Railway Vehicle Derailment Research Articles

A parametric approach for enhancing the accuracy of instrumented wheelset: A case study

The instrumented wheelset (IWS) is the most commonly used wheel–rail force test method, playing a crucial role in assessing the risk of derailment of railway vehicles. To enhance the accuracy of IWS, the study first investigates error sources and addresses the importance of eliminating the errors caused by contact point shift and wheel rotation. Functions related to the angular and radial position of strain gauges, the wheel–rail force amplitude and the wheel profile have been obtained. Parametric models for IWS error estimation have been established and used to transform the problem into an objective optimization problem. Validation through a case study using Particle Swarm Optimization with nonlinear constraints has confirmed the model’s convergence and stability. Comparative analysis, alongside stationary test, demonstrated a significant reduction in crosstalk and ripple errors, verifying the method’s effectiveness in enhancing the accuracy of wheel–rail force measurement.

Investigation on the mechanism and measures of derailment of empty freight train passing a turnout in the diverging route

The derailment of railway vehicles at a turnout is a worldwide concern. However, the derailment of empty freight trains in the switch section of a turnout in the diverging route is rarely concerned. Therefore, in order to analyse the derailment mechanism of empty freight trains in the turnout switch area and to propose appropriate preventive measures, field investigation and dynamic simulation of the derailment are carried out on the basis of an empty freight train derailment in the turnout switch area of the diverging route. Firstly, the background of the derailment is presented and the potential influencing factors of the derailment are analysed according to the field investigation. Secondly, a detailed train-turnout dynamic model is established, taking into account the variable cross-sections of the turnout switch rail and the effect of the longitudinal coupler force. Thirdly, based on the model, the derailment mechanism of the empty freight train is revealed through theoretical analysis and simulation calculation. Finally, the effect of the potential derailment influencing factors is analysed and preventive measures are proposed to reduce the derailment risk of the empty freight train at the turnout switch area in the diverging route. The results indicate that this derailment is caused by the combined effect of the inherent structural characteristics of the switch, the large longitudinal coupler force, and the high wheel rail friction coefficient. The possibility of derailment can be reduced by reducing the longitudinal coupler force and the wheel rail friction coefficient. In addition, the installation of a guard rail in front of the turnout can effectively prevent empty freight train derailment in the turnout area.

State-of-the-Art Wayside Condition Monitoring Systems for Railway Wheels: A Comprehensive Review

In recent decades, there has been a constant demand for faster, longer, and safer railway networks. This also brings challenges for condition monitoring systems in modern railway vehicles. More specifically, critical parts of railway vehicles like wheels degrade over time due to various operational and environmental reasons. Different dynamic effects such as skidding/sliding over the track and the presence of contamination between wheel-rail cause various wheel defects. Faulty wheels ultimately lead to the derailment of railway vehicles. To avoid worst situations like railway derailments, various research has been conducted for developing efficient condition monitoring systems for railway wheels. In addition, there have been some commercial condition monitoring products that can be deployed with railway vehicles. These systems incorporate various sensors such as strain gauges and vision sensors to collect data for diagnosis and prognosis. Various methods have been explored but yet there is a broad research gap in terms of developing advanced onboard condition monitoring systems. With the progress in technology, advanced systems with Machine Learning/Deep Learning methods can provide more efficient and robust condition monitoring of dynamic railway systems. Considering the need for advancement in condition monitoring systems for railway vehicles, a comprehensive review of existing condition monitoring systems for railway wheels is conducted in this paper. The review is aimed at understanding the feasibility and potential of new methods for modern railways. This paper provides a detailed overview of studies on the existing wayside systems and reports their advantages and disadvantages concerning its recently emerging counterpart on-board monitoring systems. Data acquisition systems and analysis methods are critically reviewed which could assist in developing more efficient and reliable condition monitoring systems for railway wheels. This article also reviews the current progress of wayside systems and their limitations. The article is targeted at the researchers and engineers working in this domain, who can pave the way for developing advanced and cost-effective condition monitoring systems for railway wheels using modern technologies.

