Train Braking Research Articles

Numerical simulation and optimization on opening angles of aerodynamic braking plates sets for a maglev train

The aerodynamic braking has become an attractive option with the continuous improvement of train speeds. The study aims to obtain the optimal opening angles of multiple sets of braking plates for the maglev train. Therefore, a multi-objective optimization method is adopted to decrease the series interference effect between multiple sets of plates. And the computational fluid dynamics method, based on the 3-D, RANS method and SST k-ω turbulence model, is employed to get the initial and iterative data. Firstly, the aerodynamic drag and lift are analysed, as well as the pressure and velocity distribution of the flow field with the braking plates open at 75°. Then, the aerodynamic forces of each braking plate pre and post optimization are compared. Finally, the correlation between each set of braking plates and the optimized objective is analysed. It is found from the results that the aerodynamic drag and lift of the train have significant differences with or without multiple sets of braking plates. Additionally, the design variable corresponding to the number of iterations of 89 is taken as the relative optimal solution, and its opening angles of braking plates (B2-B5) are 87.41°, 87.85°, 87.41°, and 89.88°, respectively. The results are expected to provide a reference for the opening angles design scheme for the future engineering application of high-speed maglev train braking technology.

Evaluation of the dynamic behaviors of a train braking system considering disc–block interface characteristics

Disc–block interface properties have prominent influence on the dynamic behaviors of train braking systems. In this study, the tribological characteristics of small-scale train friction blocks with different perforation diameters at the centre of the block surface were investigated using a disc–block test rig. And the Stribeck model parameters of the disc–block friction interface were identified to intuitively characterize the evolution law of stick–slip characteristics with the variation of block perforation diameters. Then, a trailer bogie braking system model of a high-speed train considering the coupling effects between the essential brake unit, wheelset and bogie frame was established. And the identified Stribeck parameters were introduced into the proposed braking system dynamics model to establish a relationship between the friction characteristics of the disc–block interface and the dynamic behaviors of the train braking system. Based on this, the cross-scale analysis was performed to evaluate the dynamic performance of a train braking system affected by the perforated friction block via classical stability theory and numerical simulation. The results show that the friction block with a perforation diameter of 3 mm can effectively suppress the stick–slip vibration of the disc–block friction interface, then reducing the oscillation of system components and enhancing the stability of the entire trailer bogie system.

Effect of tool tilt angle on microstructure, mechanical properties and fracture behavior of dissimilar friction stir lap welding joint of SiCp/ZL101 and ZL101

In order to achieve the lightweight goal of urban rail train braking system, friction stir lap welding (FSLW) was used to weld SiCp/ZL101 and ZL101 sheets to prepare a new type of brake disc material. The effects of different tool tilt angles (TTAs) on microstructure and mechanical properties of the welding joints were systematically studied. The TTA had a significant effect on the microstructure and defect formation of the dissimilar FSLW joints. There were tunnel defects under the advancing side at 1° and 2°. Internal defect-free weld structures were formed at 3° and 3.5°. A large number of dislocations caused by plastic deformation remained in the microstructure of the weld region at 1° and 2°, and the transformation of the microstructure of the weld region at 3° and 3.5° was dominated by dynamic recovery and dynamic recrystallization. The distribution of SiC particles in the nugget area was uniform, and the grains were obviously refined. With the increase of the TTA, the average grain size of the nugget area increased, the average size of the SiC particles decreased, and the average hardness of the nugget area increased. The four samples all formed a transition zone with good metallurgical bonding at the welding interface. The shear strength of the welding joints increased first and then decreased with the increase of the TTA. In the absence of welding defects, the shear strength reached the best level of 130.71 MPa at 3°. Both shear and tensile fractures were ductile fractures.

Energy-Efficient Optimization Method of Urban Rail Train Based on Following Consistency

Because of the short distance between stations in urban rail transit, frequent braking of urban rail trains during operation will generate a large amount of regenerative braking energy. Urban rail trains can reduce their actual traction energy consumption using regenerative braking energy. Therefore, an energy-efficient optimization method for urban rail trains is proposed. By taking the punctuality of trains as the premise, the weighted acceleration of trains is taken as the synergetic variable, the synergetic coefficient is introduced to construct the following consistency model, and its convergence is proved. By analyzing the influencing factors of the following consistency coordination time, an adaptive parameter adjustment strategy is designed to solve the latest secondary traction time and the corresponding maximum speed of the primary traction. In order to save communication resources, the event trigger function is used to construct trigger conditions, and the consistency algorithm is used to update the cooperative controller. The simulation results show that the weighted acceleration of the follower train achieves the following consistency on the premise of ensuring punctuality, and the actual traction energy consumption of the follower train is reduced by 5.73%. The proposed method provides a new strategy for the energy-efficient operation of urban rail trains.

