Thermal track buckling is probably the major problem due to the advent of continuous welded rail track. In fact, when the rails temperature rises over a critical value, the track can buckle, suddenly or progressively, in the lateral plane. Both poor ballast conditions and large lateral alignment defects are the principal causes of such phenomenon. In a previous paper, a parametric finite element model for thermal track buckling simulation was presented and validated by comparison with analytical results of the literature. In this study, the finite element model has been further validated by comparison with analytical and numerical results obtained by three other authors. Moreover, to take into account the effect on the buckling temperatures of the vertical loads due to train passes, the tie-ballast lateral resistance has been modified along the track, taking into account the vertical reaction forces distribution induced by axle loads. A sensitivity analysis has been carried out both for tangent and curved track, considering two values of the alignment defect amplitude, and different values of the parameters that characterize actual railway vehicles. It is found that the conditions to trigger progressive buckling (△ T max ≈ △ T min ) are attained with small values of the truck center distance, and in a more accentuated manner in the presence of high values of the lateral alignment defect. △ T max and △ T min increase with axle spacing, and this increase is more pronounced for low values of the truck center spacing. △ T max and △ T min also increase with curve radius, but decrease for increasing values of the misalignment defect amplitude. In explosive buckling conditions (△ T max ≠ △ T min ), there is a limit value of the truck center distance above which the vertical load has no more effects, and the results of the static thermal buckling are found.

Laser welding has received increased interest in the rail industry due to its outstanding performance in aesthetics, strength, heat affected area, precise control and sealing. This paper introduces the laser-welded stainless steel carbody used in subway cars. The carbody structure, welding methods, strength and fatigue analysis methods, and test verification and validation results are discussed. Firstly, the shear strength of laser welding on stainless steel with different thickness combinations were obtained through tests. The preliminary carbody structure was designed based on the material and welding properties. Then the finite element analysis (FEA) was conducted on the preliminary design to evaluate the strength and optimize the structure. After the optimization was completed, a full-size car was manufactured, and the strength test was performed. In the process of FEA and strength evaluation, the simulation accuracy of different element types and the influence of loading force directions have been considered. Based on the design, simulation and test data, a complete laser welding carbody strength evaluation system was established, which can provide valuable reference for researchers and engineers in the rail vehicle industry. The entire design, analysis and testing process complies with ASME-RT2-2014 and this is also one of the first to implement this standard.

With the development of high-speed rail technology, the interaction between wheel and track becomes more serious, which threatens the running stability, riding quality and safety of the vehicle. Due to the selected stiffness and damping parameters, conventional passive suspensions cannot fit in with the diverse conditions of the railway. Additionally, among these vibrations contains a large amount of energy, if this vibrational energy can be recycled and used for the active suspension to control, it will be a good solution compared to the conventional passive suspensions. Many energy-harvesting shock absorbers have been proposed in recent years, the most popular design is the electromagnetic harvester including linear electromagnetic shock absorbers, rotational electromagnetic shock absorbers, the mechanical motion rectifier (MMR), and the hydraulic electromagnetic energy-regenerative shock absorber (HESA). With different energy converting mechanisms, the complicated effects of the inertia and nonlinear damping behaviors will severely impact the vehicle dynamic performance such as the ride comfort and road handling. In the past few years, engineers and researchers have done relevant researches on HESA which have shown that it has good effects and proposed several suspension energy regeneration solutions for applying to car. This paper presents a novel application of HESA into a bogie system for railway vehicles comparing to the conventional suspension systems. HESA is composed of hydraulic cylinder, check valves, accumulators, hydraulic motor, generator, pipelines and so on. In HESA, the high-pressure oil which is produced by shock absorber reciprocation could be exported to drive the hydraulic motor, so as to drive the generator to generate electricity. In this way, HESA regenerate the mechanical vibrational energy that is otherwise dissipated by the traditional shock absorber as heat energy. Because the bogie has two sets of suspension systems, a dynamic model of bogie based on AMESim is established in order to clarify the influence of the dynamic characteristics effect and the energy harvesting efficiency when installing the HESA into different sets of the bogie. Then, set the HESA model into each suspension system of the bogie and input with the corresponding characteristic excitation, the influence of the dynamic characteristics and the energy harvesting efficiency are analyzed and compared. The simulation results show that the system can effectively reduce the vibration of the carriage, while maintaining good potential to recycle vibratory energy. Based on the results of the simulation, the relationships as well as differences between the first suspension system and second suspension system have been concluded, which are useful for the design of HESA-Bogie. Moreover, comparing the energy harvesting efficiency discrepancy between the two suspension systems, the potential of energy harvesting of a novel railway vehicle bogie system with HESA has been evaluated and then the best application department has been found, which indicates the theoretical feasibilities of the HESA-bogie to improve the fuel economy.

