Heavy Haul Transportation Research Articles

An optimal scheduling method for heavy haul trains with virtual coupling technology

ABSTRACT Heavy haul transportation enjoys the benefits of cost-efficiency by using long trains, but suffers from high cost in combination process and low efficiency in bottleneck areas. Virtual coupling technology (VCT) is helpful in resolving the dilemma. In this paper, we propose an optimal method for scheduling the route, timetable, and combination scheme of heavy haul trains with VCT in an integrated way. Specifically, six groups of constraints are first established, in which the sequence and train length problems incorporated by virtual coupling are properly handled. Then, a combined objective function comprised makespan and total flowtime indicators is proposed to optimize the throughput and turnover rate and further speeds up the optimization convergence. Finally, the optimization problem equipped with the proposed constraints and the combined objective function is transformed into an integer linear programming problem and solved by GUROBI. Simulation results demonstrate the effectiveness and advantages of the proposed method in leveraging VCT, and the benefits of virtual coupling over traditional physical coupling for heavy haul transportation.

Research on the health monitoring and maintenance strategy of highway structuresg

Under the current background of The Times, China's economic and social development presents a good situation, the construction of transportation infrastructure has been better developed, and the highway transportation industry has made outstanding achievements. At the present stage, the highway transportation industry has become an important pillar industry of China's national economy, and is an important guarantee to promote economic growth and facilitate people's travel. Highway transportation infrastructure is an important foundation for China's national economic and social development, especially in the process of "Belt and Road" construction, highway transportation infrastructure has played a vital role. Under the influence of the increasing number of expressways and heavy-haul transport vehicles, there are also some problems in the highway traffic infrastructure. Therefore, this paper studies and analyzes the health monitoring and maintenance strategy of highway structure, aiming to provide some reference for further improving the health monitoring and maintenance work of highway structure in China.

Evaluating efficiency of railway transportation based on cross‐efficiency evaluation method and relative entropy evaluation method in China

AbstractRailway transportation system is one of the most important components of the integrated transportation system. A functional and efficient railway transportation system can be conducive to sustainable development of society and economy, thus highlighting the importance of studies on railway transportation efficiency. Therefore, this research proposes the cross‐efficiency evaluation method based on the relative entropy evaluation method (CERE) to evaluate railway transportation efficiency in China. Firstly, the research constructs an evaluation indicators system for railway transportation efficiency from the perspective of input‐output. Secondly, the paper obtains cross‐efficiency matrix by using the cross‐efficiency evaluation method (CE). Then, the study takes the obtained the cross‐efficiency matrix as the decision matrix of multiple criteria decision‐making (MCDM) problem, and applies the relative entropy evaluation method to evaluate the efficiency of railway transportation. Finally, the empirical analysis of the efficiency evaluation results for 18 railway transportation companies shows that, in 2019, Taiyuan Railway Transportation Company has the highest efficiency score, owing probably to a greater coal railway transportation demand and an advanced railway heavy haul transportation technology; railway transportation companies in the Eastern China typically have the highest efficiency scores, owing probably to a greater regional railway transportation demand.

Engineering Application of Nanomaterial and Ferroelectric Domain Polarization to the Dynamic Structure of the Surrounding Rock of Heavy-Duty Railway with Small Clear Intersection Tunnel

With the development of national railways and railways as one of the important channels for heavy-haul transportation, the construction of heavy-haul railways must be a rapid development, which makes it inevitable that the heavy-duty situation of small-distance interchange tunnels will appear. Nanomaterials refer to materials that have at least one dimension in the three-dimensional space in the nanoscale range (1 nm∼100 nm) or are composed of them as basic units. Ferroelectric domain polarization refers to the existence of electric domains in ferroelectrics, electric domains refer to small regions with the same spontaneous polarization direction, and the boundaries between electric domains and electric domains are called domain walls. It is also urgent to study the dynamic structure of the surrounding rocks of heavy-duty railways. This article aims to study the use of nanomaterial and ferroelectric domain technology to improve the overall strength, wear resistance, toughness, and other properties of steel to ensure the safety of the surrounding rock dynamic structure of the heavy-duty railway in the small clearance intersecting tunnel. Moreover, on this basis, this article proposes the method of spraying steel with nanomaterials and the use of ferroelectric domain polarization technology. The strength and wear resistance of steel can be improved under different nanomaterial content and the degree of ferroelectric domain polarization. Sustainability and toughness have been improved, respectively. After the wear resistance experiment and analysis, the experimental results of this article show that the impact resistance of the steel increased by 18.75%. When 0.012% of CeO2 is added, the impact toughness of the steel is increased to the maximum of 3.4 J, an increase of 16.31%, and a 37% increase in wear resistance. Under the premise of ensuring the demand for heavy-duty transportation, the safety performance and sustainability of transportation are greatly improved.

