High-speed Railway Vehicles Research Articles

A hybrid triboelectric-piezoelectric-electromagnetic generator with the high output performance for vibration energy harvesting of high-speed railway vehicles

With the rapid development of intelligent high-speed train, people's travel becomes more convenient, time-saving and comfortable. However, the increase in the number of equipped electronic facilities also brings more power consumption. While the ultra-high voltage drive power system cannot directly drive its numerous devices and the vibrational energy of high-speed trains is completely abandoned. Herein, a hybrid triboelectric-piezoelectric-electromagnetic generator (HTG) is proposed to drive the signal and sensing devices of high-speed train by in-situ harvesting the corresponding vibration energy. Compared with commercial polyformaldehyde film, the output power of triboelectric nanogenerator with the polyformaldehyde nanofiber film prepared by electrospinning technology is improved by 130 times. Furthermore, thanks to the high space utilization and output performance, the HTG has achieved a power-density of the order of kW/m3, which is an improvement of 1–3 orders of magnitude compared to previous research work on vibration energy collection. Importantly, the self-powered wireless motion monitoring system based on HTG can realize real-time monitoring and transmission of motion information such as speed, frequency and displacement. This finding not only gives an important way to efficiently harvest vibration energy, but also provides new ideas for the design of more economical, comfortable and intelligent high-speed trains.

Fatigue properties of non-press-fitted part of full-scale induction-hardened axles of medium-carbon steel for high-speed railway vehicles

This study aimed to examine the stress–number of cycles (S–N) curve and fatigue limit of non-press-fitted parts to improve the sophistication of the design method of induction-hardened axles for medium-carbon steel high-speed railway cars. Macroscopic cracks were generated in the non-press-fitted parts of the axles by selecting appropriate fatigue test methods. Thus, the S–N curve was approximated, and the fatigue limit was obtained. The value of an index in the power-law expression of the S–N curve was 11, which was proposed to fatigue damage evaluation standard. Moreover, we constructed a prediction model for high-and very-high-cycle fatigue limits based on the local fatigue-limit approach and fatigue test results of cut-out specimens from several depth regions of induction-hardened axles. The fatigue limit predicted by the model agrees with the experimental high-cycle fatigue limit. The model estimated that the fatigue limit did not decrease in the very-high-cycle regime.

A novel wheel wear indicator in regard to wheel-rail contact parameters and vehicle hunting stability

It is well known that the abnormal equivalent conicity caused by wheel and rail wear is the main root of hunting instability, but it is still difficult to trace the underlying factor when the dynamic instability occurs, that is, wheel wear induced, rail wear induced or both. To face this challenge problem, this paper constructed a novel wheel wear indicator based on the moved wear area difference. The long-term tracking test data of different wheel profiles were used to analyze the correlation between the wear indicators and the wheel-rail contact parameters. A fully detailed dynamic model of one typical high-speed railway vehicle was developed to investigate the evolution of vehicle hunting stability under the variation of the proposed wear indicator. The results indicate that the proposed wear indicator based on the moved wear area difference has a strong correlation with the equivalent conicity and can be used for the estimation of wheel-rail contact conditions. Furthermore, the hunting stability and the instability form is closely related to the value of the proposed wheel wear indicator, which is helpful to trace the underlying factor of hunting instability, thereby supporting intelligent operation and maintenance of railway vehicles.

Dynamic response of high-speed railway vehicle and welded turnout on large-span bridges based on rigid-flexible coupling system

Welded Turnout on Large-span Bridge (WTLB) is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway (HSR). Understanding the coupling dynamic response of the vehicle and WTLB is essential. Previous research did not consider the dynamic behavior of foundations, leading to an underestimation of the vehicle-turnout-foundation coupling dynamic response, particularly when turnouts were laid on large-span bridges. This study proposes a novel modeling method that includes the foundations, to overcome the previous shortcomings by applying a rigid-flexible coupling system. In this approach, the vehicle was modeled as a rigid body sub-model in a Multi-Body Software (MBS), while WTLB was modeled as a flexible bodies sub-model using Finite Element (FE) software. The modal information from the FE model was imported into the MBS software. The two sub-models were coupled by the wheel-rail contact in the MBS environment and then the Vehicle-turnout-bridge Rigid-flexible Coupling Dynamic (VRCD) calculation model was established and it was discovered that the calculation results showed good agreement with the field test data. Through the VRCD model, the safety of the structure, the stability of the vehicle and the comfort of passengers were investigated, as well as several important infrastructure factors. The results demonstrate that this novel method provides accurate calculations and highlights the complex and significant interactions in the vehicle-turnout-bridge system.

