1. Overview

2. Properties of CFRP

3. Current Status of CFRP Application in Rail Transit Equipment

4. Principle of electromagnetic shielding

5. Simulation Research

6. Conclusion

7. References

The carbon fiber composite materials have been widely used in the field of rail transit.Carbon fiber body is more advantageous than traditional material especially in weight.This paper introduces main characteristics of carbon fiber composites and outlines the principles of electromagnetic shielding effectiveness.Electromagnetic shielding characteristics of carbon fiber reinforced polymer (CFRP) was studied through electromagnetic shielding simulation technology and test compared with aluminum, aluminum alloy and carbon steel. Some suggestions are provided in terms of the CFRP electromagnetic characteristics. This research sets a foundation for the EMC design for railway vehicles.

Overview

Modern railway vehicles have undertaken improvement and optimization in the aspects of rail transit, intelligence, safety and comfort, especially the high-speed EMU trains. However, speed increase will not only rely on the design of powerful traction system but also on the lightweight design which plays a vital role in this aspect.For the weight, stainless steel is better than weatherproof steel. Aluminum alloy is better than stainless steel. However, carbon fiber reinforced composite has better advantages over aluminum alloy. The application of composites in the high-speed railway vehicles has been gradually enlarged from carbody interior, components and materials of equipment inside vehicles to the carbody structure. Carbon fiber composite will bring rail transit industry into a new stage[1]-[2]. Although CFRP presents excellent properties in various aspects, there are still more aspects of carbody materials to be satisfied for high-speed trains, such as fire performance, thermal insulation properties, corrosion resistance characteristic and electromagnetic properties. Upon comparison with previous car bodies made from steel and aluminum alloy, however less attention is paid to electromagnetic shielding properties of CFRP vehicles.

This paper improved the algorithm of swarm intelligence, and the adaptability of improved algorithm in the design of door-to-door full-loaded transportation of railway goods was analyzed. The optimization model of the door-to-door full-loaded transportation routing design was extended to the resourceexpandable optimization model of the door-to-door full-loaded transportation routing design to explore the influence of the change of railway and highway transportation distance on the system optimization. The improved algorithm of swarm intelligence was applied to solve the selected benchmark cases, and the comparison and analysis were conducted from both quantitative and qualitative aspects to verify their performance in solving continuous optimization problems. Two improved methods of intelligent algorithm were applied to the calculation example based on the coding system of the problem of the door-to-door transportation routing design of the resource-expandable railway freight, and the performance of their application to the optimization model of the route design system was verified. Then, input the compromise solutions into Simio for simulation analysis. The results of this paper can provide decision support for the routing design and decision reference for the location of the new station, and support the layout optimization of the stations for the railway transportation enterprises.

Introduction

With the implementation of the reform of railway freight organization and the unswerving promotion of the reform of railway corporation system, railway transportation enterprises expand cargo business from station-to-station transportation to door-to-door transportation, therefore, the design has become more complex. Facing the practical application of new complex environment, the swarm intelligence algorithm method has been widely applied in various practical fields, and the optimization results are presented in a reasonable amount of time. The results of this paper can provide decision support for the route design of railway transportation enterprises, so as to reduce the transportation cost and transportation time of the system. In order to explore how the changes of railway and highway transportation distance affect the transportation cost and transportation time, this paper takes into account the extensibility of transport resources, assumes that the departure stations and terminal stations are unknown or to be determined, and constructs the resource-expandable optimization model of the full-loaded door-to-door transportation of railway. Railway transportation enterprises need to arrange the departure stations and terminal stations for the multiple shippers, and also need to determine the location of the departure stations and terminal stations. Swarm intelligence (SI), commonly known as bionic computing, was first created by Beni and Wang in 1989 under the background of the development of cellular robot system. Due to its flexibility and versatility, as well as its high efficiency in solving nonlinear design problems, it has won great popularity among people.

Rail fastening systems on a slab track at railway bridge ends are often damaged, which increases the maintenance costs. The serviceability evaluation of a rail fastening system on a slab track at railway bridge ends is based on the assumption that the stiffness of the rail fastening system is linear. The behavior of the rail fastening system on slab track at the railway bridge ends is studied in detail in this study. In the experimental model, the abutment and pier of the railway bridge were considered to be directly connected to two H-beams through a rail and rail fastening systems. A stiffness model of the rail fastening system for the finite-element analysis was established by performing a clamping-force test. In the finite-element analysis, the rail fastening system was considered as both linear and nonlinear stiffness models. The experimental and numerical results were very similar when the rail fastening system was considered as the nonlinear stiffness model. With the same uplift force acting on the rail fastening system, the displacement results of the nonlinear stiffness model were larger than those of the linear stiffness model. Therefore, it is necessary to employ the nonlinear behavior of the rail fastening system and investigate a displacement-based design method of the rail fastening system when evaluating the serviceability of the rail fastening system on the slab track at railway bridge ends.