Co-simulation methods for train braking dynamics

The development of train dynamics models usually started with simplified empirical air brake models. Fluid dynamic air brake models are sometimes required for train dynamics simulations to utilise their advantages in physical descriptions and model scalabilities. Due to the high complexity of fluid dynamic air brake models, the most economic approach to add such models to train dynamics simulation is via co-simulations. This paper presents three methods that can be used for co-simulations of train braking dynamics. These models are based on Transmission Control Protocol/Internet Protocol (TCP/IP), Open Multi-Processing (OpenMP), and Message Passing Interface (MPI) techniques, respectively. Requirements for co-simulations of train braking dynamics are discussed. Code structures regarding how to implement these techniques for train braking dynamics simulations are presented and discussed. Demonstrative simulations using dummy programs are presented to show the effectiveness of these methods. Comparatively, OpenMP, MPI, and TCP/IP have an increasing level of complexity for implementations as well as commination time overhead. OpenMP and MPI also allow parallel computing to increase computing speeds. For the case of train braking dynamics simulations, the authors’ recommendation regarding the optimum application sequence is OpenMP, MPI, and TCP/IP.

Friction-induced vibration and noise characteristics, and interface tribological behavior during high-speed train braking: The effect of the residual height of the brake pad friction block

A tribology test was carried out on a test device to simulate the braking performance of a high-speed train and investigate the effect of the friction block's residual height on friction-induced vibration and noise (FIVN) characteristics and interface tribology behavior. A finite element model (FEM) of the test device was established using the real boundary conditions and component material parameters. A wear simulation of the friction block was performed, and the Archard wear equation was used to obtain the surface wear of the friction block after stable friction had occurred. Complex eigenvalue analysis (CEA) and implicit dynamic analysis (IDA) were carried out. The effect of the friction block's height on the surface wear level, the complex mode and dynamic response, and the interface contact behavior are discussed. The results show that the friction block wears at an angle due to the friction force at the braking interface. Thus, the contact stress occurs predominantly at the leading edge of the friction block, leading to significant wear, high temperatures, and eccentric wear of the friction block. The taller the friction block, the larger the inclination angle is, and the more significant the eccentric wear degree is. Excessive wear at the leading edge causes debris to enter the brake interface. As a result, the wear surface of friction block is significantly damaged, including large contact plateaus and extensive exfoliation and ploughing. This damage increases the complexity of the braking interface's tribological behavior and causes high-intensity FIVN. However, the inclination angle decreases as the friction block's height decreases, resulting in better wear behavior of the friction interface and lower FIVN intensity. Although the friction block height significantly affects the intensity and evolution of FIVN, it does not change the system's inherent frequency.

Stick–Slip Characteristic Analysis of High-Speed Train Brake Systems: A Disc–Block Friction System with Different Friction Radii

Inspired by the difference in the friction radii of the pads from the high-speed train brake system, stick–slip experiments for a disc–block friction system with different friction radii were carried out via a test device. Based on the test results, the stick–slip vibration characteristics of the disc–block friction system with variation in the friction radius were analyzed, and the corresponding Stribeck model parameters in exponential and fractional forms were identified. The experimental results show that with an increase in the friction radius the vibration amplitude first increased and then decreased and the frequency of stick–slip vibration increased. The identified Stribeck model parameters show that the decay factors increased, the static friction coefficient decreased, and the dynamic friction coefficient decreased first and then increased as the friction radius increased. Moreover, the identified Stribeck model in an exponential form can more accurately reflect the stick–slip characteristics of a disc–block friction system than the model in a fractional form. It can be further applied in the investigation of the dynamic behaviors of high-speed train brake systems.