Design of robust active suspension system for performance improvement and vibration control of railway vehicles: An H∞andμ-synthesis perspective

The ride comfort of a high-speed railway vehicle is a significant factor in assessing its performance. Despite having sound suspension systems and efficient control algorithms, the suspension system performance deteriorates with time. Hence, in this paper, a robust active vibration control system used in railway vehicles has been proposed. For analysis, a 27-degree of freedom (DOF) model consisting of structured and unstructured uncertainties has been considered. Two different robust control techniques, [Formula: see text] and [Formula: see text]-synthesis integrated with the Kalman estimator, have been adopted. The robust stability and the robust performance of the proposed control strategies have been evaluated using the structured singular values. The time and frequency domains of the closed loop perturbed responses to random track disturbances are shown. The root mean square (RMS) values of the accelerations of the car bodies are used to compare the suggested control schemes to the passive system. The primary focus of this study is to examine the level of ride comfort provided by the railway vehicle. To achieve this, simulated findings are compared and verified against experimental data collected and reported by the Research Designs and Standards Organization (RDSO). The observational data demonstrates that the results obtained from the suggested control methods are in close agreement with the experimental findings, with a minimal disparity ranging from 2.36% to 8.81% for lateral motion and 2.84% to 6.30% for vertical motion. Also, the % improvement of RMS values with [Formula: see text]-synthesis controller confirms the enhancement of the ride comfort as compared to other techniques.

Design method for suspension parameters of high-speed railway vehicles considering uncertainties

A design method for suspension parameters is proposed to ensure the desired performance of a railway vehicle despite uncertainties. The method used in this study consists of two loops: a sub-loop, which uses parameter uncertainties to determine the minimum value of target performance, and a main loop, which optimises suspension parameters such that the minimal performance achieves Pareto optimality. Thus, by selecting a suitable Pareto solution that ensures the minimum performance is equal to or higher than the required performance, the robustness of the designed vehicle against the parameter uncertainties can be achieved. The lowest low-frequency damping ratio in the service speed range was selected as one of the design targets. The other target was the critical speed. Two wheel-rail contact characteristics were applied, considering the worst conditions for each design target. The distribution of the parameter uncertainties that minimised the vehicle performance showed distinct characteristics between the longitudinal and lateral suspension parameters, which provides useful information for the maintenance of railway vehicles. The performance analysis for 100,000 random samples shows that the vehicle performed better than the targets with a high probability despite the parameter uncertainties. Further, the simulation results using multi-body dynamics simulation software validated the viability of the proposed method.

Assessing the Fire Characteristics of Chair Materials in a New High-Speed Railway Vehicle Across Various Fire Environments

The heat release rate generated when a fire occurs in a railway vehicle is one of the most important factors when designing precautions for railway facilities such as railway tunnels. In this study, the fire characteristics of interior materials required to analyze the propagation of a fire in a new railway vehicle were identified via an experimental method. The fire characteristics of the main interior materials across various radiant heat fluxes were analyzed, and the ignition temperature of the interior materials was predicted using the heat release rate and ignition time. By predicting the ignition temperature, the critical heat flux and ignition temperature were confirmed to be low for the flooring of the main interior materials. The derived fire characteristics (ignition temperature and heat release rate) for each material can be used to analyze the fire propagation phenomenon in railway cars.

Development of laser-arc hybrid welding process of butt joint for bogie pipe crossbeam components

High-speed railway vehicle bogies are the main load-bearing components, which are welded together from steel plates and tubes. Butt joint and T-joint are the main types and the joint thickness is between 8–20mm. The stability of laser-arc hybrid welding (LAHW) process correlated strongly with keyhole behaviour. In this paper, the common quality defects in full penetration root pass by LAHW were analysed. Controlling the root gap is adopted to stabilize the keyhole, to improve the stability of weld quality. A novel type of butt joint with micro structure based on Y-shaped grooves has been designed, to meet both the requirement of controlling root gap and industrial large-scale batch production. Two new structure parameters, 2 mm of the remaining blunt edge thickness and 0.3 mm of the half width of root opening, were proved by the flat plates welding test. Finally, the joint with micro structure and the root pass welding parameters were transferred to the welding process of tube crossbeam components. The LAHW process verification was completed, and the test results showed the process meets the requirements of ISO 15614.

