Derailment Safety Research Articles

Derailment safety analysis for a tilting railway vehicle moving on irregular tracks shaken by an earthquake

The aim of this paper is to investigate the derailment of a tilting railway vehicle on curved tracks that are experiencing the twin effects of rail irregularities and an earthquake. The nonlinear governing differential equations of motion for a tilting railway vehicle are derived using a heuristic nonlinear creep model and Kalker’s linear theory. The tilting vehicle is modeled as a 24-degree-of-freedom system, with the lateral, roll and yaw motions of each wheelset, as well as the lateral, vertical, roll and yaw motions of the bogie frames and the car body all taken into account. The derailment quotients and offload factors of a tilting railway vehicle experiencing the twin effects of an earthquake on its wheelsets, bogie frames and car body in the lateral direction, and rail irregularities acting on its wheelsets in the lateral direction are investigated at various tilt angles. The obtained results show that, in general, a derailment quotient and an offload factor evaluated with an earthquake taken into consideration are larger than those obtained without consideration of the earthquake. Moreover, the derailment quotient and offload factor of a wheelset increase with an increase in the tilt angle of the railway vehicle experiencing excitations from an earthquake and also rail irregularities. Finally, the effects of suspension parameters on the derailment quotient and offload factor of a wheelset are investigated. Taken together, it is clear that the influences of rail irregularities and an earthquake on the derailment of a tilting railway vehicle cannot be disregarded.

Research on the Unsteady Influence Model of the Heavy Haul Train for Safe Running

Based on platform of the train air brake and longitudinal dynamics simulation, the longitudinal force transmission model in natural coordinate system is established. The position coordinates of vehicles on the line are obtained, is adopted the two-dimensional approximation method to solve the center plate coordinates. The position vectors from wagon body and couplers are constructed, so the size and direction of coupler angles are solved with vector product and number vector after. Again based the action of force from buffers and couplers, are solved lateral and vertical force components from couplers. Then the moment balance principle is applied to establish the quasi static vehicle model. And are referenced single wheel set derailment evaluation indexes on the train safety assessment. The train of a single series of 10 000 t on Datong-Qinhuangdao line is simulated, and train brake, line running conditions, the train running speed and other factors are analyzed on the safety indexes. Generating mechanism of the non steady coupler force is analyzed. The research results are provided new idea and reference for safe train operation. The system can simulate to calculate the data of train braking, longitudinal impulse, derailment safety index, and show it simultaneously.

레일 경좌 변화에 따른 곡선부 통과열차의 주행안전성 해석

So far today, there is a speed limit by the radius of curve based on operation regulation in domestic railway, however a study for the maximum running speed at the curved section without any derailment would be necessary. The two major factors related to the running safety of railway vehicle are classified as the railway vehicle condition and the track condition. In terms of the rail inclination among many other factors, the determination of rail inclination within the possible limit is necessary for the geometrical structure of the optimum track. The disregard of the geometrical parameter related to the rail inclination may cause a serious problem to the running safety of railway vehicle. This study is focusing on the analyzing of running safety regard to the change of rail inclination among the many other parameters to improve derailment safety, so that there is an affection analysis of the running safety regard to the change of rail inclination in the ideal and geometric track condition. Also There is an affection analysis of the running safety regard to the simultaneous change of rail inclination and the running speed at the curved section. According to analysis results of running safety, In case that the left and right rail inclination are 1/40, the running safety of this condition defined than other conditions. Also, the rail inclination of conventional lines is 1/40, Therefore, the railway vehicle passing through curve is safe when the railway vehicle runs in conventional lines.

기존선 구간(동대구-남성현)에서의 탈선안전도 해석 연구

기존선 속도향상 시에 탈선안전도를 고려한 기존선 구간 (동대구-남성현) 최대 운행가능속도에 대 한 기준을 제시하여 기존선의 곡선부 및 완화곡선부 통과 시 속도를 향상시키고자 한다. 본 연구에서는 탈선의 위험도가 높은 곡선부 통과하는 열차의 고속향상을 도모하기 위하여 실제 선로조건인 동대구-남 성현 상·하행 구간에서의 곡선부 구간별 통과 시 탈선안전도에 미치는 영향을 살펴보았다. 곡선반경별 주행속도를 실제 선로 조건에서의 기존 속도 대비 5-20% 향상시켜 탈선안전도 해석을 수행하였다.