Introduction

With the exponential growth of high-speed railway (HSR) networks [1–3], construction of railway bridges is constantly increasing. Because bridges are essential parts of HSR infrastructures for crossing valleys, existing train lines, and other obstacles. In addition, the application of slab track systems [4,5] to the railway bridges is constantly increasing. The slab track systems have been developed and implemented in a number of situations, including high-traffic and high-speed lines, in a number of countries. The slab track is being installed to offer increased passenger comfort and require minimal maintenance over time. In the case of railway bridges with slab tracks, vertical deformation of girders can lead to excessive rail deformation at the bridge ends, which may result in a larger load being applied to the rail fastening systems, which is in contrast to ballasted track systems. The geometric tolerances and tension and compression forces have a significant influence on the design of closed and open bridge joints for slab track [6]. Additionally, in the case of a rail fastening system with high stiffness, a large load is generated in the slab track [7]. These problems at the railway bridge ends need to be more attention as the high-speed lines increase.

1. Overview

2. Common Address Interference Principle

3. Analysis of Vehicle-Mounted Antenna

4. Evaluation Methods

5. Engineering Application Cases

6. Conclusion

7. Reference

In order to verify that multiple vehicle-mounted antennas do not appear electromagnetic interference due to integration on the same railway vehicle,an evaluation method suitable for electromagnetic compatibility of vehicle-mounted antennas is proposed. Based on the analysis of the forming factors of antenna interference and the changes of electromagnetic environment before and after loading,the combination of antennas that may produce electromagnetic interference is chosen.Then,the isolation between selected antennas is measured to supplement the evaluation data.Finally,the electromagnetic compatibility between antennas is evaluated by calculating the energy matching of transceiver antennas.The method has been applied to the development of railway vehicles.

Overview

For the railway vehicle, multiple antennas are arranged on the platform with relatively limited space, which is more likely to cause common address interference between antennas.With the emergence of electromagnetic interference problems, vehicle electromagnetic compatibility(EMC) is highly concerned by operators, signal system suppliers, communication system suppliers and vehicle suppliers and other stakeholders. Evaluation of vehicle electromagnetic compatibility has become an important aspect of the development and application of rail transit vehicles.At present, the conformity of vehicle electromagnetic compatibility is mainly evaluated based on the electromagnetic compatibility test results, and the test is mainly conducted according to EN 50121 “electromagnetic compatibility of rail transit” [4].This standard covers the cable port and chassis port, but does not cover the antenna port. Therefore, the test group designed according to this standard cannot directly evaluate the electromagnetic compatibility between antennas after each wireless device is loaded.

During their lifetimes, tramway networks become increasingly susceptible to mechanical damage in the form of rail fractures. Understanding the underlying reasons, and initiating appropriate countermeasures may be facilitated by (computational) modeling tools. The development of such tools calls for a sound theoretical foundation. The latter is still largely missing, as the cross-sectional shapes of grooved rails employed in tramway networks differ significantly from those of (in this regard) well-investigated railroad systems. As a first step towards closing this knowledge gap, we here report on a novel beam theory approach allowing to compute typical shear stress distributions throughout the cross sections of grooved rails. Based on classical concepts, such as Bernoulli and Saint-Venant beam kinematics, cross-sectional boundary value problems for the related shear stress distributions are derived, and corresponding solutions are obtained in the form of 2D Finite Element approximations. This way, it is revealed that practically relevant loading scenarios induce distinctive shear stress concentrations. Remarkably, the positions of the latter agree well with fracture patterns observed in situ.

Introduction

In many urban areas, the tramway network is the backbone of the local public transport system [1–4]. Hence, the reliability of tramway networks is key for the functionality of public life in such areas. The primary causes for disturbances are fractured rails [5,6], as well as degradation due to wear and environmental influences [7,8]. It is evident that rail fractures occur if the loads acting onto the rails induce stress states which exceed the strengths of the steels the rails are made of. A purely experimental approach to the challenge of predicting where and when fractures occur turns out as difficult (if not impossible), given the huge dimensions of the problem (in terms of both size and load magnitude). This calls for computational approaches, and the current state of the art in the field may be briefly sketched as follows: The contact forces between wheel and rail have been quantified for different types of rails (i.e. railroad, subway, and tramway) [5,9–11]. Other modeling approaches are concerned with the estimation of residual stresses. This is often done based on the Finite Element (FE) method, with the main focus lying on Vignole rails [12–18], and an only marginal amount of work spent on tramway rails [19]. Residual stresses have been shown to arise in the rails from the straightening and bending processes prior to mounting the rails [10,12–18,20,21], and change, over time, due to the overrunning by wheels [9–11,22–24], hence under standard operation conditions [22–25]. Numerical methods have also been developed for crack propagation analysis in Vignole rails, either under consideration of residual stresses [27,26], or neglecting the latter [24,28].