Dynamic analysis of ultra-low frequency carbody swaying for a high-speed rail vehicle: Causes and measures

This paper investigated on the ultra-low frequency carbody swaying (ULFCS) of a high-speed railway vehicle through field tests and numerical simulations. In the field tests, the vibration characteristics, the dynamics performance, the wheel-rail contact condition, and the track condition were analyzed to realize the manifestation as well as the possible cause of this abnormal vibration. The excessive low equivalent conicity caused by the abnormal wheel tread wear arouse suspicion for this issue. To find out the mechanism and propose the solving measures, the multi-body dynamic (MBD) model of the high-speed vehicle was developed and verified by applying the measured wheel/rail profiles and carbody acceleration. Based on the developed model, the linearized and nonlinear researches were performed. The results indicate that the carbody hunting, caused by the frequency coupling between the hunting mode and the carbody lower sway mode, is the deep reason of the ULFCS, and this issue can be solved by increasing the equivalent conicity and decreasing the roll stiffness of the anti-roll torsion bar. Furthermore, the ULFCS can pose a potential threat to running safety once the violent carbody swaying gives rise to the wheel-rail contact point entering the wheel flange area. Finally, the optimized measures that reducing the hardness of the abrasive block, changing the working mode of the tread cleaning device, and decreasing the anti-roll stiffness were proposed and verified by the on-track test.

Cavitation induced hydraulic yaw damper failure and its effect on railway vehicle dynamic stability

Hydraulic yaw damper (HYD) is an important suspension component that ensures the safe and stable operation of high-speed railway vehicles. However, HYD experiences the performance degradation and failure during service. Recent research found that the cavitation in HYD can affect vehicle stability by deteriorating the dynamics performance of HYD. To reveal the influence mechanism and quantify the effect extent of cavitation on hunting stability, this study delves into the cavitation phenomenon in HYD through theoretical modeling, numerical simulation and experimental validation. Considering the gas phase composition in hydraulic oil and the dynamic process of each phase transformation, a multi-phase interaction dynamic model of the hydraulic oil was originally proposed. Based on this sub-model, the physical parametric model of the HYD was established and integrated into the vehicle system as an advanced force element to study the effect of cavitation on vehicle hunting stability. The results indicate that cavitation can lead to insufficient damping force in the extension or compression stroke of HYD, subsequently affecting the vehicle hunting stability. Comparing the effects of different initial gas content on bifurcation characteristics and hunting frequency, it is observed that an increase in initial gas content results in a decrease in both linear and nonlinear critical speeds, changes in the bifurcation type and an increase in the hunting frequency. Furthermore, this effect is nonlinear, exhibiting sensitive ranges and saturation values. To ensure operational stability of high-speed vehicles, measures should be taken to prevent cavitation in HYD.

Study on dynamic performance of high-speed railway vehicle using roller rig and numerical simulation

The development of high-speed trains has increased the demand for dynamic vehicle tests on roller rigs. This study presents a nonlinear multi-body dynamic model of a vehicle system running on a roller rig and an actual track. Dynamic tests for a high-speed vehicle were performed using a full-scale roller rig to validate the numerical model. The hunting stability characteristics of the vehicle were investigated by performing a comparative analysis of the roller rig tests and numerical simulations of the vehicle on roller rigs and tracks. The results indicate that the critical hunting speed of the vehicle on a roller rig is lower than that on a track, particularly under significantly high or low equivalent conicity and yaw damper failure conditions. The characteristics of the hunting stability, riding performance, and lateral acceleration of the bogie frame were comparable in both rig tests and line operations, exhibiting consistent trends under the normal operation of the suspension system with the wheel/rail matches existing within the ideal range of equivalent conicity. However, the lateral acceleration or lateral Sperling index of the carbody could better detect the carbody hunting under low equivalent conicities, particularly when the lateral acceleration of the bogie was not sufficiently effective.

Study on mechanism of radial long cracks propagation on sliding surface of wheel brake discs

A long radial crack with a length of more than 60 mm was observed near the bolt hole of the brake disc of high-speed railway vehicles. It is necessary to study its causes and propagation mechanism. In this study, the gradient change of grain size was studied by microscopic observation of the brake disc after service. Through a variety of tensile tests, a relationship describing the gradient distribution of mechanical properties of materials was established. The radial crack propagation at the bolt hole of the friction surface was analyzed by using the extended finite element model (XFEM). The final crack lengths at the initial speeds of 250 km/h and 350 km/h are 32 mm and 43 mm, respectively. The reduction of material strength on the sliding surface and the stress concentration near the bolt hole make the crack propagate rapidly. The crack length increases with the decrease of residual strength. Cracks may continue to expand to the core through fatigue propagation, eventually leading to fatigue failure. It is proposed that the hot spot area around the bolt hole should be the key area for checking cracks during operation and maintenance.