Advanced active suspension systems has attracted considerable attention in modern railway vehicle designs in recent years. The purpose of the suspension is to attenuate the vehicle vibrations due to various rail excitations. With active suspensions it is aimed to improve the performance in some cases, while not making it worse in others. The performance-related objectives can be approximately translated in different norm bounds on certain transfer functions or impulse responses. In this paper, a multi-objective problem is formulated as a non-convex and non-smooth optimization problem for a full-car railway vehicle modelled with seventeen-degrees-of-freedom (17 DOF) and excited by random rail inputs. The controller order restricted to be less than or equal to the passive system model order. For a range of orders, controllers are synthesized by using the HIFOO toolbox.

When a mechanical component of a railway vehicle experiences failure due to fatigue, it is necessary to determine whether it has been an isolated failure or it is a systematic failure that may affect the whole fleet. The present work presents the methodology to be followed for the application of on-track tests to determine the probability of fatigue failure. By simulating a normal commercial service in one or multiple conditions, the stress levels experienced by the component are recorded. These stress levels are combined and extrapolated in order to determine the typical global stress history that the component will experience during its operational life. From this stress history, the risk of fatigue failure can be estimated by means of the cumulative damage method also known as Miner’s rule. For this calculation the measured stress levels have to be compared with an S-N curve. The problem arises because the S-N curves presented in the standards correspond to stresses in the direction perpendicular or longitudinal to the weld. The peculiarities of on-track tests imply that the direction of principal stress may vary continuously and the maximum stress value may be present in specific points of the record with directions that do not represent the normal behaviour of the piece. Different forms of dealing with the projection of the rosettes have been analyzed, and the influence of these considerations on the damage calculation has been studied.

The application of Operational Modal Analysis (OMA) in the railway sector opens a broad field of opportunities. The validation of the numerical model employed in the design phase is usually performed employing data obtained in static tests. The drawback is that some suspension parameters, such as dampers, only have an influence in the dynamic behavior and not in the static behavior. Because of that, the use of the mode shapes identified from track measurements in combination with the static tests leads to a more accurate validation of the numerical model. Apart from that, most passenger comfort and dynamic problems are associated to slightly damped modes. A correct identification of the modal parameters can be used as a continuous design improvement tool to improve the comfort and dynamic characteristics of future designs. Another valuable application of OMA techniques is the identification of the mode shapes corresponding to instabilities, due to the safety impact that they have. In railway vehicles, instabilities are associated to mode shapes that present a damping rate which decreases with the increase of the running speed. Above a certain speed value, the excitation coming from track cannot be damped by the vehicle and it reaches an unstable condition. This unstable condition leads to high acceleration levels experienced by the passengers and high interaction forces between the wheel and the rail that may lead to safety hazards. The speed above which the vehicle is unstable is known as critical speed, and has to be greater than the maximum speed of the vehicle with a reasonable safety margin. The use of OMA techniques allows identifying the mode shape that causes the instability. This paper presents the application of OMA techniques to measurements performed on a passenger vehicle, in which the speed was increased until the vehicle was unstable. The mode shape that caused the instability was identified as well as its corresponding natural frequency and damping rate.

