the peak value of rotational angular velocity by about 50%to 70%,which is conducive to slowing down ballast bed settlement deformation and reducing maintenance costs.In summary,laying the USP has a potential value in enhancing the stability and extending the lifespan of the ballast bed in heavy-haul railway systems.

Dynamic effect of heavy-haul train on seismic response of railway cable-stayed bridge

This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.

Lateral Stability Analysis of Heavy-Haul Vehicle on Curved Track Based on Wheel/Rail Coupled Dynamics

Being viewed from the standpoint of whole system, the hunting stability of a heavy-haul railway vehicle on a curved track is investigated in this paper. First, a model to simulate dynamic performance of the heavy-haul vehicle on the elastic track is developed. Secondly, the reason of the hunting motion is analyzed, and a bifurcation diagram for the vehicle on the curved track is put forward to simulate the nonlinear critical speed. Results show that the hunting motion of the heavy-haul vehicle will appear due to the larger conicity, the initial lateral shift and the wheelset angle of attack. With the hunting motion appearing, the lateral shift and force of the wheelset are changed sharply and periodically with a wave of circa 3.6 m. There is obvious difference in the bifurcation diagram between on a curved track and on a tangent track. Relative to the centerline of the track, each vehicle body on the curved track has two stable cycles. As for the curved track with a radius of 600 m and a superelevation of 55 mm, the nonlinear critical speed of the heavy-haul vehicle is 76.4 km/h.

Dynamic performance of heavy-haul combined train applying emergency braking on straight line

A heavy-haul train-track coupled model is developed. Taking the emergency braking of the 2×104 t combined train as example, the train longitudinal impulse, the coupler dynamic behaviors and wheel-rail interactions of vehicles distributing in the different positions are analyzed. The results indicate that under the coupler compressing forces, the couplers of middle locomotives may tilt to the free swing limits, which induces the unidirectional tilt of their connected wagon couplers. Consequently, the coupler longitudinal forces produce the lateral components, and then affect the wheel-rail dynamic interaction. The performance of the middle locomotive and their neighboring freight wagons deteriorate significantly, becoming the most dangerous parts in the combined train. The wagons disconnecting with the locomotives can basically keep their couplers to stabilize in the centering positions, even though the maximum coupler longitudinal force acts on it. And its corresponding running safety also has little changes.

System integration and innovation of operating 20 kt combined heavy-haul train on Datong-Qinhuangdao line

Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December, 1992, totaling 653 km with the designed annual traffic volume of 1×108 t. In order to meet the demands of national economic development, the transport capacity of the line must be enhanced greatly. Depending on independent innovation, MOR, for the first time in the world,realizes the integration between GSM-R and Locotrol, the integration between 800 MHz digital radio and Locotrol, and the integration between a single set of Locotrol and SS4 locomotive. Meanwhile, CR develops equipment portfolio for heavy-haul through combining 2 high power locomotives of HXD series (means harmony) with controllable EOT. Relying on integration and innovation, it succeeds in operating 20 kt-level combined heavy-haul train on Datong-Qinhuangdao line, which tripled the annual traffic volume of the line from 1×108 t in 2002 to 3×108 t in 2007.

Finite element analysis on deformation of high embankment in heavy-haul railway subjected to freeze-thaw cycles

Finite element simulations are increasingly providing a versatile environment for this topic. In this study, a two-dimensional finite element analysis is conducted to predict the deformation of high embankment in Bazhun heavy-haul railway, China. A recently developed nonlinear softening-type constitutive model is utilized to model the be- havior of subgrade filling materials subjected to freeze-thaw cycles. For the convenience of practical application, the dynamic loading induced by a vehicle is treated as a quasi-static axle load. The deformation of this embankment with different moisture content under freeze-thaw cycles is compared. The results show that when subjected to the first freeze-thaw cycle, the embankment experienced significant deformation variations. Maximum deformation was usually achieved after the embankment with optimum moisture content experienced six freeze-thaw cycles, however, the em- bankment with moisre content of 8.0% and 9.5% deforms continuously even after experiencing almost ten freeze-thaw cycles. Overall, this study provides a simple nonlinear finite element approach for calculating the deformation of the embankment in changing climate conditions.

