Pub Date : 2024-08-27DOI: 10.1177/09544097241277577
Hassan Liravi, Amin Khajehdezfuly, Javad Sadeghi, Peyman Aela, Yazdan Shafieyoon, Amir A. Shiraz
Despite the recent surge in the construction of ballastless railway tracks, there exists a notable research gap concerning the rail seat load (RSL) associated with these track types. The RSL is the load transferred from the rail to the fastening system, the plate beneath the rail and the rail pad. The prediction of RSL in ballasted track systems is widely investigated, however, there has been a relative lack of research into the ballastless railway track systems. In this paper, a 2D finite element model (2D FEM) was adopted to evaluate the RSL concerning the effective parameters, including sleeper spacing, fastening system stiffness and the flexural modulus of the rail. The numerical model was validated through a field test performed in the study. Moreover, a mathematical expression was proposed to determine the RSL ratio for concrete slab tracks. The RSL directly correlates with the sleeper spacing and the fastening stiffness, while this relation with the flexural rigidity is inverse. Based on the results, it was found that the RSL ratio obtained from the conventional methods differed considerably from the proposed mathematical expression. More specifically, this difference was observed in almost all of the values in the sleeper spacing and flexural rigidity of rail for the Kerr model except 0.68 m and 5 MN.m2, respectively.
{"title":"Numerical investigation on loading pattern of railway concrete slabs","authors":"Hassan Liravi, Amin Khajehdezfuly, Javad Sadeghi, Peyman Aela, Yazdan Shafieyoon, Amir A. Shiraz","doi":"10.1177/09544097241277577","DOIUrl":"https://doi.org/10.1177/09544097241277577","url":null,"abstract":"Despite the recent surge in the construction of ballastless railway tracks, there exists a notable research gap concerning the rail seat load (RSL) associated with these track types. The RSL is the load transferred from the rail to the fastening system, the plate beneath the rail and the rail pad. The prediction of RSL in ballasted track systems is widely investigated, however, there has been a relative lack of research into the ballastless railway track systems. In this paper, a 2D finite element model (2D FEM) was adopted to evaluate the RSL concerning the effective parameters, including sleeper spacing, fastening system stiffness and the flexural modulus of the rail. The numerical model was validated through a field test performed in the study. Moreover, a mathematical expression was proposed to determine the RSL ratio for concrete slab tracks. The RSL directly correlates with the sleeper spacing and the fastening stiffness, while this relation with the flexural rigidity is inverse. Based on the results, it was found that the RSL ratio obtained from the conventional methods differed considerably from the proposed mathematical expression. More specifically, this difference was observed in almost all of the values in the sleeper spacing and flexural rigidity of rail for the Kerr model except 0.68 m and 5 MN.m<jats:sup>2</jats:sup>, respectively.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"3 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142207386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1177/09544097241278012
Wangyang Liu, Qingsheng Feng, Hong Li
Prolonged vibration can be uncomfortable for passengers utilizing urban rail transit systems. This study proposes an automatic speed control framework for urban railway trains to reduce vertical vibrations experienced by passengers. We suggest the concept of the “segmented comfort speed limit” to represent the vertical passing comfort of oncoming sections. This speed limit is calculated from 1/3 octave band acceleration and smoothed through lag-type speed control mode. The deep deterministic policy gradient algorithm with hindsight experience replay mechanism (HER-DDPG) is designed, to balance safety, comfort, and energy efficiency driving. Verify the speed control framework based on HER-DDPG through the rail data collected from Dalian Metro Line 12. Compared with the DDPG-based model, the vertical comfort is improved by 2.34%, and the longitudinal acceleration and total energy consumption are reduced by 45% and 8.1%. Compared with the real-world train control trajectory, HER-DDPG improves vertical comfort by 9.76% and reduces energy consumption by 12.4%. The results show that the proposed framework can effectively improve the ride experience of passengers.