This paper discusses the development of a state of the art single-wheel roller rig for studying contact mechanics and dynamics in railroad applications. The use of indoor-based simulation tools has become a mainstay in vehicle testing for the automotive and railroad industries. In contrast to field-testing, roller rigs offer a controlled laboratory environment that can provide a successful path for obtaining data on the mechanics and dynamics of railway systems for a variety of operating conditions. The idea to develop a laboratory test rig started from the observation that there is a need for better-developed testing fixtures capable of accurately explaining the relatively unknown physics of the wheel-rail contact mechanics and dynamics. Developing a better understanding of such physics would assist with designing faster, safer, and more efficient railroad systems. A review of the existing roller rigs indicated that many desired functional requirements for studying contact mechanics are not readily available. The Virginia Tech Railway Technologies Laboratory (RTL) has embarked on a mission to develop a state-of-the-art testing facility that will allow experimental testing for contact mechanics in a dynamic, controlled, and consistent manner. The VT roller rig is intended to allow for actively controlling all the wheel-rail interface degrees of freedom: cant angle, angle of attack, and lateral displacement. Two AC synchronous servomotors, accompanied with proper gearheads, accurately drive the rotating wheels. A novel force measurement system, suitable for steel on steel contact, is configured to precisely measure the contact forces and torques. The control architecture is developed based on the SynqNet data acquisition system offered by Kollmorgen, the drive-motor and actuator supplier. The Synqnet provides a unified communication protocol between actuators, drives, and data acquisition system; therefore eliminating any difficulty with data conversion among these units. Other auxiliary sensors and measurement systems are implemented to help with characterizing the contact mechanics and contact geometry. This paper will describe the main steps in the design process of the VT roller rig and the final design solution selected. It will also present the testing capabilities of the rig. The design analysis indicates that the rig can successfully meet the set requirements: additional accuracy in measurements, and better control on the design of experiments.

This study uses a nonlinear multibody dynamics model of a railway vehicle with three-piece trucks to perform a parametric study on a wide range of parameters influencing the performance of the truck on tangent track. One of the major disadvantages of the three-piece truck is that its performance can be greatly influenced due to worn parts or contaminants on friction surfaces, such as the friction wedge. The influence of worn parts is modeled as increased gap between bodies, using dead-band springs. The influence of environmental contamination is modeled as change in coefficients of friction. Lateral accelerations, measured at the center of gravity of the leading axle of the leading truck (Axle 1) are used for the hunting performance of the vehicle. For the baseline case, an eigenvalue analysis of a linearized model is used to evaluate the effect of speed on damping ratio and lateral motion frequency. A comparison of the linear model and non-linear time series analysis show that the linear model is less conservative, in that it predicts that the onset of hunting occurs at higher speeds. The results indicate a direct relationship between various coefficients of friction and hunting velocity of the rail vehicle. Increasing the gap between the pedestal legs and bearing housing does not influence hunting velocity, but reduces lateral acceleration magnitudes during hunting. The weights of the carbody and cargo also has a direct relationships with hunting velocity, meaning that hunting occurs at lower speeds for unloaded car and at higher speeds for a loaded car.

This paper provides a detailed dynamic model of the electromechanical system for a scaled roller rig that is under construction at the Railway Technology Laboratory of Virginia Tech (RTL) for accurate study of the mechanics and dynamics at wheel-rail interface in railway vehicles. Roller rigs are critical laboratory test equipment for studying rail vehicle dynamics, either as a full railcar or single component. The controlled laboratory environment will provide a successful path for obtaining data on the mechanics and dynamics of the system, including creepage and creep forces at the wheel-rail interface under various conditions. The single-wheel scaled rig under development at RTL includes a wheel that is placed on a roller with similar profile as a U.S. 136 weight rail. The test setup allows for adjusting the wheel load, the wheel angle of attack, the rail cant, and the lateral position of the wheel with respect to the rail (including flanging). The roller and the wheel are each powered independently by two AC motors that enable controlling their relative speed to a high degree of precision, i.e., 0.1 RPM, in order for precisely controlling and simulating various creep conditions that occur in practice. An essential step for the successful design and development of the test rig is modeling the motors and the roller/wheel drivelines. The model includes the electromagnetic dynamics of the AC motors, the compliances and damping of the drivelines, the inertial properties of the motors, shafts, couplers, and the rotating wheels, in a multi-domain (electrical, magnetic, and mechanical) lumped-parameter model. The model is used to determine the damped natural frequencies of the coupled system. The results of the study indicate that the compliances of the driveline mechanics is the most critical element in maintaining a prescribed speed at the driven wheel, and also controlling the relative creep between the wheel and the simulated (round) rail.

