Rail Vehicles Research Articles

Concept for an innovative screw coupling system production process

The article presents the concept of an innovative approach to the production of a screw coupling system, a key element in rail vehicles. The use of ready-made components from various subsuppliers, combined with new quality control methods, offers an opportunity for a significant reduction in cost and production time while increasing the efficiency and flexibility of the process. Key stages of the production process are highlighted, from the selection of semifinished products, through quality control, to the final assembly and validation. The applied strategies can minimise waste, increase material efficiency, and have a positive impact on the environment. This study constitutes a significant contribution to the development of sustainable production in the railway industry, with an emphasis on organisational, process, and product innovations.

Development of a New Vertical Dynamic Model of a Rail Vehicle for the Analysis of Ride Comfort

The rail vehicle industry wants to produce vehicles with higher speeds, to maintain and increase its market share. However, when the speed of the vehicle increases, it may have an undesirable effect on ride comfort, in terms of ride dynamics. Recent developments towards lighter and faster vehicles make the problem of ride comfort at higher speeds increasingly important. Focusing on the behavior of flexible rather than rigid body behavior should not be neglected when designing long and light car bodies. There are several approaches to incorporate body flexibility in multibody simulations and they have some superiorities and weaknesses. In this study, an efficient and accurate vertical dynamic model for the ride comfort analysis is developed and implemented in a commercial object-oriented modeling (OOM) software Dymola (2015 FD01) which uses the open-source code Modelica. This model includes car body flexibility with the assembling of a rigid body approach. The developed model is compared to a three-dimensional vehicle model in the commercial Vampire software (Pro V5.50) at different velocities. For the vertical ride comfort analysis, the ISO 2631-1 standard was used for both the developed model and the three-dimensional model. The results are presented as acceleration history and awrms—weighted r.m.s (root mean square) of accelerations—as required by the standard. The developed model has shown its feasibility in terms of its efficiency and accuracy for the vertical ride comfort analysis. The accuracy of the model is evidenced by the fact that the car body vibration level at high speeds shows minor differences compared to the results of the Vampire, which is a validated commercial software in the area of rail vehicle dynamics. The approach involving the assembly of rigid bodies is applied for the first time for high-speed trains in dynamical modelling, with flexible car bodies for ride comfort analysis. Furthermore, it can be used for parametrical studies focusing on ride comfort, thereby offering a quite beneficial framework for addressing the challenges of ride comfort analysis in high-speed rail vehicles. Improvements for and analyses of other aspects are also possible, since the optimization and other useful libraries are readily available in Dymola/Modelica.

Impacts of On-board Energy Storage Devices on the Energy Consumption of Train Operations

Urban rail transit systems consume significant electrical power, with traction accounting for 50% of the total energy (from China Urban Rail Transit Association [1]). As operational mileage and vehicle counts rise, so does energy consumption, underscoring the importance of vehicular energy conservation. This study evaluates the impact of on-board energy storage devices on train energy efficiency. Using operational data from Changsha Metro Line 5 and incorporating literature reviews and simulations, the energy-saving potential was assessed. Integrating these storage devices with vehicle energy monitoring systems shows promising potential for energy conservation and operational efficiency. This research presents a viable strategy to reduce energy consumption in urban rail vehicles, enhancing system competitiveness.

High potential: lightweight optimised structural design of car bodies for railway vehicles with alternative drive systems

Climate change and related goals and measures require a shift away from fossil fuels as an energy source. One solution for non-electrified lines for rail transport is the use of alternative drive technologies such as battery or hydrogen drive instead of diesel units. In order to use these efficiently in rail vehicles, it is imperative to make adjustments to the body structure. Existing car body structures must be adapted to integrate the space-intensive and heavy additional equipment components. Within the framework of the project AnoWaAS those with the highest lightweight construction potential are methodically identified from a large number of different derivatives of car body designs. The high influence of a force flow-compliant design on the lightweight potential is analysed in depth. Possible adapted construction methods for further exploitation of the lightweight potential are shown and analysed with regard to their potential. With the help of trapezoidal windows and the structural integration of equipment enclosures, it is possible to reduce the structural mass of a car body by more than 20%.

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.