{"title":"Optimizing passengers’ experience: A goal-oriented reinforcement learning speed control approach for urban railway trains","authors":"Wangyang Liu, Qingsheng Feng, Hong Li","doi":"10.1177/09544097241278012","DOIUrl":"https://doi.org/10.1177/09544097241278012","url":null,"abstract":"Prolonged vibration can be uncomfortable for passengers utilizing urban rail transit systems. This study proposes an automatic speed control framework for urban railway trains to reduce vertical vibrations experienced by passengers. We suggest the concept of the “segmented comfort speed limit” to represent the vertical passing comfort of oncoming sections. This speed limit is calculated from 1/3 octave band acceleration and smoothed through lag-type speed control mode. The deep deterministic policy gradient algorithm with hindsight experience replay mechanism (HER-DDPG) is designed, to balance safety, comfort, and energy efficiency driving. Verify the speed control framework based on HER-DDPG through the rail data collected from Dalian Metro Line 12. Compared with the DDPG-based model, the vertical comfort is improved by 2.34%, and the longitudinal acceleration and total energy consumption are reduced by 45% and 8.1%. Compared with the real-world train control trajectory, HER-DDPG improves vertical comfort by 9.76% and reduces energy consumption by 12.4%. The results show that the proposed framework can effectively improve the ride experience of passengers.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"14 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-16DOI: 10.1177/09544097241272753
Yaodong Fu, Muzi Wang, Dabin Cui, Ping Lu, Xinyi Li, Tao Liu
Wheel polygonal wear is one of the most serious problems in the railway industry nowadays. To study the mechanism of wheel polygonal wear, the wear prediction model was established. The three-dimensional wheel profile model and the improved USFD wear prediction algorithm were used to research the wear state of the wheel. The vehicle system dynamic characteristics and wheel wear state under different running speeds are studied. The results show that the vibration state of the wheel will be affected by the vertical and lateral coupling vibration of the wheel when considering the three-dimensional wheel polygonal wear. Due to the influence of coupled vibration, the wheel will appear larger wheel-rail force fluctuation points at different phase angles. The large wheel-rail force fluctuation at these different phase angles is one of the reasons for the formation of wheel polygonal wear. At the same time, the natural mode of the vehicle system will also affect the order of the wheel polygon and the amplitude of the wheel polygon. This study provides a new idea for the research of the wheel polygon mechanism.
{"title":"The mechanism of polygonal wheel wear considering a three-dimensional profile","authors":"Yaodong Fu, Muzi Wang, Dabin Cui, Ping Lu, Xinyi Li, Tao Liu","doi":"10.1177/09544097241272753","DOIUrl":"https://doi.org/10.1177/09544097241272753","url":null,"abstract":"Wheel polygonal wear is one of the most serious problems in the railway industry nowadays. To study the mechanism of wheel polygonal wear, the wear prediction model was established. The three-dimensional wheel profile model and the improved USFD wear prediction algorithm were used to research the wear state of the wheel. The vehicle system dynamic characteristics and wheel wear state under different running speeds are studied. The results show that the vibration state of the wheel will be affected by the vertical and lateral coupling vibration of the wheel when considering the three-dimensional wheel polygonal wear. Due to the influence of coupled vibration, the wheel will appear larger wheel-rail force fluctuation points at different phase angles. The large wheel-rail force fluctuation at these different phase angles is one of the reasons for the formation of wheel polygonal wear. At the same time, the natural mode of the vehicle system will also affect the order of the wheel polygon and the amplitude of the wheel polygon. This study provides a new idea for the research of the wheel polygon mechanism.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"7 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142207387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-13DOI: 10.1177/09544097241272888
Rong Chen, Hui Peng, Kai Liu, Juzhen Liu, Junfeng Li, Jianxing Liu, Ping Wang
The rapid development of high-speed railway bridges in China has brought enormous challenges to the ballast bed stability on the bridge. With the increase in the bridge span, the bridge deformation under the temperature load increases gradually, as well as the stability difference of ballast bed between different regions. Moreover, the track vibration response under high-speed driving conditions is larger, which can easily cause differential settlement, flying ballast, and deterioration of the ballast bed, thereby affecting the bearing capacity and stability of the ballast bed. In view of this, this article summarizes relevant research work on a ballast bed on the bridge from the perspectives of the resistance, deformation, and acceleration response of the ballast bed. In addition, this study discusses the existing measures for improving the ballast bed stability on the bridge, including the optimization of the sleeper and ballast bed structures. Finally, the main issues that need to be addressed to improve the ballast bed stability on the bridge are pointed out, and ideas for future research on ballast beds on bridges with different spans and structures are proposed.
