High-speed Train Research Articles

Intelligent spare ordering and replacement optimisation leveraging adaptive prediction information

Predicting system health using inspection technologies is crucial for efficiently managing the maintenance of various industrial products. This study introduced an innovative policy for intelligently ordering and replacing spare parts. It utilises real-time prediction data to make sequential decisions on whether to schedule spares and when to conduct non-immediate maintenance. A generalised non-linear stochastic process was established to capture the underlying degradation path, with a lifetime coefficient updated through Bayesian inference. Conditional reliability assessed during regular inspections determines when spare preparations and delayed replacements are warranted. Predictive replacements can also be postponed based on the expected remaining lifetime adjusted for safety factors and spare lead times. The model dynamically optimises operational costs by iteratively optimising spare-ordering times, postponement intervals, and adjustment coefficients. Numerical experiments on high-speed train gearboxes validated its superior cost-effectiveness compared to conventional approaches.

Effect of wing height layout on the aerodynamic performance ofhigh-speed train

PurposeThis paper aims to investigate the effect of different wing height layouts on the aerodynamic performance and flow structure of high-speed train, in a train-wing coupling method with multiple tandem wings installed on the train roof.Design/methodology/approachThe improved delayed detached eddy simulation method based on shear stress transport k-ω turbulence model has been used to conduct computational fluid dynamics simulation on the train with three different wing height layouts, at a Reynolds number of 2.8 × 106. The accuracy of the numerical method has been validated by wind tunnel experiments.FindingsThe wing height layout has a significant effect on the lift, while its influence on the drag is weak. There are three distinctive vortex structures in the flow field: wingtip vortex, train body vortex and pillar vortex, which are influenced by the variation in wing height layout. The incremental wing layout reduces the mixing and merging between vortexes in the flow field, weakening the vorticity and turbulence intensity. This enhances the pressure difference between the upper and lower surfaces of both the train and wings, thereby increasing the overall lift. Simultaneously, it reduces the slipstream velocity at platform and trackside heights.Originality/valueThis paper contributes to understanding the aerodynamic characteristics and flow structure of a high-speed train coupled with wings. It provides a reference for the design aiming to achieve equivalent weight reduction through aerodynamic lift synergy in trains.

Microstructure and fatigue properties of laser-MIG hybrid welding of medium-thickness 6005A aluminum alloy

Light alloys represented by aluminum alloys have a wide range of applications in railway transportation, the key load-bearing parts of high-speed train bodies are welded with a large number of medium-thickness plates, so the study of the welding performance of medium-thickness aluminum alloy plates is significant. In this study, laser-MIG hybrid welding technology is used to realize the single-layer, single-pass welding of 6005A aluminum alloy plate with a thickness of 10 mm. The grains in the weld zone (WZ) are coarsened by welding heat, and the average diameter is about 1.6 times that of the base metal (BM), while the average grain diameter in the heat-affected zone (HAZ) is similar to that of the BM. A softening phenomenon is observed in the welded joint, with a minimum hardness of 72.6 HV in the HAZ. TEM analysis shows that the softening phenomenon is caused by the coarsening of precipitate phases in the HAZ. In terms of tensile properties, the ultimate tensile strength (UTS) of the welded joint is approximately 237 MPa, which is 70.1 % of the BM. The fatigue strength (Nf = 2 × 106 cycles) of the welded joints is predicted to be 83 MPa, which is 64 % of the yield strength (YS), from the S-N curve obtained by fitting the tension–compression fatigue test data. Different morphologies of secondary phase particles are observed in the fatigue crack propagation zone, and their formation and effects on secondary crack are described. The fracture location indicates that softening behavior in the HAZ is the main factor influencing tensile performance, while defects in the WZ are the primary factors affecting fatigue fracture. The experimental results can enrich the tensile and compressive fatigue data of 6005A aluminum alloy.

Numerical Analysis on The Aerodynamic Performance of A High-speed Train Operating on Various Embankment Heights Under The Influence of Crosswinds