Repeated impact response of honeycomb sandwich panels based on the failure parameters of adhesive layer and material

Honeycomb sandwich structure has been widely used in lightweight and impact protection of rail vehicle structures due to its excellent mechanical properties. In this paper, the plastic deformation, failure response and energy absorption characteristics of honeycomb sandwich panels for rail vehicles under repeated impact loads were studied. The three-point bending tests and low-speed impact tests of honeycomb sandwich panels were carried out, and a three-dimensional numerical model considering the detailed structure of the honeycomb core and the failure of the adhesive layer was established. The model can reasonably simulate honeycomb sandwich panels’ stiffness, strength, and structural failure. The effects of impact times and impact angle on the performance indexes of the honeycomb sandwich panel were studied. The results show that when the impact energy is the same, the impact times will affect the energy absorption distribution of honeycomb sandwich panels. With the increase in impact times, the panel’s absorption energy decreases, the core’s absorption energy increases, and the total absorption energy decreases. For multiple impact conditions, with the increase of impact times, the single energy absorption of the upper panel and core decreases, and the single energy absorption of the lower panel increases. When the impact energy is the same, the rise in impact angle will increase the damage to the honeycomb sandwich panel, and the energy absorption of each part will increase. In addition, the influence of impact times on the energy absorption efficiency of honeycomb sandwich panels is related to the impact angle.

Study on the crashworthiness of multi-cell thin-walled tubes filled with triply periodic minimal surface lattices

To improve energy absorption and efficiency and develop a structure with outstanding energy absorption capability, this study proposed designing multi-cell tubes filled with triply periodic minimal surface (TPMS) lattices. Based on experimental and simulation methods, the crashworthiness of multi-cell tubes filled with three types of TPMS lattices (Diamond, Gyroid, and Primitive) was investigated. Five multi-cell tube structures were fabricated by increasing the thin-walled tube corner units, improving the energy absorption efficiency by 67.98%. The results show that due to the coupling between TPMS lattices and thin-walled tubes, multi-cell tubes filled with TPMS lattices exhibited better crashworthiness performance. The energy absorption of multi-cell tubes filled with Diamond, Gyroid, and Primitive lattices increased sequentially. The energy absorption per unit mass and energy absorption capability were most notably enhanced for the multi-cell tubes filled with Diamond lattice, with energy absorption efficiency 17.24% higher and energy absorption 104.26% greater than empty multi-cell tubes. This inspires crash designs of rail vehicles and automotive fronts.

Innovative Materials Based on Epoxy Resin for Use as Seat Elements in Bulk Transport.

The subject of this research is the development of epoxy composites with a defined service life for the purpose of seat elements in rail vehicles, which will be more environmentally friendly. The produced materials based on epoxy resin filled with PLA or PLA and quercetin were subjected to solar aging tests for 800 h to investigate the impact of the additives used on the aging behavior of the epoxy matrix. Firstly, the TGA analysis showed that the use of the proposed additives allowed for the maintenance of the thermal stability of the epoxy resin. Moreover, based on an optical microscopy test, it was noticed that the introduction of PLA and PLA with quercetin did not contribute to an increase in matrix defects. The one-directional tensile tests carried out before and after solar aging showed that the presence of polylactide in epoxy composites causes a slight growth of the stiffness and strength. Based on contact angle and color change measurements, it was found that quercetin was oxidized, thus ensuring protection for the epoxy matrix. This phenomenon was confirmed by FTIR study, where the carbonyl index (CI) value for the R-PLA-Q composite was lower than for the reference sample. The obtained composite structures may be a good alternative to traditionally used systems as seat elements in rail vehicles, which are not only characterized by high aging resistance but are also more eco-friendly.

Model of energy consumption by brake discs of rail vehicles

The aim of the article is to present a computational model to determine the losses generated by the brake discs of rail vehicles. The energy consumption of the disc (energy losses) is divided into inertia losses and fan losses. The article is preceded by a review of the design solutions of brake discs of rail vehicles in terms of their ventilation and cooling after braking. Particular attention was paid to three types of brake disc designs with ventilation blades, bars and other shapes of ventilation bridges, and how the ventilation of these discs affects energy losses. On the one hand, forced ventilation of brake discs shortens the cooling time after intensive braking, on the other hand, it causes energy losses due to forced ventilation when the brakes are not used. The article presents the state of knowledge regarding the cooling efficiency of brake discs as a result of forced ventilation and presents a method for calculating the energy consumption generated by the brake disc in relation to the rotational speed. The energy losses were divided in the article into inertia losses due to the rotating mass and losses on the fan, in which the energy necessary for the rotation of the brake disc was determined from the method of calculating centrifugal fans with known geometric dimensions.