Study on the derailment of the remote locomotive in a heavy-haul train with distributed power at the turnout frog area: field investigation and numerical simulation

The derailment of railway vehicles in the turnout area is a worldwide concerned issue. Previous studies mainly concentrate on the derailment at the switch area, and the risk at the frog area is seldom concerned. Based on a specific derailment case of the remote locomotive in a 20,000-tonne heavy-haul train, a study on the derailment of the locomotive at the turnout frog area is presented. The conditions of the derailed locomotive and turnout track are introduced, and the potential influence factors are screened according to the field investigation results. A detailed simulation model that considers the complex wheel-frog/guard rail contact relationship and the interaction between adjacent vehicles is established. Through numerical simulation, the derailment process of the locomotive at the turnout frog area is reproduced, and the derailment mechanism is revealed, followed by the influence analysis of the potential factors. The results indicate that the combined effect of the compressive coupler force and the coupler jack-knifing promotes the derailment remarkably. Moreover, the derailment at the turnout frog area is more likely to occur under low-speed conditions, and the possibility of derailment can be reduced by decreasing the compressive coupler force and the friction coefficients between the wheel and stock/frog/guard rail.

Hypothesis for fault dynamic monitoring evolution in railway systems

This paper presents the technical analysis and results of an inquiry carried out by General Directorate for Railway and Maritime Investigations (DiGIFeMa) belonging to Infrastructure and Transportation Italian Minister. The target of this study tries drawing how the prognostic theory can be applied to railway maintenance in order to optimize procedures and operational features on railway safety. The case of study points on a HS railway vehicle derailment event, that has analysed in an Official Investigation Report drawn by Italian Transportation and Infrastructure Ministry. This document, drafted according to Legislative Decree n. 50/2019, represents the identification of technical faults, which have generated the accident, and leads to specific technical recommendations. Starting from these results, one of the most important Italian Railway Undertaking has carried out a verification of the existing vehicle safety monitoring devices, used during high-speed rail operation. Moreover, due to the prognostic’s theory, a wide research and series of experimental tests could be developed on old and new devices which verify the functional status of mechanical elements connected to the rotation of the railway wheelsets.

Dynamic analysis of railway vehicle derailment mechanism in train-to-train collision accidents

Train collision-induced derailment may result in serious casualties. This study investigates the railway vehicle derailment behaviour and explores the derailment causes in train-to-train impacts. A train-track coupled dynamic model is developed and validated. The lateral ( Yde) and vertical ( Zde) relative displacements of the wheel/rail pair are used for the derailment evaluation. The results show that the wheelset jumping derailment and the saw-tooth buckling mode may occur during the high-speed collisions. Derailment is mainly caused by car body yawing rotation and wheelset lateral and vertical displacements. Yawing and pitching motions of car body influence wheelset displacement significantly. Vehicles with the higher velocity generate more severe derailment behaviour. Under circumstance of the same train impact energy, the higher vehicle mass and greater car numbers have the stabilizing influence for reducing the derailment risk. Increasing the force on the main energy-absorbing structure which is set in the front-end crushing zone of a vehicle to dissipate the train impact energy and the damping coefficient of the secondary yaw damper can decrease the derailment risk. The train safety operation areas and derailment boundaries indicate that the reliability of the Yde criterion is higher.

An investigation of rocking derailment of railway vehicles under the earthquake excitation

The rocking derailment mechanism of railway vehicles due to the earthquake-induced roll motion is investigated through a coupled vehicle/track dynamic model together with a simplified roll-plane vehicle model. The coupled vehicle/track dynamic model is formulated through a typical high-speed train model incorporating with a track model to study dynamic responses and rocking derailment procedure under earthquake excitations. The results indicate that the lateral earthquake excitation can impose significant effects on the running safety of vehicle, and further lead to the rocking derailment. A simplified roll plane vehicle model subjected to the lateral earthquake excitation is thus developed to derive the critical condition of rocking derailment, which further contribute to a criterion for earthquake- induced rocking derailment. Moreover, a conservative limit, in term of equivalent acceleration of lateral earthquake excitation, has been identified considering different earthquake excitations. This could serve as a threshold for assessment of operational safety of rail vehicle in the presence of earthquake condition.

Development of method for experimental determination of wheel–rail contact forces and contact point position by using instrumented wheelset

This paper presents the development of a unique method for experimental determination of wheel–rail contact forces and contact point position by using the instrumented wheelset (IWS). Solutions of key problems in the development of IWS are proposed, such as the determination of optimal locations, layout, number and way of connecting strain gauges as well as the development of an inverse identification algorithm (IIA). The base for the solution of these problems is the wheel model and results of FEM calculations, while IIA is based on the method of blind source separation using independent component analysis. In the first phase, the developed method was tested on a wheel model and a high accuracy was obtained (deviations of parameters obtained with IIA and really applied parameters in the model are less than 2%). In the second phase, experimental tests on the real object or IWS were carried out. The signal-to-noise ratio was identified as the main influential parameter on the measurement accuracy. Тhе obtained results have shown that the developed method enables measurement of vertical and lateral wheel–rail contact forces Q and Y and their ratio Y/Q with estimated errors of less than 10%, while the estimated measurement error of contact point position is less than 15%. At flange contact and higher values of ratio Y/Q or Y force, the measurement errors are reduced, which is extremely important for the reliability and quality of experimental tests of safety against derailment of railway vehicles according to the standards UIC 518 and EN 14363. The obtained results have shown that the proposed method can be successfully applied in solving the problem of high accuracy measurement of wheel–rail contact forces and contact point position using IWS.

