Running Safety Of Railway Vehicles Research Articles

Virtual point tracking method for online detection of relative wheel-rail displacement of railway vehicles

Relative wheel-rail displacement (RWRD) is an important physical quantity that responds to the hunting stability and running safety of railway vehicles but detecting this physical quantity is challenging during train operation due to the complex service environment and the nonlinearity of vehicle-rail system. To address this problem, this paper proposes a virtual point tracking (VPT) method to detect RWRD. First, a series of regions of interest (ROIs) in the preprocessed wheel-rail contact images are extracted using a simplified YOLO (SYOLO) model. Then, some key positions of the wheel and rail on the extracted ROIs are identified using an improved UNet (IUNet) model and characterized by virtual points. Finally, the global coordinates of the virtual points in the whole wheel-rail contact image are calculated to obtain the final RWRD. To demonstrate the feasibility of the VPT method, it is used to detect the RWRD of a vehicle operating on a full-scale roller rig. For comparison, the original UNet model is directly used to detect the RWRD. Two quantities, Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), are applied for quantitative analysis and the results show that the VPT method can identify the RWRD more reliably and accurately.

A Code-Type Method to Assess the Running Safety of Railway Vehicles on Bridges Shaken by Earthquakes Including Girder’s Torsional Motion

The safety of railway vehicles running on bridges needs to be evaluated in the seismic design of bridges. This study examined the spectral intensity calculated from the lateral vibration of the bridge deck during earthquakes, a Japanese code-based index to measure bridge vibration’s strength. In addition, the effect of the torsion of the bridge deck on vehicle derailment is investigated using a nonlinear vehicle–track–bridge model. The bridge deck torsion increases the derailment risk, especially for bridges with a low natural frequency. The reason lies in that the lateral and torsional deck motions are highly correlated for bridges with lower frequency. Based on this observation, a code-type formula was proposed to evaluate the vehicle running safety including both lateral and torsional motions of the bridge deck. The accuracy of the proposed formula was demonstrated by comparison with vehicle–track–bridge simulation excited by ground motion records. The new procedure overcomes the non-conservative assessment of derailment caused by ignoring bridge torsion.

Algorithm for inverse determination of derailment coefficient by using instrumented wheelsets

The main indicator of the running safety of railway vehicles is the ratio between lateral and vertical forces in the wheel-rail interaction, known as derailment coefficient. Its exact determination has a huge significance in the development and certification phases of railway vehicles. The most reliable determination of wheel-rail interaction forces is based on experimental testing, by using instrumented wheelsets, which is otherwise prescribed in appropriate international regulations. This paper presents a unique algorithm for inverse determination of wheel-rail interaction forces, i.e., derailment coefficient, based on the measurement signals obtained from instrumented wheelsets. The blind signal separation (BSS) and method of independent component analysis (ICA) are applied. Verification is carried out on the example of the wheelset of freight wagon, based on the wheel's FEM model. The obtained results confirmed a high efficiency and accuracy of the developed algorithm, whereby estimated error of inverse identification is less than 5%.

Effects of dent size on the evolution process of rolling contact fatigue damage on defective rail

Defects such as dents on the rail surface might induce severe rolling contact fatigue (RCF) and then threaten the running safety of railway vehicles. This study aims to explore the initiation and propagation of RCF cracks around dents with different sizes through observing both surfaces and cross-sections of the defective rail. The experiments are conducted on a wheel/rail twin-disc machine. Results indicate that the microstructure evolution process around the dent can be divided into three main stages, namely crack initiation, crack propagation and dent removal. Dents in different sizes act very similarly in each stage, including the position, the crack growth path and the final appearance after the dent has been fully worn off. However, dents in different sizes cause different lifetimes of crack initiation and different lasting times of dents at each stage. For the lager dent, cracks initiate later but propagate for a longer time period, so the dent size plays an important role in the RCF evolution process.