Simulation study on the influence of longitudinal dynamic force on extreme-long heavy-haul trains

Purpose–The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains,providing new insights and methods for their design and operation,thereby enhancing safety,operational efficiency and track system design.Design/methodology/approach–A longitudinal dynamics simulation model of the super long heavy haul train was established and verified by the braking test data of 30,000 t heavy-haul combination train on the long and steep down grade of Daqing Line.The simulation model was used to analyze the influence of factors on the longitudinal force of super long heavy haul train.Findings–Under normal conditions,the formation length of extreme-long heavy-haul combined train has a small effect on the maximum longitudinal coupler force under full service braking and emergency braking on the straight line.The slope difference of the long and steep down grade has a great impact on the maximum longitudinal coupler force of the extreme-long heavy-haul trains.Under the condition that the longitudinal force does not exceed the safety limit of 2,250 kN under full service braking at the speed of 60 km/h the maximum allowable slope difference of long and steep down grade for 40,000 t super long heavy-haul combined trains is 13‰,and that of 100,000 t is only 5‰.Originality/value–The results will provide important theoretical basis and practical guidance for further improving the transportation efficiency and safety of extreme-long heavy-haul trains.

Test and application of 60 kg·m^(−1) bainite rails for heavy-haul railway

Purpose-In order to develop high-strength,high-toughness and high-wear-resistance rails suitable for the development and application of heavy-haul railways.Design/methodology/approach-Based on the trial production of 60 kg·m^(−1) bainite rails,the Zeiss inverted optical microscope,transmission electron microscope and static hydraulic universal tester were used to test the microstructure and property of rail base metal and welded joints.Meanwhile,a trial laying of rails,wing rails of frogs and switch rails for turnouts was performed to systematically analyze their strength,toughness and wear resistance.Findings-The results show that the base metal of 60 kg·m^(−1) bainite rail is of a uniform microstructure,with a carbide-free bainite matrix,a few of stable residual austenite and M/A islands,and it features high hardness,good wear resistance and good strength-toughness balance.The welded joint is of a uniform microstructure and has good properties.Originality/value-A bainite rail,laid in a curve section of heavy-haul railway is able to serve for 48 months with a gross traffic tonnage of nearly 600 million tons,whose service life is more than one time longer than that of pearlite rail;the service life of the wing rail of frog and the switch rail for turnout with 60 kg·m^(−1) bainite rails is 3-4 times longer than that with U75V rails,and no serious damage occurs.The bainite rails also have strong peeling and spalling resistance.

Monitoring energy usage of heavy-haul iron ore trains with on-board energy meter for improving energy efficiency

Purpose-For billing purposes,heavy-haul locomotives in Sweden are equipped with on-board energy meters,which can record several parameters,e.g.,used energy,regenerated energy,speed and position.Since there is a strong demand for improving energy efficiency in Sweden,data from the energy meters can be used to obtain a better understanding of the detailed energy usage of heavy-haul trains and identify potential for future improvements.Design/methodology/approach-To monitor energy efficiency,the present study,therefore,develops key performance indicators(KPIs),which can be calculated with energy meter data to reflect the energy efficiency of heavy-haul trains in operation.Energy meter data of IORE class locomotives,hauling highly uniform 30-tonne axle load trains with 68 wagons,together with additional data sources,are analysed to identify significant parameters for describing driver influence on energy usage.Findings-Results show that driver behaviour varies significantly and has the single largest influence on energy usage.Furthermore,parametric studies are performed with help of simulation to identify the influence of different operational and rolling stock conditions,e.g.,axle loads and number of wagons,on energy usage.Originality/value-Based on the parametric studies,some operational parameters which have significant impact on energy efficiency are found and then the KPIs are derived.In the end,some possible measures for improving energy performance in heavy-haul operations are given.

Study on a segmented electro-pneumatic braking system for heavy-haul trains

The large longitudinal impact of heavy-haul trains is the main factor limiting their development,and the asynchronous nature of train-braking systems is the main cause of this longitudinal impact.In this paper,a segmented electro-pneumatic braking solution fully compatible with the existing freight-train braking system in China is proposed to improve the synchrony of train-braking systems.A simulation model for this braking system is developed based on air-flow theory,the 120 distribution valve and electronic control devices.The braking characteristics obtained from simulations are compared to those from the train-brake testing platform,and show high fidelity.On this basis,the effects of the new braking system on the braking capacity and longitudinal impact of a 20000 t heavy-haul train are analysed by further simulation.The results show that during service brakes,the segmented electro-pneumatic braking system can increase the braking capacity by 4.2–24.7%and reduce the coupler force by 21.6–68.0%.Therefore,it can be seen that the segmented electro-pneumatic braking system is a new type of electro-pneumatic brake that meets the needs of the Chinese railway network.It solves the problem of the longitudinal impact of heavy-haul trains satisfactorily,and its compatibility with the existing braking system(resulting in a reduced modification workload)makes it possible to maintain normal operations on heavy-haul lines while trains undergo modification.