1- Introduction

2- Literature review

3- Methods and data

4- Results and discussion

5- Conclusions and implications

References

Abstract

With the rapid development of rail transit, a vast amount of electric power is consumed each year. However, the generation of electricity, and especially coal power generation, is an important source of greenhouse gases. Therefore, it is very important to analyze the potential of carbon emission reduction of urban rail transit based on specific electricity consumption structures. In this study, 18 cities in China were taken as the research object, and backward analysis was used to analyze the proportion limit of coal power consumption for rail transit in each city under three scenarios from 2015 to 2017. By comparing the limit value with the actual coal power consumed by urban rail transit, we analyzed the potential carbon emission reduction of rail transit relative to other traffic modes. The study results supported several conclusions. First, the traffic demand is in direct proportion to the carbon emission reduction potential in rail transit. Second, for cities with high coal power consumption, the development of ground bus transit is more conducive to achieving carbon reduction targets compared with rail transit. Finally, promoting the development of rail transit technology and lowering the energy consumption per capita unit travel distance are the fundamental ways to increase the emission reduction potential of rail transit. Therefore, as a modern transportation tool, rail transit is not an absolute emission reduction advantage for all cities. A city needs to analyze its own resource structure and travel demand together, set up suitable traffic modes to realize green growth and sustainable development.

Introduction

With the increasingly prominent traffic problems globally, the priority development strategy of public transport, especially rail transit, has been adopted by many countries. Rail transit has been vigorously promoted because of its characteristically large transport volume and low pollution potential. According to the China Urban Rail Transit Association, a total of 34 cities in mainland China had opened urban rail transit at the end of 2017, totaling 165 lines and total annual traffic volume of 18.5 billion passengers. The total length of operation lines reached 5033 km, 3884 km (77.2%) of which involved subways. Rail transit is an important part of an urban passenger transport system, and plays a great role in relieving urban traffic congestion. However, urban rail transit operations rely mainly on power resources; with the increase in operating rail length, energy consumption is increasing (Sun et al., 2018). According to the statistics of the China Urban Rail Transit Association, the energy consumption of rail transit in China reached 12.226 billion kWh in 2017. China predominantly generates electricity by burning coal; therefore, the large amount of electricity consumed by rail transit results in large amounts of greenhouse gases from the electricity generation process (Dong et al., 2018). Because of the development of urban rail transit and the huge increase of carbon emissions, the economic cost and the aggravation of environmental pollution have restricted green growth and sustainable development of cities in China and elsewhere (Song et al., 2018). Reducing the carbon emissions of rail transit systems has become a problem of widespread concern in recent years. Therefore, whether rail transit has more emission reduction advantages than other traffic modes is a question worthy of further examination. The carbon emissions arising from the consumption of electric energy in rail transit mainly come from coal power generation, and there are great differences in the power supply structure in various regions of China (Chen et al., 2018). The north of China is rich in mineral resources and relies heavily on coal power. By comparison, water resources in the south of China are abundant, and hydropower occupies an important position in the region’s power structure. The cleanliness (in terms of environmental emissions) of power in different regions is not the same (Pei et al., 2015). Therefore, the carbon emissions from the generation of electric power that is consumed by rail transit are also very different throughout China.

1. Maintenance of railway axle and grinding process

2. Experimental investigations of the effect of grinding on fatigue specimens

3. On the effect of grinding on an axle with a crack defect

4. Conclusions

References

For security requirements, no fatigue failure of axles is admitted in railway industry. Design process of axles must ensure that there is no crack initiation during its life. Maintenance inspections guarantee that no defect initiates critical propagation of fatigue cracks. In order to remove surface defects, wheel grinding is realized during maintenance task. The present paper addresses a lifetime comparative study of an axle with and without grinding operation. The goal is to investigate the influence of the grinding parameters on the lifetime of axle. In the first part of the paper, the context of maintenance of railway axle is briefly described and the grinding process is presented. The grinding process modifies the roughness, the microstructure of the surface and induces residual stresses: some experimental results are presented. In the second part, the case of a ground axle is considered without defect. A study of the effect of the grinding process on the lifetime of fatigue samples is presented. In the third part, the case of a ground axle is considered with defects. In this case, a study of the effect of the grinding process on the lifetime is presented for different types of defects. Fatigue tests results on specimens are presented. Numerical simulations results for lifetime evaluation are also presented.

Maintenance of railway axle and grinding process

The railway axles are subjected to high mechanical loads. The risk of the occurrence of fatigue cracks is perfectly controlled by the design. In spite of this, cracks could be initiated in different zones of the axles on defects like shocks, corrosion pitting or machining striation. On the axle journal, the origin of cracks could be an anomaly in the bearings. On the seats of wheels, gear wheels or brake discs, the problem comes from the fretting. In the body, every defect could cause the initiation of cracks: corrosion, shocks or machining striation. To avoid such a failure, two philosophies are opposed. The first is based on the high frequent and regular check of axles by NDT to try to detect cracks before the fracture. The second is to check the entire surface at regular inspection of the axles to detect all defects that can lead to cracks. If defects are found in maintenance visits, these defects have to be erased by machining or grinding. SNCF chooses this second solution for the maintenance of the wheelsets. First axles are shot-blasted to strip painting, to perform magnetic particle testing. If some indications are found, surface around defect is grinded. The maintenance specifications impose criteria for this operation, geometry of the grinded area and direction of grinding. The documents also force to use specific equipment.