Establishing the impact of empty freight trains on the capacity railway lines

Currently, according to the standard schedule of Uzbekistan Railways JSC, the timing of departure, acceleration, and braking of freight trains is determined uniformly for different weight compositions on each section of the railway track. This, in turn, does not allow for an accurate assessment of the level of utilization of the existing permeability capacity of the railway section. In this study, the impact of accounting for the period of the schedule based on the proportion of freight trains of different weights in the movement schedule is examined with respect to the permeability capacity of railway sections. Uzbekistan Railways JSC has demonstrated that the existing permeability capacity of single-track and double-track railway sections can be increased by 7% and 5%, respectively, under existing operating conditions.

Research on the Influence of Urban Subway on Neutral Current of High-Voltage Substations Along the Line Under Complex Environment

During the operation of the urban subway, there will be stray current leaking into the ground, which may invade the neutral point of the transformer along the line, causing the working magnetization curve of the transformer core to shift, thereby causing the direct-current (DC) bias effect of the transformer. Since there are unknown parameters in the equivalent circuit model of the stray current of the subway, in order to simplify the process of the influence of the subway operation on the neutral current, based on the analysis of the formation mechanism of stray current, a real subway line has been selected and a monitoring platform in the nearby high-voltage (HV) substation has been built to record the neutral current. Meanwhile, through the on-site recording of the entry and exit time of subway trains at four consecutive stations, the running trajectories of the subway trains can be reversed. According to the trajectory of the subway train, the recorded neutral current was re-divided into time periods, and the synergistic analysis of the neutral current and the train trajectory in the corresponding time period was carried out. The neutral current measurement results for 4 consecutive days indicate that the influence of the subway train on the neutral current of the substation is mainly the influence of the unbalanced load, and the degree of the unbalance mainly comes from the distance and the acceleration and braking of the subway train. The trajectory of the subway train is related to the amplitude of the neutral current. The closer the subway train is to the substation, the greater the impact on the neutral current.

Research Results of the Operating Efficiency of the Electric Train Brake Air System

This document discusses the identified problems of the electric train braking system operation in the autumn-winter period. The results of observations are presented. The results of calculating the amount of condensate released during the 1 hour of compressor operation at a certain ambient air temperature are presented. Engineering calculations were performed. A technical solution is proposed to improve the efficiency of pneumatic equipment by installing heated purge valves on the main instead of conventional valves to prevent freezing.

Реверсивный инжиниринг в исследовании элементов тормозных систем

Braking efficiency plays an essential role in increasing the local and maximum train speeds. Braking of railway rolling stock directly depends on successful operation of both mechanical and pneumatic parts of the train braking system. The reliability and efficiency of rolling stock brakes necessitate the regular search for new scientific approaches to the study of topical issues in this technical field. The reduction of the braking distance, growth of the local traffic speed, increase in the working resource of consumables are the key evaluation metrics of the task being solved, the ultimate goal of which is to increase profits, reliability and safety in the transportation process. One of the new digital approaches to the study of fatigue wear of key elements of the train braking network is reverse engineering (3D scanning). In the course of the study conducted by the authors, the method of reverse engineering was tested, the object of which was the brake pad of the railway rolling stock. The testing method is described, which is based on a new approach to the study of elements of train braking systems. The result of the study was that the authors obtained a digital 3D model of a real brake pad with a certain degree of wear.

Diagnosis of brake friction faults in high-speed trains based on 1DCNN and GraphSAGE under data imbalance

A braking friction fault diagnosis method based on one-dimensional convolutional neural network (1DCNN) and GraphSAGE network is proposed to solve the problem of fault imbalance samples in actual high-speed train braking friction operation, taking into account the correlation between different fault features. To begin, the original sample is created using the friction interface state characterisation parameters such as vibration noise, vibration acceleration and friction coefficient. Second, the graph is built using the sample’s characteristics as well as the Jensen-Shannon divergence between each sample. The 1DCNN is then used to extract and compress the graph node features; Next, the GraphSAGE is used to aggregate the information of each node in the graph, compensating for the neural network’s inability to learn the features of small samples and ensuring that all kinds of fault information are fully extracted. Finally, GraphSAGE outputs the braking friction fault state category to realise braking friction fault diagnosis with imbalanced data. The proposed network was tested using various imbalanced data sets and it was discovered that even with fewer fault samples and more normal samples, the network can still achieve at least 93.83% effective diagnostic accuracy. The effectiveness of the proposed network for each braking fault identification is further verified using precision, recall, F1 score and t-distribution stochastic neighbour embedding (t-SNE) visualisation. The superiority of the proposed network is validated when compared to the imbalanced data processing method and other state-of-the-art networks, indicating that the proposed network can achieve more effective fault diagnosis under imbalanced data without data expansion and large changes to the network, providing a new feasible method for research in this direction.