Effect of vertical ground motion on earthquake-induced derailment of railway vehicles over simply-supported bridges

The running safety of railway vehicles on bridges can be negatively affected by earthquake events. This phenomenon has traditionally been investigated with only the lateral ground excitation component considered. This paper presented results from a numerical investigation on the contribution of vertical ground motion component to the derailment of vehicles on simply-supported bridges. A full nonlinear wheel–rail contact model was used in the investigation together with the Hertzian contact theory and nonlinear creepage theory, which allows the wheel to jump vertically and separate from the rail. The wheel–rail relative displacement was used as the criterion for derailment events. A total of 18 ground motion records were used in the analysis to account for the uncertainty of ground motions. The results showed that inclusion of vertical ground motion will likely increase the chance of derailment. It is recommended to include vertical ground motion component in earthquake induced derailment analysis to ensure conservative estimations. The derailment event on bridges was found to be more closely related to the deck acceleration rather than the ground acceleration.

車輪・レール間摩擦係数が分岐区間の走行安全性におよぼす影響のシミュレーション解析

The flange climb derailment of railway vehicle is caused by the phenomenon that the wheels climb up the rail when the lateral force gets excessive. In particular, the turnout has a structure that the flange climb derailment is likely to occur compared with the general track. In this paper, the running safety of turnout sections is analyzed using the multi-body dynamics analysis tool. As the results, it is showed that the first wheelset on the turnout of trailing direction should be especially noted in terms of the value of the wheel rise. It is also confirmed that the larger the friction coefficient is, the larger the value of the wheel rise.

Damage evaluation regarding to contact zones of high-speed train wheel subjected to thermal fatigue

Repetitive high frictional forces, induced from braking, and running of a train during railway service, generate high frictional temperature increment at the contact surface, as a result, thermal fatigue damage occurs at the surface of the wheel. Microscopic deformation in the wheel surface due to repetitive fatigue damage causes an initiation and propagation of thermal crack. That is, if the microscopic deformation is accumulated beyond the tolerance of the material resistances including the hardening of material and residual stress, then the surface will be damaged and fractured. As a result, the derailment of railway vehicle may possibly happen.In the present paper, we study on the failure analyses at the tread of the thermally damaged wheel by doing the metallurgical transformation analysis, hardness analysis, and the residual stress analysis to understand the failure mechanism of thermal fatigue damaged wheel. For this purpose, the microstructure of tread surface was examined by applying non-destructive replication method, and the hardness along the tread surface was measured. Also, the change in residual stress in the tread surface of new and thermal-damaged wheels was investigated. Meanwhile, FE analyses were performed considering the heat treatment process of wheel manufacturing, and the braking process during railway service. From the analysis results, we understand that the degree of metallurgical transformation is not the same even in the same tread surface, and residual stress measured turns into tensile stress from the compressive stress in manufacturing in the magnitude of approximately 118MPa in the thermal damaged surface wheel. The finite element analysis (FEA) data of residual stress considering heat treatment process of wheel is in good agreement with the experimental results measured in the wheel tread.

SELECTED PROBLEMS IN RAILWAY VEHICLE DYNAMICS RELATED TO RUNNING SAFETY

The paper includes a short review of selected problems in railway vehicle-track system dynamics which are related to the running safety. Different criteria used in assessment of the running safety are presented according to the standards which are in force in Europe and other countries. Investigations of relevant dynamic phenomena, including the mechanism of railway vehicle derailment, and the resulting modifications of the running safety criteria are also discussed.