Prediction Method of Heavy Load Wheel/Rail Wear Mechanical Properties Based on GA-BP Hybrid Algorithm

Due to its large axle load and high-density operation mode, heavy haul transportation has greatly improved the cargo transportation capacity, and is receiving unprecedented attention from all countries in the world. Since the development of heavy haul freight transport in China, wheel rail wear has been paid much attention, especially the use of heavy axle load locomotives on upgraded heavy haul lines, which makes reducing wheel rail wear and damage become a technical problem to be solved urgently. Considering that there are too many mechanical parameters involved in the prediction of heavy load wheel rail wear mechanical properties, the prediction accuracy is reduced. Therefore, this paper proposes a method based on GA-BP hybrid algorithm to predict the mechanical properties of heavy load wheel/rail wear. Hertz contact theory is used to simplify the wheel rail contact relationship, and the wheel rail contact model is established. According to the wheel/rail contact model, the expressions of heavy load wheel/rail in the case of vertical, horizontal, direction and gauge irregularity are analyzed, and based on this, a mechanical model of heavy load wheel/rail wear is established. In order to solve the problems of slow convergence speed and easy to fall into local optimum of BP neural network in the prediction of heavy load wheel/rail wear mechanical properties, the global convergence of genetic algorithm is used to optimize the BP network. According to the obtained mechanical parameters of heavy load wheel/rail wear, the mechanical parameters are input into the optimized model, and the relevant prediction results are output. So far, the research on the prediction method of heavy load wheel/rail wear mechanical properties based on GA-BP hybrid algorithm has been realized. The experiment is designed from three aspects of wear degree, hardness and tensile strength, and compared with the measured value, reference [4] method, reference [5] method and reference [6] method to verify the effectiveness of the proposed method. The experimental results show that the predicted results of wear degree, hardness and tensile strength by this method are closer to the measured results. It is proved that the proposed method has higher prediction accuracy and better practical application effect.

INVESTIGATION ON THE STABILITY AND DYNAMIC RESPONSE OF SOIL FOUNDATION UNDER HEAVY HAUL RAILWAY TRACKS

The roadbed is the most deformable and most heterogeneous segment of the railroad track foundation, which states the principal factor deciding the efficiency of the street, and the primary factor behind deterioration of path and its components, leading to the rise in the expense of current maintenance. Notwithstanding the expanding dynamic effect of trains on the railroad framework resulting from heavy haul transportation system, this issue turns out to be especially significant. In this paper, an examination is made of the issue of degradation and giving the strength to the track foundation with an increased axial load on the track, with a strict attention on examination of the excitation mechanisms of cyclic effects and the procedure of their damping by the soil environment. The principal kinds of deformations and defects are portrayed; the mechanisms and explanations behind their occurrence are studied in this paper. Much consideration is paid to the investigation of soil degradation procedures of the roadbed under the dynamic effect of heavy trains. Different components of the roadbed are taken into account, which require support for operation under substantial heavy traffic and huge axial loads. The advanced strategies and structures of strengthening the roadbed are portrayed, the utilization of which permits to build the proficiency of the heavy haul transportation. Taking everything into account, extensive research is carried out to address the issue of ensuring the stability of the roadbed in the association of heavy haul traffic.