Given the unavoidable geographical surface, railings must be raised above ground level in some cases, which is known as an embankment. It was discovered that the height of the embankment had a significant influence on the slipstream on the train's leeward side especially during crosswind conditions. The primary objectives of this study were to investigate the impact of varying embankment heights on the aerodynamic characteristics of a high-speed train under different crosswind conditions using computational fluid dynamics (CFD) analysis. The German Aerospace Center DLR's Next-Generation High-speed Train (NG-HST) model has been used for this study. The yaw angles (ψ) are ranging from 10° to 50° in 10° increments. The Reynolds number based on the model's height and freestream velocity at the computational domain is 1.3 x 106. In the results, it shows that embankment height and crosswind ψ has a significant impact on the aerodynamic characteristics. Essential aerodynamic parameters that have a significant impact on train stability, such as the drag, lift, and side force coefficients, as well as the roll, yaw, and pitch moment coefficients, revealed that the higher the ψ, which included 40° and 50°, produced poor results compared to the lower ψ, which included 10°, 20°, and 30°. In terms of visual appearance, rising of crosswind angles have a greater impact on the formation of vortices on the leeward side of the train body and embankment. Thus, it can be concluded that the embankment heights and crosswind angles are crucial in determining train safety operations.

Effects of post heat treatment on key T-phase evolution and the matching mechanism of enhanced strength-toughness, wear resistance and corrosion resistance in Al-Mg-Zn-(Cu-Er-Zr) alloy by laser powder bed fusion

Al-Mg-Zn-(Cu-Er-Zr) system alloy is a novel alloy designed by materials genetic method for laser additive manufacturing of lightweight brake discs and the T-phase (T-AlMgZnCuZrEr) in this alloy is the most important microstructure for enhancing performance matching of the alloy. Scientifically regulating the T-phase evolution through innovative preparation processes to improve the matching of strength-toughness, wear resistance, and corrosion resistance in this novel alloy is the fundamental work for preparing high-performance lightweight high-speed train brake disc parts using laser additive manufacturing. In this work, laser powder bed fusion and post heat treatments were employed to prepare Al-Mg-Zn-(Cu-Er-Zr) alloy samples with the superior matching of strength-toughness, wear resistance and corrosion resistance, and the key T-phase evolution and performance enhancement mechanisms of the samples were studied. The results indicate that post heat treatments significantly influenced the quantity, size, and structure of the T-phase in the cladded sample, which significantly enhanced the strength-toughness, wear resistance and corrosion resistance matching of the alloy. It is found that under the optimized aging treatment at 200 °C/6 h, due to the evolution of T-phase area fraction and cell-like structure inside the T-phase, the strength-toughness, wear resistance and corrosion resistance were improved by 30 %, 28 %, 1.4 %, respectively. The precipitation and concave dissolution mechanisms of the T-phase during post heat treatment have been finely revealed, and a three-performance matching relationship model has been successfully constructed based on the strength-toughness matching equation. A new laser powder bed fusion followed by the aging process to manufacture an Al-Mg-Zn-(Cu-Er-Zr) alloy sample with the superior matching of strength-toughness, corrosion resistance, and wear resistance has been obtained, which provides a valuable reference for laser additive manufacturing high-performance lightweight aluminum alloy brake disc parts.

The braking performance and failure mechanism of copper-based brake pads during repeated emergency braking at 400 km/h

Copper-based brake pads have played a pivotal role in the braking systems of commercial high-speed trains travelling at speeds ranging from 200 to 350 km/h. In this study, the braking performance and friction and wear mechanism of copper-based brake pads at 400 km/h were further evaluated using a full-scale dynamometer. The results show that under repeated emergency braking conditions at 400 km/h, the mean friction coefficient can be maintained at about 0.3 and remains stable within six braking cycles. Subsequently, a fade phenomenon in the mean friction coefficient emerges accompanied by a significant increase in braking distance, while the mean wear loss is relatively high throughout the entire testing process. Microstructural characteristics of the friction film and matrix indicate that strong oxidation plays an important role in the failure process of the brake pads. The friction film primarily composed of oxides exhibits numerous defects, which are susceptible to peeling off during braking, thereby compromising wear resistance. Additionally, as the braking cycles accumulate, oxidation gradually invades and weakens the matrix, leading to violent migration of the copper-rich friction film across the friction interfaces and resulting in the deterioration of friction performance. This work provides valuable insights into the failure behavior of copper-based brake pads at higher braking speeds and can provide potential direction for further improving their performance.