실제 선로조건에 따른 DMT 화차의 탈선안전도 평가

The DMT freight is judged that economic performance is good because can increase cargoes than existing freight. However, the existing freight cars, each with a different balance to the body structure is bogie because the vibrations may occur. Thus, by minimizing vibration over the existing freight securing the safety of the driving if you will not have major problems in cargoes. In this study, multi-body dynamic analysis tool, VI-Rail using the actually Gyeongbu Railroad line and an empty, full freight condition include curve radius, track irregularity, The DMT freight of the derailed wagons were assessed for safety analysis. Full and empty freight conditions for parity in the Gyeongbu Railroad line(Dongdaegoo<TEX>${\leftrightarrow}$</TEX>Kyungsan) derailment safety analysis, such as derailment coefficient and the wheel unloaded, echoing the curve and the orbit is affected by the irregularity was found. Full freight condition than the empty conditions showed a significant derailment safety. Overall, the limits of derailment coefficient(Q/P = 0.8) and wheel unload decrement limits(<TEX>${\triangle}P/P$</TEX> = 0.6) is less safe with me confirmed that the derailment safety.

Assessment of safety against derailment using simulations and vehicle acceptance tests: a worldwide comparison of state-of-the-art assessment methods

The assessment of derailment safety of new railway vehicle designs is a fundamental concern worldwide. Although the methods used for assessment in different countries and regions vary considerably, the fundamental mechanisms being addressed are the same. This paper provides a detailed review of the current state-of-the-art methods for derailment safety assessment in several regions and countries including Europe, UK, USA, and Russia. Brief overviews of the methods used in China, Korea, and Japan are also included. Similarities and differences are discussed, including testing and computer simulations. References are provided for the origins of the methods and safety performance criteria used in each region. Recommendations are made for improving the assessment methods, especially the use and validation of computer simulations.

Dynamic Analysis for Derailment Safety of High-Speed Railway Vehicle Bogies

Based on the heuristic nonlinear creep model, the nonlinear coupled differential equations of the motion of a 12 degree-of-freedom (12-DOF) bogie system which takes account of the lateral displacement, vertical displacement, the roll angle and the yaw angle of the each wheelset and the bogie frame, moving on curved tracks are derived. The nonlinear creep forces and moments are constructed via the saturation constant of the nonlinear creep model in completeness. The effect of the suspension parameters of a bogie system on the derailment quotient is investigated. Results obtained in this study show that the derailment quotient of a bogie system increases as the vehicle speed increases. In addition, the derailment quotient of a bogie system is generally decreased with the increasing values of suspension parameters.

틸팅차량의 준 정적상태 전복 안전성과 탈선 안전성에 관한 연구

This study presents a method to evaluate overturning safety and derailment safety of korean tilting train using kinematic analysis of four-bar linkage tilting mechanism. The safety is evaluated considering tilting vehicle body CG displacement. The design sensitivity for stable and safe maximum speed is evaluated around current korean tilting train design data. The current design shows minimum center of gravity displacement. Higher speed can be achieved with larger center of gravity displacement.

Wheel Rail Lateral Impact and Derailment Safety Assessment

Wheel Rail Lateral Impact and Derailment Safety Assessment

Freight car models and their computer-aided dynamic analysis

Computer models of freight cars with three-piece and Y25 bogies are considered and compared. Efficient numeric methods for simulation of vehicle models in the presence of frictional contacts are discussed. Some simulation results on derailment safety analysis and influence of track gauge value on freight-car dynamics are presented. Methods of stress loading and durability analysis based on computer simulation and some results are presented. A tribodynamic model of railway vehicle-track interaction and results of computation of wheel and rail profile wear are discussed.