Effect and mechanism of wheel–rail adhesion on torsional vibration and stability of the braking system

A high-speed train braking system with the disc–pad sliding friction pair and the wheel–rail rolling friction pair is a classic torsional system. By adopting a developed braking system torsional dynamics model, the influences of dry and wet rail surface conditions on system dynamic responses were investigated. Further, the system stability under different disc–pad friction and wheel–rail adhesion characteristics was explored and the interaction mechanism between the disc–pad and the wheel–rail sub-systems was revealed. The results indicated that the wheel–disc torsional vibration was more complicated under the wet rail surface condition. Moreover, the braking system had worse stability when the negative slope characteristics of disc–pad friction and wheel–rail adhesion were interacted.

ПРИНЦИПЫ ПОСТРОЕНИЯ И МОДЕЛИ СИСТЕМЫ АВТОМАТИЧЕСКОГО УПРАВЛЕНИЯ ВТОРЫМ ЛОКОМОТИВОМ ПРИ ВИРТУАЛЬНОЙ СЦЕПКЕ

Automatic control system model of second train locomotive at virtual assessment as well as control quality analysis approaches have been considered. The controlled value represents being calculated in train traffic process the distance between “tail” of a first train and “head” of a second one, providing traffic safety at emergency braking of a first train. This distance is called “virtual replacer length”. Formalization has been introduced allowing to account for synchronization absence at transfer of information on the coordinate and speed of a first locomotive and the control digital system work cycle of a second one. Speed and coordinate measurement errors have been considered which’re connected with lagging at information transfer and possibility of failing in decoding of received by radio channel information by second locomotive receiver. At virtual length assessment, various ways of its upper assessment have been considered, the way has been chosen, taking into account motion speeds and the coordinates of both trains, emergency braking path of a first train, the possibility of emergency braking of a first train at the beginning of the cycle of information transfer, measurement methodological and instrumental errors. Digital proportional integral differentiating control law has been considered as an operator, transforming mismatches at the choice of a control of a second locomotive. Automatic control system model has been developed which relates to impulse system class and which feature is the calculation of control action in train traffic process. The parametric synthesis of automatic control system is recommended to be held by simulation modelling methods. Control quality criteria have been chosen.

Evaluation of Braking Timing Sequence of Semi-Trailer Train Based on Fuzzy Analytic Hierarchy Process

A reasonable braking timing sequence plays an important role in the braking stability of a semi-trailer train, but there is still a lack of objective and comprehensive scientific evaluations of braking stability as shown by the braking timing sequence. Aiming at this problem, through the analysis of relevant regulations and standards at home and abroad, an evaluation index hierarchy model of the semi-trailer train braking timing sequence is constructed. The fuzzy analytic hierarchy process is used to determine the weight of the evaluation index of each level of the braking timing sequence, and a comprehensive evaluation is obtained. In order to determine the optimal braking timing sequence of the train during braking, a simulation model was established and simulated. Through the combination of index weight and simulation data, the model can provide a theoretical basis for the subsequent study of the optimal braking timing sequence of semi-trailer trains running under different working conditions.

Metro traction power measurements sizing a hybrid energy storage system utilizing trains regenerative braking

The paper describes the measuring systems and methodology for acquiring traction power measurements on the on-board traction systems of two metro trains and three 750 V DC rectifier substations in the Athens Metro Line 2. Being part of a wider investigation to develop a Hybrid Energy Storage System (HESS), the purpose of the present measurements is to provide traction systems experimental and operational data that would assist in the understanding of the dynamic characteristics of train braking regeneration and quantify the available energy that could be stored in a super-capacitors/batteries hybrid storage system for further use, which would otherwise be wasted and consumed as heat in stations and tunnels through the trains' braking resistors. In turn the stored energy could power upon demand selected stationary electrical loads in Metro stations of a non-safety critical character (such as lighting, ventilation, pumps, etc.) leading to very significant energy savings and to a corresponding reduction of greenhouse gases. Preliminary results confirm the feasibility of the energy saving concept indicating a significant potential for the hybrid energy storage devices and subsequent energy re-use of 4000–6000 kWh/day per rectifier substation of otherwise unused train braking energy, with a typical Metro station stationary loads consumption of 2000 kWh/day.