Research on emergency rescue technology and equipment for train operation accidents on a heavy-haul railway network

Bridges,tunnels,cuttings and high subgrade account for a relatively large proportion in China’s heavy-haul railway system,where 10000 t of unit trains and 20000 t of combined trains are in operation.When a train operation accident occurs,it can easily cause vehicle intrusions,slant-span lines,tipping and stacking.Based on the viewpoint of system engineering,rescue methods such as hoisting,lifting,pulling and overturning are integrated,according to the characteristics of heavy-haul transport and the construction practice of train accident rescue system.A scheme of technical research and equipment configuration relating to heavy-haul railway rescue in China is put forward based on the situation—embankment,bridge,tunnel(including cuttings),ramp and curve rescue,and so on—and three-dimensional finite-element modelling and calculation checks on the key components are carried out.

Analysis of the different locomotive wireless multi-traction synchronous control systems for heavy-haul combined trains and their performance

This paper looks at the heavy-haul combined train composed of different types of locomotives and its distributed power control system with a combination of 800 MHz and TD-LTE wireless communication.It analyses some key characteristic parameters that affect the synchronism and communication of the differential wireless multi-traction synchronous control systems for heavy-haul combined trains.At the same time,in order to reduce the latency of instruction and information transfer between different types of locomotives,improve the time-limit certainty of wireless transmission and optimize the control quality of multi-traction control systems for heavy-haul combined trains,a synchronism optimization strategy based on the Markov decision process on the basis of Petri networkconstruction is proposed.Relevant experiments and tests are carried out to verify the effectiveness of the synchronism optimization of the control system,which provides a guarantee for improving the differential wireless multi-traction synchronous control system for combined trains and optimizing train control.

Exploration of key traction-running equipment and its problems on heavy-haul trains and research on technology development

In recent years,heavy-haul train technology has seen a number of innovations worldwide,and train traction-running technology has also made great progress,resulting in a rich pool of experience and a range of promising applications.This paper summarizes the key technologies of traction running in heavy-haul combined trains,especially locomotive and rolling-stock technology,traction technology,braking technology,control technology,communication technology and safety technology.At the same time,based on an analysis of practical applications,this paper further explores the main problems and urgent needs of traction equipment on heavy-haul trains.With an eye to the future,the heavy-haul railway system will develop in the direction of informatization,automation and intelligence,in order to build a greener,more energy-saving,safer and more efficient railway.This paper therefore looks forward to the technical developments of heavy-haul combined trains,and provides a reference for the development of heavy-haul railways.

Fatigue damage analysis of ballastless slab track in heavy-haul railway tunnels

A ballastless slab track,which is commonly used in the track structures of heavy-haul railway tunnels,was analysed based on field measurement data of the Fuyingzi Tunnel on the Zhangtang Railway.In accordance with the measured data,the dynamic load thresholds and distributions on the surface and bottom of the ballastless slab track were investigated.A fatigue damage analysis of the ballastless slab track was performed based on the dynamic load time–history curve.The results show that the ballastless slab track can accomplish train load attenuation and reduce the dynamic load from heavy-haul trains by 47.22%from the surface to the bottom.In addition,the distribution at the bottom of the ballastless slab track exhibited a triangular shape,and the dynamic load threshold at the line centre accounted for 78.67%of that at the track position.Meanwhile,the distribution at the surface was saddle-shaped;the dynamic load threshold at the track position accounted for 79.55%of that at the line centre position.The fatigue damage of the ballastless slab track was analysed effectively by combining the measured data and the linear fatigue damage theory.Moreover,the accuracy of the calculation results was verified based on the measured dynamic stress of the ballastless slab track structure.The dynamic action of the train load led to more-concentrated damage to the track bed,and the damage occurred earlier than that in the ordinary line.The axle load was the primary influencing factor of the track bed fatigue damage,and the damage mainly occurred in the track position.These results provide a theoretical basis for performing stress analysis and designing parameters for ballastless slab tracks in heavy-haul railway tunnels.

Design and implementation of a coal-dust removal device for heavy-haul railway tunnels

The Daqin Railway is China’s first electrified double-track heavy-haul railway line dedicated to coal transportation.Over the years of operation,the tunnels have been covered with a thick layer of coal dust,which also pervades in the air.Worse is that the coal dust has even buried the rail joints in some sections,making the repair and maintenance of the line difficult.This paper introduces a coal-dust removal device for railway tunnels that integrates pipeline transportation with dust-collection techniques.The device is mainly composed of a power system,a conveying system,a dust-filtration and collection system,and a control and protection system.The key technical elements of the system,such as the dust-extraction method and dust-filtration and collection parameters,are optimized based on the characteristics of the coal dust in the tunnel(obtained via field trials),which greatly enhances the adaptability of the device.Coal-dust removal efficiency reached over 20 t/h,which improves the working environment,reduces the intensity of manual work required and solves the problem of coal-dust removal from the most polluted area—within 500 m of the tunnel entrance.