Study on the Improvement of Running Safety of Railway Vehicles with Yaw Damper during an Earthquake

Study on the Improvement of Running Safety of Railway Vehicles with Yaw Damper during an Earthquake

A Kalman filter algorithm for identifying track irregularities of railway bridges using vehicle dynamic responses

Track irregularities affect the running safety of railway vehicles and ride comfort, hence track irregularity identification using the dynamic responses of in-service vehicles is of great interest. Because the high-speed rail lines mainly consist of bridges in China, vehicle-bridge (VB) interactions which significantly influence the vehicle dynamic responses should be taken into account in the track irregularity identification. This paper proposes a Kalman filter algorithm to identify the track irregularities of railway bridges using vehicle dynamic responses considering the VB interactions in real-time. A state space model is established to represent a time-dependent VB system subjected to unknown track irregularity excitations. A Kalman filter algorithm is proposed to estimate optimally the state vector of the VB system and to identify the track irregularities subsequently. Two numerical examples including a real railway bridge constructed in China are presented to validate the accuracy of the proposed algorithm. A parametric study is also conducted to demonstrate the effects of measurement noise, vehicle running state, parameter uncertainty and model uncertainty on the identification of track irregularities. Comparison results demonstrate that the proposed track irregularity identification algorithm outperforms the conventional approaches mainly because of considering the VB interaction. The proposed algorithm enables efficient monitoring the track irregularities of railway bridges using the acceleration responses of in-service vehicles.

<b>Recent Research and Development Activities in Vehicle Technology</b>

RTRI was involved in approximately 280 research themes in the fiscal year 2017 to 2018. Among them, 46 were related to rolling stock technology, covering a wide range of themes, in practical, applied and fundamental research, such as: the increase in train running speed and improvement of ride comfort, the applied research such as the running stability and reliability of rolling stock, and elucidation of the mechanisms leading to wheel wear. Three topics from this research and described in this paper are: "Quantitative evaluation of wheel flats affecting vehicle bogie behavior," "Development of a 3-Dimentional measurement device for wheel profiles" and "Evaluation of the running safety of railway vehicles in case of air spring deflation."

궤도상 국부적인 위치에서의 차륜레일 마찰계수 변화가 차량 주행안전성에 미치는 영향 해석

궤도상 국부적인 위치에서의 차륜레일 마찰계수 변화가 차량 주행안전성에 미치는 영향 해석

3호선 실제선로 조건에서의 레일경좌 변화에 따른 철도차량 주행안전성 해석

It is very hard to analyze the train derailment safety quantitatively at the curved section because of the diversified affect parameters including the complex interaction between wheel and rail, the train conditions such as the shape of wheel, suspension system, the track conditions such as the radius of curve, cant, transition curve, and the operation conditions, etc. Two major factors related to the running safety of railway vehicle are classified as the railway vehicle and the track condition. In this study, when the railway vehicle passing through curves of actual track condition of subway line NO.3 in seoul (<TEX>$Yeonsinnae{\leftrightarrow}Gupabal$</TEX>), the effect that has influence on running safety depending on rail inclination. The analysis result of 1/40 rail inclination condition is more favorable on running safety than other rail inclination conditions because derailment coefficient and wheel unloading ratio are the lowest.

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

The wheel–rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel–rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel–rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel–rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of railway vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel–rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel–rail vertical force. In addition, use of the method to determine the high-frequency wheel–rail interaction forces reveals that it is possible to identify the high-frequency wheel–rail forces through the accelerations on the axle box.

鉄道台車のモーメントに着目した横圧推定式の検討

When railway vehicles pass through a sharp curve, yaw moment is generated at the bogie. This condition affects the increase of the lateral force of the outside wheel of the front axle of the leading bogie, which is important factor for assessing the running safety of railway vehicles. A Lateral-force/Wheel-load estimation equation has been developed as a method to calculate the lateral force and the wheel load during the curve passage of railway vehicles taking into account the yaw moment of the bogie. This equation is useful to estimate the risk of flange-climb derailment. The authors have newly suggested a more versatile Lateral-force/Wheel-load estimation equation with a focus on the improvement of the estimation of yaw moment of the bogie. Running tests using test track which has sharp curves were carried out to measure the generated forces of several components of the bogie, which are the sources of the yaw moment of the bogie. New equations were produced based on the test results, and compared with the measured lateral forces and wheel loads.

Dynamic analysis of the influence of the friction coefficient of the wheel tread on the running safety of railway vehicle

Dynamic analysis of the influence of the friction coefficient of the wheel tread on the running safety of railway vehicle

&lt;b&gt;Development of the Crushable Stopper as Bogie Parts for Countermeasures against Derailment in Case of Earthquake&lt;/b&gt;

A crushable lateral displacement stopper has been developed whose gap from the center pin expands only when it receives a strong impact in case of a major earthquake. As a countermeasure to improve the running safety of railway vehicles during earthquakes the stopper is used together with a specialized lateral damper. This paper describes the crushable stopper and results of static load tests and shaking tests on the large shaking test facility of RTRI with a full-scale vehicle model consisting of one bogie and half a carbody.