ANALISIS SENTIMEN KEPUASAN PELAYANAN TRANSPORTASI ONLINE GOJEK MENGGUNAKAN ALGORITMA EXTREME LEARNING MACHINE

With the rapid advancement of technology, online transportation has become the main solution for many people in Indonesia to travel easily and efficiently. Companies such as GOJEK are constantly innovating to improve their services, resulting in many responses and reviews from users. This research aims to analyze customer satisfaction with these online transportation services by analyzing the sentiment of user opinions on the Twitter platform. Sentiment analysis plays a very important role in decision making by classifying user reviews. Data was retrieved through a crawling process using specific keywords related to each service. The data preprocessing process includes case folding, tokenizing, normalization, stemming, filtering, and convert negation. This aims to clean and prepare the data so that it can be processed using the algorithm better. This process includes removing irrelevant elements from the text data, converting the text into a consistent or more standardized form, reducing the number of features in the data by stemming, and converting the text into numbers or vectors so that it can be processed by the algorithm. Feature extraction is performed using the Word2Vec model to convert text into a numerical vector representation that can later be processed by ELM. Converts words into numeric vectors in a high-dimensional space, where words that have the same context in the text are close to each other in that space. The ELM (Extreme Learning Machine) algorithm is used as a classification model due to its high training speed and good generalization ability. Model evaluation is done using confusion matrix which measures classification performance through accuracy, precision, recall matrix. The results of this study show that the ELM algorithm with Word2Vec feature extraction is able to classify user sentiment with a high level of accuracy. This research provides insight into user satisfaction with online transportation services and can be a reference for companies to improve their service quality

Advancing high-speed train gearbox durability: enhanced bearing load and contact stress through transition from helical to herringbone gears

High-speed trains typically utilize helical gear transmissions, which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings. This paper focuses on the gearbox bearings, establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains. The modeling particularly emphasizes the precision of the bearings at the gearbox’s pinion and gear wheels. Using this model, a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions. The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear, and this imbalance intensifies with the increase in train speed. Consequently, this results in a significant increase in contact stress on the bearings on one side. The adoption of herringbone gear transmission effectively suppresses axial forces, resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings. The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings, thereby extending their service life.

A robust optimisation approach of train timetabling for freight transportation using high-speed railway

To ensure reliable services for high-speed freight rail transport, we address the issue of robust freight train timetabling by incorporating buffer times. Unlike passenger trains with prescribed timetables, high-speed freight train timetables need to be scheduled from the beginning and integrated into existing passenger schedules. To achieve reliable high-speed rail freight services, we introduce robust parameters that determine the buffer times for train operations and station stops. Using these, we develop an integer linear robust model aimed at maximizing timetable robustness, considering given control parameters, while minimizing travel and deviation times. We employ an integer Benders decomposition algorithm to solve this model efficiently. Our robust optimization method is validated through experiments using data from the Chengdu-Chongqing high-speed railway, demonstrating the efficacy and efficiency of our model and algorithm, especially in balancing efficiency and robustness.

High-speed trains in Japan in the years 2002–2020

High-speed trains are the most modern and advanced technology for moving passengers in land transport. Their main advantage is that they achieve high speeds, usually from over 200 to 300 km/h, which significantly shortens the travel time in relation to the time needed to cover the same distance by conventional trains. The article presents the development of high-speed rail in Japan, an island country located within the ring of fire of the Pacific. The analysis of the technical condition and the stages of historical development of high-speed railways were preceded by an assessment of the economy and transport as well as a study of transport intensity. The summary of the article includes the effects and benefits of using high-speed rail, as well as methods of financing and plans for further development.

Circular Steel for Fast Decarbonization: Thermodynamics, Kinetics, and Microstructure Behind Upcycling Scrap into High-Performance Sheet Steel

Steel production accounts for approximately 8% of all global CO2 emissions, with the primary steelmaking route using iron ores contributing approximately 80% of those emissions, mainly due to the use of fossil-based reductants and fuel. Hydrogen-based reduction of iron oxide is an alternative for primary synthesis. However, to counteract global warming, decarbonization of the steel sector must proceed much faster than the ongoing transition kinetics in primary steelmaking. Insufficient supply of green hydrogen is a particular bottleneck. Realizing a higher fraction of secondary steelmaking is thus gaining momentum as a sustainable alternative to primary production. Steel production from scrap is well established for long products (rails, bars, wire), but there are two main challenges. First, there is not sufficient scrap available to satisfy market needs. Today, only one-third of global steel demand can be met by secondary metallurgy using scrap since many steel products have a lifetime of several decades. However, scrap availability will increase to about two-thirds of total demand by 2050 such that this sector will grow massively in the next decades. Second, scrap is often too contaminated to produce high-performance sheet steels. This is a serious obstacle because advanced products demand explicit low-tolerance specifications for safety-critical and high-strength steels, such as for electric vehicles, energy conversion and grids, high-speed trains, sustainable buildings, and infrastructure. Therefore, we review the metallurgical and microstructural challenges and opportunities for producing high-performance sheet steels via secondary synthesis. Focus is placed on the thermodynamic, kinetic, chemical, and microstructural fundamentals as well as the effects of scrap-related impurities on steel properties.