A Scheduling Approach for the Combination Scheme and Train Timetable of a Heavy-Haul Railway

Heavy-haul railway transport is a critical mode of regional bulk cargo transport. It dramatically improves the freight transport capacity of railway lines by combining several unit trains into one combined train. In order to improve the efficiency of the heavy-haul transport system and reduce the transportation cost, a critical problem involves arranging the combination scheme in the combination station (CBS) and scheduling the train timetable along the trains’ journey. With this consideration, this paper establishes two integer programming models in stages involving the train service plan problem (TSPP) model and train timetabling problem (TTP) model. The TSPP model aims to obtain a train service plan according to the freight demands by minimizing the operation cost. Based on the train service plan, the TTP model is to simultaneously schedule the combination scheme and train timetable, considering the utilization optimal for the CBS. Then, an effective hybrid genetic algorithm (HGA) is designed to solve the model and obtain the combination scheme and train timetable. Finally, some experiments are implemented to illustrate the feasibility of the proposed approaches and demonstrate the effectiveness of the HGA.

A fast simulation approach to assess draft gear loads for heavy haul trains during braking

Train traction and brake dynamics simulations can be used to improve the safety and efficiency of heavy haul transportation. Virtual models can be used to analyze many operational conditions that are expensive or inviable to be measured due to costs and security risks. This paper presents a low computational cost simulation model that encompasses the longitudinal dynamics equations and the pneumatic brake system behavior. The model is used to evaluate the effects of the locomotive traction/dynamic-brake and of the pneumatic brake delays in the draft gear forces. A real-world scenario was analyzed, in which a standard train control procedure was applied for 168 ore freight cars propelled by two locomotives. For this analysis, the model was able to perform up to 8 simultaneous parallel simulations with a processing time of 607 s to conclude a route of 2884 s, which is very suitable for this kind of investigation.

Tempered Bainite and Martensite Embrittlement in Microalloyed Steel for Forged Railroad Wheel to Heavy Haul Application

Abstract This research shows two new microalloyed steels with niobium (Nb) for railroad wheels (Nb1 and Nb2) applied on heavy haul transportation (load over 30 tons/axle). The steels have mixed microstructure composed of pearlite and bainite (finished wheel rim section), and another one composed of martensite with bainite (black wheel section removed on machining) obtained by continuous cooling quenching heat treatment followed by tempering. The bainitic and martensitic microstructure are sensitive to the temper embrittlement phenomenon; therefore, knowing the embrittlement temperature range of these steels is mandatory in order to avoid such an event in the tempering process. Charpy specimens were extracted from the rim of railroad wheels, austenitized (860 oC), quenched in water for four minutes, and tempered at different temperatures to obtain the embrittlement curve. Three materials were compared: AAR (Association of American Railroads) Class C steel with pearlitic microstructure (not sensitive to embrittlement), Nb1, and Nb2 microalloyed steels with martensitic, bainitic, and pearlitic microstructures. The microalloyed steels have niobium (Nb), molybdenum (Mo), and silicon (Si) addition. The effect of Si content and the microstructure (analyzed by Scanning Electronic Microscope (SEM)), regarding the embrittlement phenomenon, was also studied. The microstructure of Nb2 steel was analyzed by with Transmission Electronic Microscope (TEM) for improving its characterization.

Wheelset-rail mechanical model for a steady-state dynamic condition and prediction of rolling contact fatigue locci

In railway heavy haul transportation, the wheel-rail contact interaction has a strong influence on the performance of the entire system. According to the vehicle longitudinal movement conditions - straight/curved tracks and travel speed, contact interaction takes place on different portions along the wheel/rail geometric profiles. Determining wheel/rail contact patches is fundamental both for vehicle dynamics and to predict the locci prone to rolling contact fatigue (RCF), due to high contact pressures. This work presents a quasi-static model to determine the wheel-rail contact locations and pressures for a given steady-state scenario of straight or curved track. The model is able to consider generic wheel and rail profile geometries with several contact pointwise interactions. Each contact pair is solved by the called ‘master-master methodology’, developed generally for a 3D environment. A proposed simplification leads to a two-dimensional model, able to produce results in fast processing time and very low computational cost. The result gives predictions related to RCF-prone location. The model is motivated for application together with a methodology to quantify the accumulated contact pressure, considering a family of distinct wheelsets and their combined interactions with the rails. We present a case study considering real measured wheel and rail profiles.