&lt;b&gt;Dynamic Simulations of Railway Vehicles Running on Tracks with Lateral and Roll Vibrations&lt;/b&gt;

This study investigates the effects of track rolling vibrations on the running safety of railway vehicles. During earthquakes, viaducts are subject to rolling vibrations in addition to lateral and vertical directions, causing tracks on viaducts also to vibrate in the rolling direction. A vehicle dynamics simulator (VDS) was modified to enable simulation of rolling vibrations on a track. Sinusoidal oscillation analysis showed that running safety decreased as the ratio of the roll amplitude to the lateral amplitude of the track increased. In addition, it was verified that the decrease in running safety due to the rolling vibration of the track on rigid-frame viaducts was smaller than for pier type viaducts. This is because rolling vibrations on rigid-frame viaducts are smaller than on pier type viaducts.

1417 鉄道台車のモーメントに着目した横圧推定式の検討

When railway vehicles pass through a sharp curve, yaw moment is generated at the bogie. This moment affects the lateral force of the outside wheel of the front axle of the leading bogie, which is important factor for assessing the running safety of railway vehicles. A Lateral-force/Wheel-load estimation equation has been developed as a method to calculate the lateral force and the wheel load during the curve passage of railway vehicles taking into account the yaw moment of the bogie. This equation is useful to estimate the risk of flange-climb derailment. The authors have newly suggested a more versatile Lateral-force/Wheel-load estimation equation with a focus on the improvement of the estimation of yaw moment of the bogie. Running tests using test track which has sharp curves were carried out to measure the generated forces of several components of the bogie, which are the sources of the yaw moment of the bogie. New equations were produced based on the test results, and compared with the measured lateral forces and wheel loads.

Evaluation of Running Safety for Railway vehicles Based on Vibration Acceleration of Bogie

The lexical meaning of derailment shall be the wheels of trains going off the track and it is an important factor for the running safety of railway vehicles. For the measurement of interaction forces between the wheel and the rail, wheel set is used with normal method and the vibration accelerometer is used with simplified method to assess the safety of a railway vehicle in the derailment process. The result has been recorded by measuring vibration acceleration.

실제 선로조건에서의 레일 경좌 변화에 따른 철도차량의 주행안전성 해석

Railways are currently subject to the enforcement of speed limits for each curve as prescribed by the Railway Operating Rules in Korea. However, research is required to determine the maximum speed of trains passing through each curve that allows them to run without the risk of derailment in relation to the speed enhancement of existing railway tracks. In addition, factors affecting the running safety of railway vehicles can be classified into those in terms of vehicle aspects and those in terms of track aspects. This study sought to analyze the running safety of railway vehicles according to changes in the inclination of the rail from among the factors affecting the enhancement of safety against derailment. To increase the speed of trains passing through curves that have high derailment risk, this study also analyzed the running safety of railway vehicles according to the inclination of the rail and changes in running speed while a vehicle passes through each curve section in both the up and the down train line sections between Namsunghyun and Chungdo, which represent the actual conditions of railway tracks.

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.

2306 左右およびロール振動を伴う軌道を走行する車両挙動解析(OS2-2 鉄道と無人ヘリのダイナミクス,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))

In this study, the effects of the roll vibration of the track on the running safety of railway vehicles are investigated. The roll vibrations of the top of the viaducts are caused by earthquakes. The vehicle dynamics simulator (VDS) is modified to be able to input roll vibration of the track. According to the sinusoidal oscillation analysis, the running safety of railway vehicle is decreased by approximately 10% when the ratio between the roll amplitude and the lateral amplitude of the track vibration is 0.02 rad/m. In addition, it is verified that the decreasing of the running safety due to roll vibration of the track in case of the rigid-frame structure is smaller than that in case of the pier structure. This is because that the roll vibration of the rigid-frame structure is smaller than that of the pier structure.

철도차량용 차륜 플레이트에서의 새로운 횡압 계측방법

Conventionally, to measure derailment coefficient of a railway wheel, strain gauges for lateral force measurement are attached to both side of the wheel. But narrow gap between railway wheel and traction motor makes it difficult to attache the strain gauges at the inner side of wheel. In this study, to overcome the hard accessibility to the strain gauge points by narrow gap, a new Wheatstone bridge connection method is presented by attaching all the strain gauges at the outer side of wheel with a new bridge connection. We evaluate the running safety of railway vehicles in accordance with railway safety regulations. The experimental results obtained shows higher sensitivity than conventional methods and the derailment coefficient measurement procedure becomes simpler.