Nowadays the application of experimental modal analysis techniques on railway vehicles is gaining importance. A correct identification of modal characteristics allows improving the dynamic behavior design of the vehicle and so reaching higher running speeds and accomplishing better comfort levels. So far, in the railway sector only conventional modal analysis techniques have been used. With these techniques, the modal parameters are determined during a static test by measuring the responses of the system to one or multiple known forces. This paper presents the application of the Operational Modal Analysis (OMA) technique on a railway vehicle. This technique determines the modal parameters employing only the responses of the system to an unknown excitation. In this way, the data to be used can be acquired during on track test which presents three main advantages. The first one is that the nonlinear components of the suspensions are working in their normal operating condition which is difficult to achieve during a static test. The second one is that the wheel spinning effect is taken into account. Finally, the test can be combined with other type of track tests, reducing the period of time before delivery of the vehicle to the client. In the case under study, the OMA technique is applied by means of commercial software to measurements performed on a passengers train. The modal parameters obtained for the carbody and one of the bogies are presented.

In the past 25 years, laws related to accessibility in general have been enacted worldwide. In the United Kingdom, for example, with the passing of the Disability Discrimination Act (DDA) of 1995 and 2005, a number of regulations and codes of practice have been put in place to provide wheelchair users with greater access and freedom of traveling by public transport, including railway vehicles. This paper aims at contributing to the knowledge gap that exists on how human related factors may influence the safety of a wheelchair occupant in a railway vehicle during deceleration, particularly crash conditions. To achieve this, a socio-technical study on railway vehicle safety was conducted through a disability association called BADGE, acting as the gatekeeper. The research methodology developed applied two data collection research tools. The first was a focus group discussion in which six wheelchair users participated. The second tool was observational, where wheelchair users undertook two baseline railway vehicle trips within the Greater Manchester. Here data was captured through video footage and still pictures. In addition, note taking was applied. The research found that personal preferences and medical conditions greatly influence the way a wheelchair occupant interacts with the wheelchair and the railway vehicle. This could potentially affect the safety of the wheelchair occupant, generally, and particularly during a crash. The paper ends by presenting a flow diagram that postulates how these human related factors identified could ultimately influence secondary collision characteristics during a crash. The findings could help railway vehicle engineers to better design wheelchair accessible environment with improved wheelchair occupant crash safety.

This paper investigates the relationship between end hose elasticity and the potential amount of energy coupled railroad cars can absorb in charged condition before pull a part force separation occurs. One of the most significant issues with the existing end hose is that it will uncouple after enough force is applied causing a loss of pressure in the brake system. Our initiative to evolve the end hose into a more durable wire braided rubber material from the standard hand wrapped construction has decreased this potential for separation in the field. Simulation testing using end hoses from three manufacturers is studied and compared. Charged hose assemblies were coupled and pulled apart. The results showed one end hose stretched nearly double the distance of the other hoses. Analysis of the resulting data will show that a more elastic hose will allow a train brake system to absorb more energy thus reducing the opportunity for a disconnect while in service.