Modelling and control of a novel AT-fed co-phase traction power supply system for electrified railway

A large unbalanced current injected into the power gird and the neutral sections at the exits of traction substations have been the outstanding obstacles in conventional single-phase 25 kV AC traction power supply systems (TPSS). In order to meet the requirements of high-speed and heavy haul transportation systems, a novel autotransformer (AT)-fed co-phase TPSS is proposed, which can provide continuous power for the trains with high power quality (PQ). In this research, the electrical configuration of the new TPSS is presented, which is structured with Vx-connection traction transformer (TT) and power flow controller (PFC) adopting the modular multilevel converter (MMC) topology. Furthermore, the mathematic model of the novel system is built. The unbalanced current and the reactive power caused by traction load can be compensated effectively based on power balance principle. Moreover, a hierarchical control strategy is designed including upper optimized PQ compensation algorithm and low-layer PFC control, which can coordinate dynamic characteristics between different working patterns. Finally, the validity of the control method and the performance of the system are demonstrated by case studies. The results indicate that compared to the conventional co-phase TPSS, the proposed co-phase TPSS is able to reduce the compensation capacity by up to 59%.

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

Abstract Bridges, tunnels, cuttings and high subgrade account for a relatively large proportion in China's heavy-haul railway system, where 10 000 t of unit trains and 20 000 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.

Periodically intermittent cruise control of heavy haul train with uncertain parameters

With the objective to promote the efficiency of heavy haul transportation, this paper investigates the efficiently intermittent cruise control problem for heavy haul trains. Based on the concept of periodically intermittent control, the closed-loop form of the error dynamic state-space model for heavy haul trains is given considering uncertain parameters, which is different from existing heavy haul train control methods in that the control forces are only provided in part of the running period. To facilitate the controller design, a set of linear matrix inequalities (LMIs) are presented as the sufficient conditions for the existence of the periodically intermittent controller, which guarantees both the speed tracking error and the relative coupler displacements are exponentially stable at the equilibrium state. Simulation results indicate that the proposed control scheme can significantly improve the control efficiency without sacrificing too much on speed tracking performance.

Development of Niobium Microalloyed Steel for Railway Wheel with Pearlitic Bainitic Microstructure

Heavy haul transportation (load over 30 tons/axle), as well as the axle load, has been more and more used in Brazil and worldwide. The stress generated in the wheel-rail contact with loads up to 30 tons/axle is around 760 MPa, which causes premature wear and cracks of conventional wheels (AAR (Association of American Railroads) class C). Microalloyed wheels are fundamental on heavy haul transport, whose main function is to combine high hardness, ductility, and yield strength of the material in order to prevent shelling. The main purpose of this research is to develop a new microalloyed wheel steel with niobium addition that meets all the requirements of the AAR class D material with mixed microstructure composed of pearlite and bainite. The 0.71C/0.020Nb steel developed in this study (Nb material) for railroad achieved the standards required for AAR class D in all mechanical properties, with fracture toughness higher than the usual vanadium microalloyed steel used in comparison. The Continuous Cooling Transformation (CCT) diagram showed the presence of bainite even at very low cooling rate, in the range between 0.3 - 2 °C/s. These cooling rates to form bainite are much lower than those observed in other steels with similar composition.

Effect of manufacturing residual stress on the fatigue life of railway wheels for heavy-haul transportation

The present work aims to compare the effect of the residual stress from the thermal treatment process (TTP) on the estimate of fatigue life of railway wheels - class C, both with and without residual stresses field from thermal treatment process. A 3D finite element method model is used to calculate the thermal treatment process and the rolling contact between rail and wheel. With the stresses calculated in this region, the study estimates the life under fatigue until a crack arises. The crack, when propagated, can result in shelling, which is one of the types of failure with significant economic importance to railroad maintenance. The model primarily uses the elastoplastic approach, then adds residual stresses from the thermal treatment process of railway wheels. ABAQUS® software is used for the numerical processing, in parallel with specially developed techniques to reduce the computational cost without causing loss of accuracy of the results. The fatigue life of the railway wheel before crack initiation is determined by the modified Dang Van high-cycle fatigue criterion. Given the assumption that the wheel radius does not change during rolling, the elastic shakedown phenomenon occurs in a few loading cycles. The high-cycle life for the wheel is estimated using the variation in the stress field, both with and without residual stresses from the thermal treatment process. The results of the numerical simulation showed that the von Mises stresses in railway wheels with thermal residual stresses are lower than in wheels without thermal residual stresses. The elastic shakedown phenomenon happened in three load cycles in the wheel model with thermal residual stress and in four load cycles for in the wheel model without thermal residual stress. However, this small difference in cycles caused by the thermal treatment process has a significant effect on the fatigue life. The modified Dang Van’s fatigue criterion showed that railway wheels with thermal treatment have 43.2% more life than railway wheels without it.