Accelerated degradation test method and performance prediction with service mileage of the yaw damper in railway vehicles

The performance of the yaw damper for rail vehicles degrades significantly degradation after long-term operation, which directly affects the dynamic behaviour of the vehicle operation. To quickly achieve the performance degradation of the yaw damper and predict the operating mileage under actual service conditions, the operating displacement spectrum of the yaw damper under actual operating conditions is analysed and decomposed using the short-time Fourier transform. Based on the equivalent principle of energy loss during vibration attenuation, an accelerated test method is proposed for the performance degradation of yaw dampers. By conducting the accelerated degradation test of the yaw damper on the test bench, the continuous degradation relationship between the performance parameters of the damper and the loading times is obtained. By combining the operating displacement spectrum and the accelerated degradation test data, the performance degradation trajectory model of the yaw damper is established, taking into account the equivalent energy loss between the service mileage and the loading times. The mapping relationship among loading times, service mileage and performance degradation is constructed. Finally, parameter performance tests are conducted on yaw dampers under different service mileage to verify the accuracy of the performance degradation trajectory model. The results show that the proposed acceleration test method and degradation trajectory model can quickly realise the performance degradation of the damper and accurately predict the performance parameters for different service mileage under actual operating conditions.

Dynamics modeling of urban rail vehicle axle-box bearings with roller defect considering time-varying impact

Accurately simulating the vibration response of the axle-box bearing with a localized defect on the roller can guide the proposal of several health condition estimation methods. However, there is still a lack of discussion and analysis on the detailed motion process of the roller defect passing through the inner/outer race. For filling this gap, a roller defect model considering time-varying impact is proposed and applied to the vehicle–track coupling system considering axle-box bearings. In addition to the Hertz contact force due to the relative displacement between the roller and race, time-varying impact excitation is designed according to the law of the conservation of energy. At first, an onsite test and an experimental test are implemented to validate the accuracy of the roller defect model and the vehicle–track coupling model, respectively. Then, the effect of the roller defect on the vibration characteristics of the components in the vehicle system is investigated. Finally, the influence of the defect size and vehicle speed on the vibration response of the axle-box bearing is studied, and the change rule of the time-varying impact is also researched with the defect size. Besides, the axle-box vibration response is simulated under variable vehicle speeds, and order tracking technique is applied to analyze the simulated result.

A critical review of wheel/rail high frequency vibration-induced vibration fatigue of railway bogie in China

PurposeThis review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.Design/methodology/approachVibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps.FindingsThe results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue.Originality/valueThe research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.

Vasúti közlekedés során keletkező zajok okainak és hatásainak elemzése

Noise emissions from rail transport are a major concern, as they affect both the environment and people's health and quality of life. Among the many sources of noise emissions, rail vehicles and infrastructure are a major factor. With regard to rail noise emissions, it can be concluded that noise effects are influenced by a number of factors. These factors include train speed, track condition, traction technology and the noise abatement methods used. The negative effects of noise exposure include sleep disturbance, stress and mental health deterioration. It also affects the quality of life of people in urban areas and property prices. It should be emphasised that reducing noise emissions from rail transport is key to creating a healthier and more sustainable urban environment. To achieve this, it is important to use modern noise abatement technologies, improve infrastructure and implement noise abatement actions effectively. Transport authorities and railway companies should work together to achieve a more noise-free rail transport, to improve people's quality of life and to protect the environment.

Fused deposition modelling of dense complex-shaped SiCp/Al composites with excellent properties

SiCp/Al composites are widely used in space vehicles, electronic packaging, automobiles, rail vehicles and other fields due to their excellent mechanical and thermal properties. Complex-shaped SiCp/Al parts are usually manufactured by mechanical processing, which is expensive and time-consuming due to the high hardness of SiC phase. As a highly effective 3D molding method, Fused Deposition Modelling (FDM) of the complex-structure SiCp/Al composites was reported for the first time in this paper. SiCp/Al composites was densified by pressureless infiltration after FDM, and as-acquired bulk possessed high densification of 92.67 % and the SiC volume fraction of 43.2 %. Moreover, excellent performances were also presented, including flexural strength of 211 MPa, thermal conductivity of 112(W/m·K), and the thermal expansion coefficient of 8.67 × 10-6K−1.