KRRI (Korea Railroad Research Institute) has successfully performed several tens of impact tests of crash parts for a railway vehicles. Full-scale crash testing facilities were newly established including a crash barrier, dynamic load cell, high speed DAS (Data Acquisition System), a laser displacement sensor, dummies, a motor car and etc. This paper introduces series of impact test results using full-scale crash testing facilities. The impact test for railway vehicles consists of three categories, i.e. single item tests, module tests and crash structure tests. For single item tests, expansion tubes, composite tubes, collapsible tubes and etc. were tested. For module tests, a crash test of a light collision safety device with an expansion tube and triggering mechanism was performed. For crash structure tests, several full-scale crash tests were performed including front-end and cab structures with or without dummies. The crash testing equipment developed will be able to evaluate the occupant safety as well as the structural crashworthiness of a train.

The more demanding safety and comfort requirements combined with the increasing maximum speed of trains have lead to a growing concern in aspects such as the determination of the modal parameters of railway vehicles. Until now, the modal parameters of a vehicle have been obtained by EMA (Experimental Modal Analysis) based on the application of an impact force on the vehicle frame. However this kind of test is not optimal for railway vehicles because, due to their large dimensions, an impact force is unable to excite all the points of the structure. Also, with this method only the structural modes can be analyzed. Because of these drawbacks, a new modal analysis methodology is proposed, in which the excitation force comes from a specially designed shaker mounted under a point of a test track. In this manner, real excitation conditions can be simulated and it allows to determine not only the structural modes, but also the vibration modes associated with the suspensions. In first place, a description of the test facilities is presented. Afterwards, we present a test carried out in one of the coaches of a high speed train. The instrumentation employed, test methodology and test results are described. Finally, the test results are compared with the results obtained from a modal test in which impact excitation was used. Also the vibration modes obtained in the test are compared with the theoretical ones, which have been calculated with a combination of a FEM (Finite Element Method) and a MBS (Multi-Body Simulation).

Embankment is a typical layout for rail infrastructures and train aerodynamic coefficients in this scenario are necessary for the analysis of cross wind effects. Nevertheless wind tunnel tests on scale models with the embankment scenario presents difficulties in the reproduction of the boundary conditions, that is the simulation of a “pseudo-infinite” full scale embankment. To investigate this topic we have performed wind tunnel tests on an ETR500 1:45 scale model using a finite length embankment, with and without an upwind nose and a “pseudo-infinite” embankment, reproduced by the extension wall-to-wall of the scenario. The paper presents the tests results in terms of aerodynamic force coefficients and surface pressures. Guidelines for wind tunnel tests on embankment are than discussed.

In recent years, image recognition, along with improvements in image processing technology, has become a mainstream method of object inspection. The quality of images directly affects the image-recognition rate. Track monitoring systems play an important role in ensuring safety and preventing derailments of trains, on the basis of the prevailing track conditions. Therefore, the conditions of track systems are very important. In this research, a high-speed frame grabber system is designed. The triggering rate of its line scan camera can be adjusted to match the vehicle speed of the train, so that the pixels per inch of images captured by this camera are fixed. The hardware equipment of the designed system includes a line scan camera, an image acquisition card, artificial lightings, a contrast sensor, and a system on a programmable chip (SOPC) development board. An exposure time control system is designed on the basis of a field-programmable gate array (FPGA) core. The designed system can acquire clear high-speed images while the vehicle speed changes dramatically. The experimental results confirm the feasibility of using line scan cameras for railway vehicles.

This study aims to create a numerical analysis model which can investigate the interaction between pantograph and overhead contact line used for railway vehicles, and validate the simulation results according to EN 50318 standards. Finite element analysis models of pantograph and overhead contact line are created using SAMCEF, a commercial FE analysis program, and mean, standard deviation, maximum and minimum values of contact forces are obtained. The simulation results are validated according to EN 50318, and the reliability of SAMCEF as an analysis solver of railway vehicle’s catenary system is discussed.