Parameters optimum of multiple underframe suspended equipment on high-speed railway vehicle carbody vibration control by using an improved genetic algorithm

Carbody vibration control and ride comfort improvement are important research parts of high-speed railway vehicle dynamic. The effectiveness of utilizing carbody underframe suspended equipment as dynamic vibration absorbers for carbody vibration suppression has been validated. While previous research has focused mainly on a single suspended equipment without considering its vibration tolerance, a balance must be struck between reducing carbody vibration and maintaining equipment performance. To address the challenging, a multi-objective and multi-parameter optimization method is employed, integrating an improved niche genetic algorithm (INGA) into the numerical simulation process. Considering carbody flexible and multi-suspended equipment, a rigid-flexible dynamics model of a high-speed railway vehicle is established and validated on a vehicle dynamics test rig. Based on the numerical analysis, the optimal parameter combination of the stiffness and the longitudinal installation position is obtained from an evaluation function that comprehensively assesses the vibration performance of both the vehicle carbody and the equipment. Comparative analysis between the results obtained from the optimal and primitive parameters demonstrates that the optimization process not only achieves significant improvements in carbody vibration reduction but also effectively controls equipment vibration within reasonable limits. The multi-objective and multi-parameter optimization method applied on carbody underframe suspended system proves to be valuable in improving the dynamic performance of high-speed railway vehicles.

Parameter optimization of multi-suspended equipment to suppress carbody vibration of high-speed railway vehicles: a comparative study

ABSTRACTParameter optimization of equipment suspended under the carbody underframe is one of the important measures to suppress carbody vibration of high-speed trains. Previous work focused on using one equipment as a dynamic vibration absorber to control carbody vibration, overlooking the coupling effects of multiple equipments and their vibration tolerance. To address this, a comprehensive study involving multi-objective and multi-parameter optimization to enhance both carbody and equipment vibration performance is proposed. First, a theoretical model with one equipment is established to derive optimal parameters, and a simulation model with multi-suspended equipment is built to conduct optimize calculations with an improved niche genetic algorithm (INGA). Afterwards, a comparative study on carbody and equipment vibration performance is analysed based on the optimal parameters, proving that the optimal method with INGA is more effective in improving vehicle performance. Finally, the method is applied to a newly designed vehicle, and the performance is validated on a rig, providing technical support for the design of high-speed vehicles.

Suspension parameters for low-damped carbody oscillation of high-speed railway vehicle

This study presents an optimization method to design the suspension properties associated with low-damped carbody oscillations for high-speed railway vehicles. In this method, the least damping ratio for the low-frequency modes in the entire service speed range and the critical speed for a worn wheel are proposed for the design objectives. Based on the linearized vehicle model, a genetic algorithm is applied to determine the optimal suspension properties to maximize the least damping ratio while maintaining the critical speed above the desired speed. The optimization results show that the proposed method can enhance lateral ride comfort by eliminating the region where the least damping ratio of the carbody mode decreases excessively and securing a constant for the entire service speed range. The least damping ratio was improved from approximately 5.7% to 15.6% and the critical for the worn wheel increased from approximately 430 to 499 km/h. Parametric studies are conducted to investigate the influence of the tolerances of the suspension properties, and the results provide useful information regarding the manufacture of suspension elements and assembly of the bogie system. The validity of the optimized suspension properties is verified from the simulation results using railway vehicle dynamics software.

Estimation of wheelset equivalent conicity using the dual extended Kalman filter

This paper presents the implementation of the dual extended Kalman filter (DEKF) to estimate wheelset equivalent conicity, an accurate understanding of which can facilitate the implementation of an effective model-based estimator. The estimator is developed to identify the wheelset equivalent conicity of high-speed railway vehicles while negotiating a curve. The designed DEKF estimator employs two discrete-time extended Kalman filters combining state and parameter estimators in parallel. This estimator uses easily available measurements from acceleration sensors measuring at axle boxes and a rate gyroscope measuring bogie frame yaw velocity. Two tests, including linearized and actual wheel-rail geometry, are carried out at a speed of 250 km/h with stochastic and deterministic track features using multibody simulations, SIMPACK. The results with acceptable estimation errors for both track conditions indicate adequate performance and reliability of the designed DEKF estimator. They demonstrate the feasibility of utilizing this DEKF method in rail vehicle applications as the knowledge of time-varying parameters is not only important in achieving an effective estimator for vehicle control but also useful for vehicle condition monitoring.