Effect of geometry simplification and boundary condition specification on flow field and aerodynamic noise in the train head and bogie region of high-speed trains

Effect of geometry simplification and boundary condition specification on flow field and aerodynamic noise in the train head and bogie region of high-speed trains

Visual localization and quantitative detection method for thermal defects in cable terminals of high-speed trains based on a temperature derivative

Abstract Cable terminal defect detection plays an important role in ensuring the safe and stable operation of high-speed trains (HST). In this paper, a numerical model of the electromagnetic thermal field of overheating defects of cable terminal shielding grids and a method of detecting internal defects of cable terminals - even-order temperature derivative (EOTD) is proposed for quantitative detection of internal defective structures of vehicle-mounted cable terminals. Firstly, a numerical model of the electromagnetic thermal field of cable terminals under the condition of leakage current is constructed, through which the temperature field distribution characteristics of different defective structures are analyzed. Then, the intuitive location of the defective region is obtained by investigating the derivative characteristics of the temperature image, and the depth and intensity of the defects are quantitatively assessed by using the main side peak (MSP) distances and the MSP values extracted from the derivative curves. Finally, the simulation and experimental results achieve the identification of defect structures and the quantitative detection of defect depth and intensity, proving the effectiveness and accuracy of the proposed method.

National economic benefits through high-speed train services: The role of service quality and quality pursuer on client satisfaction

National economic benefits through high-speed train services: The role of service quality and quality pursuer on client satisfaction

Mechanical and microstructure characterisation of 2.5D C/C-SiC composites applied for the brake disc of high-speed train

Carbon fibre reinforced silicon carbide (C/C-SiC) composite materials have attracted increasing attention in brake system of high-speed trains, due to their low density, high specific strength, thermal stability, and frictional wear performance. This study aims to explore the mechanical properties of the 2.5D C/C-SiC composites, in order to characterise its potential application to the friction braking system of high-speed trains. To comprehensively evaluate the mechanical performance of the 2.5D C/C-SiC composites, the chemical vapor infiltration (CVI) method was adopted to prepare novel samples with high densification and low content of residual Si. The mechanical properties and failure mechanisms of the composites were investigated under various loading conditions, including tension, compression, bending, and shear tests. The experimental results indicated that the 2.5D C/C-SiC composites exhibited superior mechanical properties, with average in-plane tensile strength, compressive strength, bending strength, and interlaminar shear strength reaching 127.67 MPa, 326.92 MPa, 355.74 MPa, and 9.77 MPa, respectively, which are 2–8 times higher than the mechanical properties of C/C-SiC composites in existing publications. Under different loading conditions, the composites demonstrated characteristics of ductile fracture, pseudo-plastic compression fracture, pseudo-plastic bending fracture, and brittle shear fracture. Both high fibre content and the formation of SiC structure were advantageous for enhancing the load-bearing performance of C/C-SiC composites. The outstanding mechanical properties of the 2.5D C/C-SiC composite render the brake disc highly resistant to deformation and cracking under high stress, thereby enhancing its durability and establishing it as the ideal material for the next generation of high-speed train brake discs.

An improved delayed detached-eddy study on the aerodynamic braking technique based on blunting the streamlined section of the high-speed train

This paper utilizes the improved delayed detached-eddy simulation method to investigate an aerodynamic braking technique involving blunting the streamlined portion of a high-speed train (HST) at Re = 5.0 × 105. The accuracy of the numerical simulation method was validated through reduced-scale wind tunnel experiments at the same Reynolds number level. The study compares aerodynamic drag, pressure distribution, boundary layer, and wake flow characteristics between the original configuration and the braking configuration of the HST. Additionally, the impact of aerodynamic braking plates on the flow characteristics around the key components of the HST has also been discussed. The results indicate a significant increase in the pressure drag experienced by the HST with the application of aerodynamic braking plates to its streamlined sections, while there is a slight decrease in viscous drag. This leads to a remarkable 235.4% rise in the overall aerodynamic drag of the entire HST. The aerodynamic braking plates also have a substantial impact on the turbulent wake flow topology, significantly increasing turbulence levels in the near-wake region. Furthermore, the implementation of aerodynamic braking plates may affect pantograph current collection by significantly altering stream-wise and vertical velocity components, notably increasing velocity fluctuation around the contact position between the pantograph and power supply lines.