In the last 7 significant accidents on the railways in GB there have been 60 passenger fatalities. 14 of these have been caused by ejection (passengers being thrown from the train during the course of the collision). One additional fatality was attributed to an object entering the carriage through the train window. In total there have been 26 ejections with over 50% resulting in fatality. The trend has been towards higher speed incidents involving vehicles overturning. The authority responsible for setting Safety Standards and, conducting research on behalf of the Train Operators and Stakeholders in GB’s railways is the Rail Safety and Standards Board (RSSB). They initiated a multi faceted stream of research to investigate the performance of glazed systems in train incidents. The aim of the research was to identify and establish measures which replicate the conditions to which glazed systems may be subject to in collision conditions and to formulate corresponding performance requirements designed to prevent passenger ejection. The research was phased and entailed the following: • Accident investigation and analysis, detailed vehicle examination. • Review of 600 passenger witness statements, obtained by British Transport Police. • Generation of computer models using the MADYMO code and Side Impact Dummy (SID) to model the overturning event in a variety of conditions. • Postulation of events and measures based on analysis. • Proposed test programme. • Construction of new test apparatus. • Construction of existing glazed units — benchmarking process. • Construction of glazed units of improved design utilising different glass specifications and laminations but capable of being fitted into existing frames. • Testing, reporting, stakeholder reviews and the production of a new equipment standard for glass in railway vehicles. The research team was keen to include a glazing company capable of providing the highest level of technical support. Independent Glass, a Scottish company had been making significant strides in improving the penetration performance of glazed units (especially at the extremes of ambient temperature conditions) was chosen to produce glass samples for the project. A significant amount of testing was undertaken at their premises in Glasgow. Additionally the new tests were undertaken which demonstrate improved penetration resistance by heavy objects and improved passenger containment. This research has been embedded in the proposed new RSSB standard “GM/RT 2100” [1] which has developed a new scenario based sequential testing regime for glazed laminated systems in railway vehicles. This paper will inform the audience of these new requirements and the research which led to its introduction. It will show the testing that has been undertaken from the perspective of the glazing manufacturer and will detail the equipment that is required to be able to perform these new tests. It will comment on the cost and mass implications of fitting these new glazing units to vehicles in GB and the safety benefit of doing so. Toughened windows are still being used by some train operators for emergency egress; however most operators are now converting their vehicles to having entirely laminated units in vehicles. This is not the subject of this paper.

As track geometry degrades, and in particular as track surface and cross-level (as defined by a Track Quality Index or TQI) degrades, railway vehicles going over that degraded track experience increased vertical dynamic behavior and increased vehicle/track interaction. This in turn translates into increased wheel/rail dynamic forces as well as increased energy (fuel) consumption. While this concept has been known for many years, there has been limited study of the direct relationships between the degree of track degradation (as quantified by a Track Quality Index type parameter) and the magnitude of the dynamic force and energy consumption increase. This paper presents a recent study on the dynamic effects of track surface geometry degradation, which has direct impact on maintenance practices, policies, and economics. Specifically, this paper presents the results of a series of analyses looking at the effect of increased track geometry degradation, as measured by a track geometry inspection vehicle, and quantified by a Track Quality Index (TQI). The effects examined include loss of energy and wasted fuel due to dissipation of energy in the vehicle suspension, as well as the increase in dynamic vertical force at the wheel/rail interface. The analyses used over 100 miles of US main line (Class 1) railroad track geometry data for a broad range of track conditions (and corresponding Track and Surface Quality Indices); together with a sophisticated multi-degree of freedom vehicle dynamics model to develop a relationship between track condition and dynamic effects. The results are a series of non-linear relationships between track condition, as defined by TQI, and energy loss in the suspension system, i.e. energy dissipation. A second set of non-linear relations was also developed between track condition, as defined by TQI, and dynamic force multiplier, i.e. the ratio of dynamic force to static wheel/rail load. The paper presents these results in both mathematical and graphical form.

A target-oriented method for the design of railway wheel profiles is presented. The target chosen is the rolling radii difference function which plays an important role in the dynamics of railway vehicles especially for high speed performances. A computer program based on this method has also been developed and is validated by way of examples in which wheel profiles LMA, S1002G and XP55 are investigated.