Progression of plastic strain on heavy-haul railway rail under random pure rolling and its influence on crack initiation

The present work evaluates the plastic strain accumulation on railway rails for heavy-haul transportation and the effect of them on the life cycle and the stress-strain responses considering random loading passes of normal loads on the top of rail for wheel-rail pure rolling conditions. The normal pressure distribution on the contact region was estimated by the Hertz theory and applied on the surface of the rail in a tridimensional elastoplastic finite element model. Multiaxial Dang Van criterion was applied to estimate the life to crack nucleation. The results show that the level of plastic accumulation presents distinct magnitudes depending on the position analyzed, reaching similar plastic accumulation in analogous positions on the subsurface after several passes, for two different starting positions. That result is fundamental for life analyses, since indicates that, no matter the starting point, the computed life cycles always stabilizes after a few number of cycles. From that, the fatigue life to shelling can be estimated using high cycle models.

Study on service performance of 880 MPa-grade and 980 MPa-grade rail steels

With the rapid development of economy in China, the requirement for railway passenger and cargo transportation becomes higher and higher. Increasing speed and developing heavy-haul transportation can effectively improve the transportation capacity of railway. The requirement for rail steels with higher ability of abrasion resistance becomes urgent. Two kinds of rails, i.e., 880 MPa-grade and 980 MPa-grade rail steels, were laid on cargo line with 500 m short radius curve. The service performances of the tested steels were continuously tracked and analyzed during operation of total 22.5 million tons loads. Macro morphology, light band width, surface hardness and profile of rails were investigated. The results show that the performance of 980 MPa-grade rail steel is superior to that of 880 MPa-grade rail steel at same circumstance. Therefore, 980 MPa-grade rail should be selected in the cargo line with small radius curve.

A review of dynamics modelling of friction draft gear

Longer and heavier trains mean larger in-train forces and more complicated force patterns. Practical experience indicates that the development of fatigue failure of coupling systems in long heavy trains may differ from conventional understanding. The friction-type draft gears are the most widely used draft gears. The ever developing heavy haul transport environment requires further or new understanding of friction draft gear behaviour and its implications for train dynamics as well as fatigue damage of rolling stock. However, modelling of friction draft gears is a highly nonlinear question. Especially the poor predictability, repeatability and the discontinuity of friction make this task more challenging. This article reviews current techniques in dynamics modelling of friction draft gears to provide a starting point that can be used to improve existing or develop new models to achieve more accurate force amplitude and pattern predictions.

Optimization for Coal Heavy Haul Transportation Assembly Scheme Problem Using Genetic Algorithm

Thispaper presents aCoal Heavy Haul Transportation Assembly Scheme Problem (CHASP), in which the time consuming functions, assembly number constraints and assembly weight constraints etc are considered. The time consuming costs consist of residence time and disassembly time. The disassembly time functions are usually nonlinear functions of unit train departure directions. Then, a nonlinear 0-1 programming is formulated for the problem and solved by lingo mathematical solver. Considering the complexity of the problem, a kind ofGenetic Algorithm is proposed to solve it. Extensive computational experiments are taken on randomly generated data, the detailed results are given and the genetic algorithm is shown to be efficient.

Analysis of Incidence of Rail Failure and Track Composite Irregularity State Forecast

Rail failure and track composite irregularity is the source of violent harassment of the wheel-rail system. Track irregularity has significant impact on the driving security and stability of the train. At present, the focus of the Chinese railway development is high speed, heavy haul and shortcut transportation, thus the influences of rail failure and track composite irregularity will be more remarkable, which has become a primary factor that limits the running speed. This paper analyzes the characters of rail failure and formation mechanism of the track irregularity, forecasts the trend of track irregularity development and explores the hidden risks that might occur and influence the safety of railway traffic.