Active vertical vibration suppression of high-speed railway vehicles by controlling internal pressure of the air spring using μ-synthesis control

In recent years, railway vehicles have become lighter since it corresponds not only to the improvement of the running speed but also to the reduction of running cost and environmental noise. On the other hand, this causes an increase in the vertical elastic vibration of the car body and the riding comfort has deteriorated. Therefore, various strategies to reduce vertical vibration have been studied. In this study, vertical vibration reduction, by controlling the internal pressure of the air spring using µ-synthesis control, is proposed. The merit of µ-synthesis control is that it can guarantee robust performance. A controller by µ-synthesis was designed for vibration reduction of a 1/6 scale railway model and compared nominal performance and robust performance with H∞ control theory. Moreover, a feasibility study of this strategy was investigated for full-scale railway vehicles through simulation.

Optimizing Friction Block Location on Brake Pads for High-Speed Railway Vehicles Using Artificial Neural Networks

Brake discs play a crucial role in braking railway vehicles, but the frictional heat generated during the braking process can lead to high temperatures on the disc. Changes in the friction block location on the brake pad result in variations in the temperature distribution across the brake disc. This study aims to optimize the positioning of friction blocks on the brake pad using artificial neural networks (ANN) and the Design of Experiments (DOE) approach based on the Taguchi methodology. The primary objective of this study is to mitigate temperature discrepancies in the frictional heating rate among distinct sectors along a radius from the center of the brake disc. To analyze the temperature variations caused by frictional heat, finite element analysis (FEA) is executed to account for the thermomechanical characteristics of the brake disc. The optimized brake pad, obtained through the ANN, is evaluated based on the temperature and thermal stress applied to the brake disc. The optimized model displays a larger hot band on the brake disc compared to the original model, leading to a more even distribution of thermal stress across the brake disc. In conclusion, the use of optimized pads offers significant performance benefits, resulting in a reduced maximum temperature and thermal stress, thus improving the overall braking performance of railway vehicles.

Research on high-speed railway vehicle emergency braking control based on rail surface foreign matter identification

In order to improve the operation stability of high-speed railway vehicles, an emergency braking control method for high-speed railway vehicles based on the identification of foreign matters on the track surface is proposed. The dynamic frame scanning method is used to build the image acquisition of abnormal objects on the high-speed rail track surface, and the visual sensor and vibration sensor are used to identify and process the features of foreign objects on the high-speed rail track surface. According to the abnormal feature extraction results, the command signal in case of foreign objects is transmitted to the terminal command library of the braking control system. According to the transfer switch of the emergency braking system to display the main emergency disposal output states such as the train emergency disposal information reception, emergency disposal level, emergency disposal type and other information, the joint control method of contact pressure distribution and non-uniform heat flux is adopted, and the joint control method of control system, drive system, disc friction system and signal acquisition system is adopted. The emergency braking control module is established to realize the emergency braking control of high-speed railway vehicles according to the feature recognition results of foreign matters on the rail surface. The test results show that the control module is less affected by the vehicle wheelbase characteristics, track structure characteristics and other factors when using this method for high-speed railway vehicle emergency braking control, and has a strong ability to identify the characteristics of foreign matters on the track surface, which improves the stability and real-time performance of emergency braking.

Thermal insulation performance and dynamic response of anti-freeze subgrade of high-speed railway in seasonally frozen regions

In order to counteract the adverse effects of seasonally frozen regions, measures need to be taken to insulate high-speed railway subgrades and implement anti-freeze structures. The present study delves into this topic by analyzing the thermal–mechanical behaviors of railway subgrade through on-site measured data. Then, using the hydrodynamic theory, a model of frozen soil with Multi-physical field coupling is built, on which the temperature field and frost heave development of six different subgrade structures are explored, and produces a vehicle-track-subgrade coupling dynamic model that is used to calculate the dynamic performance of vehicles and the dynamic response transfer between subgrade layers under the influence of different anti-freeze subgrade structures. The results show that the subgrade structure built using concrete insulation (asphalt concrete (AC) or cellular concrete (CC)) + cement stabilized crushed stone (CSCS) + polyurethane (PU) panel mitigates the impact of external air temperatures and internal cooling, helping to reduce the maximum frost heave while simultaneously achieving improved thermal insulation. Further, these anti-freeze subgrade structures also bolster the safety and stability of high-speed railway vehicle operations. Therefore, it is suggested that the “concrete insulation layer + CSCS layer + PU panel” structures be utilized as a reference during the design of subgrade structures in seasonally frozen regions.