Experimentally Determined Force Density Spectra for Admittance-Based Vibration Predictions along Railways

The planning application and approval process of railway tracks is generally accompanied by a vibration immission assessment. Starting with the source spectrum, which is ideally obtained through measurements, the German guideline VDI 3837 recommends a series of multiplications using transfer spectra which account for the various subdomains of the wave propagation path, such as the effect of the superstructure, the free field propagation, the soil-structure coupling and the transmission inside buildings. Typically, these one-third octave spectra are an average over empirical reference values. While simplified empirical relations are prone to a large variance, the use of artificial vibration sources allows the actual vibration transmission behavior from the tracks to the immission points to be quantified. Using so-called transfer admittances, also known as transfer mobilities, which account for all dynamic interactions along the transmission path (track, tunnel structures, foundations, structural properties), together with force density spectra for relevant rail vehicles, the authors investigate the practical application of the method presented in Report No. 0123 of the Federal Transit Administration (2018) for the frequency range 5–200 Hz. The article demonstrates how such force density spectra were obtained for the most common train types in the Austrian rail network at two different track sections using artificial vibration sources. Furthermore, practical aspects are discussed and a recently developed approximation method for estimating line transfer admittances from point transfer admittances using simplified models is introduced.

The Safety, Operation, and Energy Efficiency of Rail Vehicles—A Case Study for Poland

The objective of the article was to describe the importance of a good technically and economically planned process for purchasing a rail vehicle. Compliance with this process with safety standards and energy efficiency is crucial regarding effectiveness in the long-life cycle cost of a rail vehicle. Methods that were used focused on audit and document analysis. In the result based on a specific audit of a railway company, some non-compliances were found, and it was methodically proven that they are significant risk factors in terms of performing such processes in the future. Major conclusions regarded the importance of fulfilling legal requirements of SMS for purchase purposes, involvement of a safety engineer post in this process, and usage of technical feedback regarding previous operation of railway vehicles and operational findings from the past. The transport policy of the EU and other developed countries sets ambitious goals for reducing energy consumption in transportation activities, which is linked to the aim of reducing environmental burdens.

Acceleration-based friction coefficient estimation of a rail vehicle using feedforward NN: validation with track measurements

Low friction can lead to poor adhesion conditions between the rail and wheel, which is detrimental to rail vehicle operation and safety. Up to date knowledge of the rail-wheel friction level is currently not available across rail networks, meaning planning mitigation strategies is difficult. This paper presents a real-time friction coefficient estimation algorithm based on a feed-forward neural network (FNN). Unlike conventional methods, the FNN does not depend on slip/adhesion curves or creep force models, and only requires wheelset longitudinal acceleration and speed. The wheelset acceleration and friction measurements are obtained by running a two-car rail vehicle on a friction-modified track with five different levels of friction conditions at four different vehicle speeds. Four different FNNs are trained for four speed conditions, and their estimation performance were validated by training multiple FNNs and testing them in each speed case using new sets of data. Validation results show that the average mean absolute errors from the four FNNs remains below 0.0083.

Determination of the resistance to motion of a cargo train when driving without a drive

The issue related to the motion resistance of a rail vehicle is very important for energy, environmental and related energy consumption of the vehicle as well as vehicle performance with dynamic points. The latter aspect applies in particular to traction vehicles. The article presents several models of resistance to movement of a freight train used by various railway authorities, for Polish and foreign rolling stock. The resistance values obtained from the models were verified against the tested freight train carrying aggregate. On the basis of the records from the locomotive recorder, linear models of speed changes over time and coasting paths (without drive) were determined. On the basis of the values obtained from the models of resistance to movement of a freight train, the paths of coasting to stop the train were determined on the basis of the UIC 544-1 card, which were related to the analyzed freight train.

When contract clauses conflict: The Salvador light rail vehicle concession

Infrastructure concession contracts may include clauses that allow for capacity expansion, term extensions, or even risk management strategies such as cap and floor schemes. These clauses provide project managers with the flexibility required to adapt their operational strategies as new information is revealed in time and limit investor risk. However, when contracts include combinations of these clauses, determining their overall impact on the objectives of the contract and the project is non-trivial and require the combined analysis of these effects. While the literature on the valuation of infrastructure projects tends to focus on a single type of flexibility at a time, we analyze the combined interaction between these clauses and their impact on the overall value of the project under the real options approach. Using the Salvador Light Rail Vehicle (LRV) concession project as a numerical example, our results suggest that these clause interactions can have non-intuitive results and negatively affect the stated objectives of both parties in the contract. We also show how policy makers can use this information to improve the value of the project to society and reduce the risk to the government.

Development and Testing of a UWB-Based Vehicle-to-Vehicle (V2V) Ranging System for Self-Propelled Rail Vehicles

Development and Testing of a UWB-Based Vehicle-to-Vehicle (V2V) Ranging System for Self-Propelled Rail Vehicles