Study on the wheel/rail interaction and derailment safety

The wheel flange climb derailment and wheel impact derailment are studied. Firstly, it is assumed that the wheel flange climb process is quasi-static, then the flange climb derailment criteria are derived through analyzing the forces exerted on the wheelset. One criterion is the classical derailment formula that assumes friction sliding between wheel and rail occurs. Another is the so-called approximate analytical formula that considers the effect of wheel/rail creep forces. The calculations of an example indicate that the results of the classical method are more conservative compared with the results of the analytic method for the diagnosis of wheelset derailment. The laboratory test for the flange climb derailment with a single wheelset test stand is also undertaken to validate the theoretical analysis. Secondly, the wheel impact derailment, a kind of dynamic derailment, is investigated. The analytic solutions for the tangential motion of the wheel/rail contact point and the jumping height of the wheel are derived. The derailment criteria by using the wheel jumping height and the lateral impact force to wheel vertical load ratio are given. The influences of wheelset lateral impact velocity, flange angle, wheel/rail friction coefficient, wheel vertical load and impact time interval on wheelset derailment are analyzed.

Derailment Safety Evaluation by Analytic Equations

A quicker method for calculating the likelihood of flange-climb derailment is proposed in this paper. This method uses analytically calculated lateral and vertical wheel loads based on analytic equations and measured data. The traditional derailment coefficient, lateral force divided by wheel load, also known as Q/P in Japan, takes too long to estimate with time-series computer simulations. This research evaluates equations developed to estimate Q/P more rapidly. Among the elements are: the effect of centrifugal force on wheel load and the effects of track twisting and shifting among others. The calculation that is proposed considers wheel flange angle, equivalent friction coefficient and the wheel's angle of attack. More work needs to be done to refine the method and expand it to more situations. This calculation is only for bolster-less bogies with air spring secondary suspension.

On the New Air Spring Control System for Railway Vehicles.

A new air supply / exhaust control system was developed for pneumatic suspension of railway vehicle. This system which equalizes unbalanced inner pressure of air spring and horizontalizes the vehicle floor when the vehicle is slowed or stopped. It counters such defects experienced in the conventional leveling valve (LV) system as large unbalance of air spring inner pressure when stopping at distorted track of transient curve that might cause wheel unloading and decrease the derailment safety margin. The new control system is composed of solenoid valves, height and pressure sensors, clinometer and controller (CPU). Major control laws are (1) detect forced deflection of air spring caused by track distortion, (2) equalize the air spring height distortion when running, (3) horizontalize vehicle when slowed or stopped, and (4) equalize air spring pressure unbalance. These functions are implemented in a computer program.

Magnetic Guidance of Conventional Railroad Vehicles

The potential for improved dynamic performance of conventional rail vehicles through control of linear induction or synchronous motors is explored. Improvements in vehicle stability, ride quality, traction capability, track loading, derailment safety, and curving performance result from use of controllable lateral and normal forces present in the motor. Recent advances in technology originally developed for high-speed levitated vehicles are applied to conventional railroad systems which have a greater potential for near-term implementation. The dynamic performance of alternate configurations, consisting of several generic motor types mounted either on trucks or carbodies, are evaluated. Significant improvements in both lateral dynamic stability and curving performance may be realized through magnetic guidance of the trucks using force levels well within the capability of existing linear motor technology.

Derailment Mechanics and Safety Criteria for Complete Rail Vehicle Trucks

Derailment Mechanics and Safety Criteria for Complete Rail Vehicle Trucks

Evaluation of Time-Duration Dependent Wheel Load Criteria for Wheelclimb Derailment

The most widely accepted criterion for wheelclimb derailment defines an upper limit for safe operation on wheel/rail contact forces on the climbing wheel, with the limit varying with time duration of the forces. For dynamic wheelclimb processes with significant lateral velocities, lateral forces may be measured for short time durations that are larger than those that may be sustained without derailment in steady state. This paper shows, however, that the JNR and other time-duration dependent criteria based on wheel load measurements alone are unsuccessful in predicting derailment safety. For wheelclimb processes involving negligible lateral velocities, the derailment limit can be estimated from quasisteady analysis of wheel/rail forces. The evaluation of criteria is based on experiments with a single wheelset and a nonlinear theory for dynamic wheelclimb.