Development of high-speed railway vehicle derailment simulation – Part II: Exploring the derailment mechanism

Based on the exactly solution for the wheel/rail contact point and the contact force, a vehicle/rail coupling model for analyzing dynamic derailment is developed in MATLAB as DDSHV (Dynamic Derailment Simulation for High-speed Vehicle). The calculation process of the simulation system is presented in detail, and the best solution conditions are also discussed to quickly obtain results. Two common types of dynamic derailment are studied in DDSHV. There exists a critical point in the process of wheel climb, and the dynamic weakening effect will promote the wheel-climbing rail. Meanwhile, some main factors, such as the speed, the rail condition and the wheel unload rate, have been studied on the dynamic weakening effect. The collision speed of the wheelset is the most important factor affecting impact derailment. As time becomes shorter, the collision can be investigated using LS-DYNA. The results confirm the equation for the critical impact speed used in this paper. DDSHV can also be used to find the vehicle running stability. Through the design of uplink and downlink algorithms, two critical running speeds, the critical speed and the nonlinear critical speed have been found. Yet, the changes in suspension parameters will directly influence these critical speeds. Therefore, an accurate configuration in vehicle will help to reduce the disturbances while an inaccurate configuration may lead to an incident. Although it is dangerous and difficult to make a derailment online test, the effectiveness of DDSHV has been verified by the known dynamic cases and lab tests. In conclusion, DDSHV has assisted in understanding the process of derailment, finding the important factors affecting derailment and exploring the mechanism of dynamic derailment.

Development of high-speed railway vehicle derailment simulation – Part I: A new wheel/rail contact method using the vehicle/rail coupled model

With an increase in speed, a vehicle’s dynamic behavior becomes apparent. Increasing speed not only affects the sitting comfort, but also may lead to derailment. However, an accident is difficult to predict, because the derailment mechanism is not thoroughly understood. The reliability of derailment simulations are completely conditional to being able to accurately solve the wheel and rail contact problem. Thus, an improved three-dimensional contact trace method is presented to quickly obtain the correct point. Then, a fast and accurate method for obtaining the contact force, which includes the creep force and the normal force, is improved. The results correspond more closely to realitic solutions compared with those of current methods. Next, a dynamic model of the vehicle and the rail is established. The two models are not independent of each other. The wheel–rail contact calculation is the key consideration for coupling in the two models. Finally, all the dynamic models, which are called dynamic derailment simulation for high-speed vehicle (DDSHV), are developed in MATLAB. To identify two different types of derailment, derailment judgment is embedded in the program package. The simulation system can be used to study the dynamic derailment mechanism, analyze derailment conditions and influence factors, and determine the key cause of the incident.

3403 曲線通過を考慮したジャイロダンパ付き一軸台車車両の検討(OS2-4 蛇行動に関するダイナミクス,OS2 交通・物流システムのダイナミクス,オーガナイズド・セッション(OS))

A railway vehicle wheel experiences the problem of hunting motion above a critical speed, which is caused by the contact force between the wheels and rails. The resonance is one of flutter-type self-excited oscillations and the growth of the response amplitude can lead to the derailment of railway vehicles. In our previous studies, a stabilization control method using a gyroscopic damper is proposed, which does not make the yawing motion mechanically stiffer. In this paper, an improved methods considering constant curve was proposed.

鉄道車両の乗り上がり脱線とその安全性評価( 運ぶ機械の信頼性・安全性)

鉄道車両の乗り上がり脱線とその安全性評価( 運ぶ機械の信頼性・安全性)

1C26 Stabilization of Hunting Motion by Gyroscopic Damper

A railway vehicle wheel experiences the problem of hunting motion above a critical speed, which is caused by the contact force between the wheels and rails. The resonance is one of flutter-type self-excited oscillations and the growth of the response amplitude can lead to the derailment of railway vehicles. In our previous studies, a stabilization control method using a gyroscopic damper is proposed, which does not make the yawing motion mechanically stiffer. In this paper, an improved method considering constant curve was proposed.

63877 Railway Vehicle Derailment Simulation for Derailment Detection System in Early Signs(Railroad System Dynamics)

63877 Railway Vehicle Derailment Simulation for Derailment Detection System in Early Signs(Railroad System Dynamics)

鉄道車両の走行安全性評価 : 輪重, 横圧, 脱線係数の計測

鉄道車両の走行安全性評価 : 輪重, 横圧, 脱線係数の計測

Influence of creep forces on the risk of derailment of railway vehicles

The derailment mechanism in a railway vehicle is a complex mechanical phenomenon which has been, and still is, the subject of intense research activity due to the serious consequences it can entail. Since Nadal deduced his well-known formula, many researchers have put forward alternative equations which all attempt to move closer to the data obtained experimentally. This paper provides a summary of the best known and draws up a new formulation based on the theoretical 3-D study of creep forces emerging from the contact patch of the wheel likely to derail. It also provides an in-depth analysis of the role played by spin creepage, including its effect on obtaining theoretical derailment limits, which are more realistic than those obtained using Nadal's formula. Finally, a new derailment criterion is proposed. This new criterion leads to less conservative values than Nadal's equation for zero yaw angles. When the yaw angle is high enough, the results obtained are coincident with those predicted by Nadal's equation.