Research progress on friction and wear properties of powder metallurgy brake pad

The terrain of China is relatively complex, which leads to the complex and changeable working conditions of high-speed trains during braking. Studying the influence under different braking conditions on the performance of train brake pads is a problem worthy of in-depth discussion. In order to explore the performance changes of powder metallurgy brake pads during train braking, this paper summarizes the friction and wear properties and wear mechanism of powder metallurgy brake pads under different braking conditions; combined with the research status of powder metallurgy brake pad materials, it provides directions for the research of new powder metallurgy materials. Provide reference for the improvement of brake pads of high-speed train in the future.

Fault diagnosis for high‐speed train braking system based on disentangled causal representation learning

AbstractData‐driven methods have shown a great potential in diagnosing ongoing faults in high‐speed trains (HSTs). However, lacking enough interpretability, data‐driven methods have not been widely considered in practical operation of HST. In recent years, the rapid development of the causal discovery technology provides an effective way to improve the model interpretability. In this work, based on disentangled causal representation learning (DCRL), an effective and interpretable fault diagnosis framework is proposed for HST braking system. Independent potential factors of the high‐dimensional monitoring data are extracted by the DCRL based on factor analysis. A stable and clear causal network in the factor space is obtained based on causal discovery, and the information irrelevant to fault diagnosis can be eliminated by feature selection. With logistic regression as the fault diagnosis model, the risk importance ranking of the monitoring features can be obtained. Compared with most commonly used methods, the method proposed in this paper has high interpretability and application value, which is more conducive to the subsequent fault location and troubleshooting. Based on real monitoring data of a HST braking system, it is justified that the effectiveness of the fault diagnosis model can be significantly improved by DCRL. Moreover, the applicability of the proposed method is also discussed.

The effect of wheel polygonal wear on temperature and vibration characteristics of a high-speed train braking system

To study the effect of wheel polygonal wear (WPW) on temperature and vibration behaviours of a high-speed train braking system, a rigid-flexible coupled vehicle system dynamics model and a thermo-mechanical coupled finite element (FE) model of a braking system are developed in this study. The accuracy of the vehicle dynamics model and FE model are verified by line and bench tests, respectively. The dynamic interactions between different vehicle components, and the nonlinear factors such as wheel − rail interactions, non-linear damper and disc − block frictions are comprehensively considered in the model, which is able to more realistically reflect the service environment of a vehicle system and accurately capture the vibration, temperature and disc − block contact status of a braking system during braking process. Based on the established models, the dynamic behaviours of the braking system excited by WPW is systematically investigated. The results indicate that the standard deviation (SD) of contact area, the root mean square (RMS) values of vibration and the temperature of friction block interface with WPW are much higher compared to those without WPW. Besides, the braking system experiences more intense vibration with the increment of WPW order.

Dynamics analysis of train-track-bridge coupled system considering spatial flexibility of high piers and system longitudinal vibrations

High-pier railway bridges are mostly applied in mountainous areas. Due to the large spatial flexibility of the high piers under train dynamic loads, especially under braking conditions, the wheel-rail (WR) dynamic interaction may become more intense in the longitudinal direction, which could induce larger deformation and impact on the train-track-bridge (TTB) coupled system. To investigate the dynamic characteristics of such complex and large system during train braking condition, a 3D train-slab track-high pier bridge (TTHPB) coupled dynamics model is established and verified by considering the system longitudinal vibrations and the spatial flexibility of high piers. In this work, the influence of concerned bridge height from 60 to 160 m on the dynamic performances of the TTHPB system under train braking condition is studied. Results indicate that the operation speed has a significant effect on carbody acceleration and WR force. The longitudinal carbody acceleration due to its high-frequency vibration, as well as its noticeable amplitude induced by the long-time frequent braking, should be carefully considered in the evaluation of riding comfort index. The longitudinal dynamic behaviour of the high pier bridge is considerable and should be paid full attention to in bridge design compared with the other two directions.