Optimization of the cruising speed for high-speed trains to reduce energy consumed by motion resistances

As one of the effective measures to reduce energy consumption of high-speed railway, train operation control has gained much attention because of its cost-effectiveness. Conventional approaches to eco-driving generally rely on single-mass train models and lack a thorough investigation into the vehicle cruising process, which can overlook real-world operation conditions and hinder further improvements in energy efficiency. To address these issues, this paper proposes a comprehensive framework for optimizing the cruising speed of high-speed trains (HSTs) based on track conditions to reduce energy consumed by motion resistances (ECMR). Firstly, a multibody dynamics simulation model of the HST is developed and validated to accurately evaluate ECMR under a range of operation scenarios. Simulation results show that the impact of speed on ECMR varies considerably according to track characteristics. Subsequently, a neural network is constructed to derive the regressive relationship between operation conditions and ECMR. On this basis, an optimization model for the cruising speed under different track conditions is formulated to minimize the ECMR of a railway segment with a given operation time. Finally, the effectiveness of the model is validated through case studies, which demonstrate that ECMR can be reduced by up to 27.85% compared to traditional control strategies. The proposed optimization method can be integrated with current train speed profiles to further enhance energy efficiency. This framework has broad applicability for addressing engineering problems related to train operation optimization.

Three-dimensional trajectories of irregular-shaped tunnel lining fragments in the flow environment caused by high-speed trains

High-speed railway tunnel lining fragments can cause collisions with trains and track blockages, severely affecting train operation. When a train passes through a tunnel where lining fragment is likely to occur, the train wind effect may significantly affect the trajectory of the lining fragment, making the location where the lining fragment is difficult to predict. For safety purpose, this study aims to analyze the impact of the initial circumferential position and shape of irregular-shaped lining fragments on their aerodynamic performance. Using on-site scanning and mathematical statistical methods, the shape characteristics and probability distribution of actual lining fragments in the tunnel are obtained. The aerodynamic behavior of irregular-shaped lining fragments with different initial positions and three typical aspect ratios (ARs) are investigated based on the overset grid method and the dynamic fluid–body interaction model framework as a high-speed train passes. The study found that the most representative lining fragments with an AR of three have a mass of 1.5 kg and are located 2.5 m from the tunnel centerline. The flight behavior of lining fragments shows distinct three-dimensional features, with both translation and rotation significantly affected by the aerodynamic effects of the train and the geometric shape of the fragments. The longitudinal and lateral translational distances of lining fragments at the top of the train decrease as their initial position moves further from the tunnel's centerline. With an increase in AR, both the longitudinal and lateral flight distances and average flight velocities of the fragments increase. The macroscopic flow field within the tunnel directly influences the motion characteristics of the lining fragments. Complex flow separation and circulation phenomena near the fragments result in uneven pressure differences acting on the smooth and rough surfaces of the lining fragments, causing irregular motion. The conclusions of this study provide a theoretical basis for assessing and preventing the impact of lining fragments on the operational safety of trains.

Effects of combined-type wind barriers on the aerodynamic characteristics of train–bridge system for a long-span suspension bridge

The development tendency of lightweight and higher-speed regarding trains goes against the safety and comfort requirement of high-speed trains, especially in the scenario of the train running on bridges within crosswind environments. Wind barriers have been proven to be an effective measure to guarantee the train's operation security. In this paper, a new type of wind barrier consisting of the fence-type wind barrier form and open hole-type wind barrier form has been proposed. Then, a series of wind tunnel tests about the large-scale section model of a large-span suspension bridge installed with different wind barriers have been conducted. The effects of three different forms of wind barrier including fence-type, open hole-type, and combined-type on the aerodynamic characteristics of the train-bridge system have been analyzed. The windproofing effectiveness and the protection mechanism of the combined-type wind barrier on the train-bridge system have been revealed through the measured aerodynamic characteristics. The results show that the installation of open hole-type, fence-type, and combined-type wind barriers at a height of 4 m and a ventilation rate of 19% yields a maximum reduction in the train drag coefficient of 67.70%, 72.92%, and 97.21%, respectively. Moreover, the combined-type wind barrier can improve the train-bridge system's aerodynamic performance and trains' running safety on bridges when comparing with the open hole-type and fence-type wind barriers. The proposed combined-type wind barrier can provide a more efficiency and practical way for the high-speed train's running safety on the bridge.

Improved delayed detached-eddy simulation on aerodynamic characteristics of biomimetic Coleoptera pantograph deflectors installed on a high-speed train

Improved delayed detached-eddy simulation on aerodynamic characteristics of biomimetic Coleoptera pantograph deflectors installed on a high-speed train