Guidance and evaluation system for smooth operation of heavy-haul trains

The operation rules and methods for heavy-haul trains were studied and summarized according to the characteristics of the Daqin Railway,such as a large traffic volume,a high density and high-speed and difficult-to-operate heavy-haul trains.Combined with traction calculation and operation experience,these can be quantificationally decomposed into an evaluation standard for the smooth modularized operation of heavy-haul trains that can be recognized by computers.A train operation guidance system was designed to collect locomotive drivers’operation data,display the actual operation and standard curves in real time and give voice prompts and violation-operation alarms for safety-critical operation.In addition,software for operation analysis and evaluation was developed according to the quantified smooth operation standard.The smooth operation of heavy-haul trains was evaluated and statistically analysed through a comparative analysis of the actual operation records.Moreover,a train impact force detection device capable of monitoring the three-dimensional impact force of heavy-haul trains in real time was developed.Meanwhile,the evaluation standard for smooth operation was verified and optimized by real-time monitoring of the impact force of heavy-haul trains.Finally,on the basis of the above studies,a complete closed-loop management scheme for the smooth operation of heavy-haul trains was constructed,and the objectives of optimizing train operation strategy,standardizing drivers’operations and ensuring the smooth operation of trains were realized through application.

Refined model analysis of basement rock degradation mechanism of heavy-haul railway tunnel

This study investigated the degradation mechanism of the surrounding rock of a heavy-haul railway under a water-rich condition,based on the construction of the Taihangshan tunnel for the Wari Railway,a heavy-haul railway that used standard construction practices for axle loads of 30 t.Remote monitoring demonstrated that the coupling effect between the dynamic load of a heavy-haul train and the groundwater leads to the deterioration and hollowing of the surrounding rock.This study clarified the void evolution process and deterioration mechanism of the basement rock under the comprehensive influence of the groundwater–train dynamic load using a refined discrete element numerical simulation.The results revealed that the groundwater was the primary influencing factor in the deterioration of the lower part of the heavy-haul railway tunnel.Rock particles were gradually lost under the effects of long-term erosion due to groundwater and heavy-haul trains,which inevitably damaged the basement rock after the construction was completed.Based on this observation,the critical conditions for the deterioration and attenuation law of the physical parameters of the basement rock were obtained.The results of this study can provide ideas and serve as a reference for the forecasting and disaster treatment of basement rock damage in heavy-haul railway tunnels.

Linear active disturbance rejection control of heavy-haul train operation based on an interval type-2 fuzzy logic system model

The heavy-haul train(HHT)has large capacity and high efficiency,which represents the level of freight and makes the amelioration of control performance a trend in various countries.Improving the model reliability and increasing the anti-disturbance ability of the operation controller are two main ways to improve the operation control accuracy of HHTs.Herein,to describe the large nonlinear system more precisely,an interval type-2 fuzzy logic system(IT2FLS)is introduced to obtain a dynamic model.Then,a linear active disturbance rejection controller(LADRC)is designed to achieve precise operational control.In addition,the‘bandwidth method’is combinedwith the sparrowsearch algorithm(SSA)to solve the difficulty of controller parameters adjustment.Afterwards,the stability analysis of the closed-loop control system is given.The simulation experiments are conducted based on data collected from HXD1 locomotives driven by excellent drivers.Results show that the speed tracking error is no more than 0.5 km/h,and demonstrate that the proposed method significantly improves the operational performance of HHTs.

Research on the performance of heavy-haul rail breakage detection using track circuit

Rail breakage is one of the major safety risks in railway transportation.Because of the large axle weight,high density and large capacity of the heavy-haul railway,the damage to rail caused by heavy-haul train wheels will be more serious than that caused by ordinary passenger and cargo trains,resulting in a higher frequency of rail breakage.Taking the Daqin Railway Line as the research object,this paper analyses and discusses rail breakages occurring in interstation tracks and in-station tracks by establishing the ZPW-2000A track circuit calculation model considering the land leakage resistance between the rail line tracks;introduces the defining standards and measurement index of the broken rail coefficient to quantitatively analyse the influence of various influencing factors on the rail breakage inspection performance under the most unfavourable working conditions;and compares the model simulation data,the laboratory model data and the field test results to verify its effectiveness,so as to provide a reference and theoretical basis for the subsequent improvement and solution of the heavy-haul railway rail breakage problem.