{"title":"Advances in research on the ballast bed stability on railway bridges","authors":"Rong Chen, Hui Peng, Kai Liu, Juzhen Liu, Junfeng Li, Jianxing Liu, Ping Wang","doi":"10.1177/09544097241272888","DOIUrl":"https://doi.org/10.1177/09544097241272888","url":null,"abstract":"The rapid development of high-speed railway bridges in China has brought enormous challenges to the ballast bed stability on the bridge. With the increase in the bridge span, the bridge deformation under the temperature load increases gradually, as well as the stability difference of ballast bed between different regions. Moreover, the track vibration response under high-speed driving conditions is larger, which can easily cause differential settlement, flying ballast, and deterioration of the ballast bed, thereby affecting the bearing capacity and stability of the ballast bed. In view of this, this article summarizes relevant research work on a ballast bed on the bridge from the perspectives of the resistance, deformation, and acceleration response of the ballast bed. In addition, this study discusses the existing measures for improving the ballast bed stability on the bridge, including the optimization of the sleeper and ballast bed structures. Finally, the main issues that need to be addressed to improve the ballast bed stability on the bridge are pointed out, and ideas for future research on ballast beds on bridges with different spans and structures are proposed.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"61 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142207388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Following the extensive use of resilient wheels on trams, several subways in China have started pre-launch testing of resilient wheels. While it remains at an early stage, the long-term behavior of the wheel has become a great concern for subway operators and wheel suppliers. To address the concern, this study focuses on derailment risk by evaluating the allowed maximum amplitudes of low-order polygonal wear on resilient wheels. Firstly, a metro vehicle-track dynamic system model equipped with resilient wheels is built. Then, based on the operation safety index and current re-profiling regulations for conventional wheels, the influence of wheel axial and radial stiffness on the radial amplitude limits of resilient wheel polygonal wear is analyzed. To perform the analysis, firstly the commonly-used stiffness for a resilient wheel (300 kN/mm in radial direction and 50 kN/mm in axial direction) is adopted to study the effect of resilient wheel polygonization on wheel load reduction ratio. Then, wheel load reduction ratio is predicted for different radial (up to 600 kN/mm) and axial (up to 100 kN/mm) stiffnesses of the resilient wheel and different orders (up to 10) of wheel polygonization of 1 mm amplitude. A contour plot is provided to illustrate how the wheel load reduction ratio varies with the harmonic order and amplitude of wheel polygonization under different combinations of resilient wheel’s equivalent axial and radial stiffnesses. It is found that, with the increase of the amplitude of the polygonal wear of a certain harmonic order on resilient wheel, the number of the available combinations of the equivalent stiffnesses adopted by the resilient wheel becomes less by considering the operation safety indexed with wheel load reduction ratio. Besides, depending on the stiffness of the resilient wheel, the allowed amplitude corresponding to the polygonization of each order has been suggested with the contour plots.
{"title":"Study on the allowed maximum amplitudes of low-order polygonal wear on resilient wheels based on operational safety","authors":"Shuoqiao Zhong, Xin Zhou, Xiaozhen Sheng, Chuanlun Hou, Yuan Qi, Luis Baeza","doi":"10.1177/09544097241272809","DOIUrl":"https://doi.org/10.1177/09544097241272809","url":null,"abstract":"Following the extensive use of resilient wheels on trams, several subways in China have started pre-launch testing of resilient wheels. While it remains at an early stage, the long-term behavior of the wheel has become a great concern for subway operators and wheel suppliers. To address the concern, this study focuses on derailment risk by evaluating the allowed maximum amplitudes of low-order polygonal wear on resilient wheels. Firstly, a metro vehicle-track dynamic system model equipped with resilient wheels is built. Then, based on the operation safety index and current re-profiling regulations for conventional wheels, the influence of wheel axial and radial stiffness on the radial amplitude limits of resilient wheel polygonal wear is analyzed. To perform the analysis, firstly the commonly-used stiffness for a resilient wheel (300 kN/mm in radial direction and 50 kN/mm in axial direction) is adopted to study the effect of resilient wheel polygonization on wheel load reduction ratio. Then, wheel load reduction ratio is predicted for different radial (up to 600 kN/mm) and axial (up to 100 kN/mm) stiffnesses of the resilient wheel and different orders (up to 10) of wheel polygonization of 1 mm amplitude. A contour plot is provided to illustrate how the wheel load reduction ratio varies with the harmonic order and amplitude of wheel polygonization under different combinations of resilient wheel’s equivalent axial and radial stiffnesses. It is found that, with the increase of the amplitude of the polygonal wear of a certain harmonic order on resilient wheel, the number of the available combinations of the equivalent stiffnesses adopted by the resilient wheel becomes less by considering the operation safety indexed with wheel load reduction ratio. Besides, depending on the stiffness of the resilient wheel, the allowed amplitude corresponding to the polygonization of each order has been suggested with the contour plots.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"22 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-23DOI: 10.1177/09544097241266915
Longfei Chen, Yong Wang, Huailong Shi
Due to coupling with carbody suspension modes in railway vehicles, primary hunting can lead to significant low frequency swaying of the carbody, severely deteriorating ride quality. In order to address this issue, this paper conducts a detailed investigation into the coupling effect between suspension modes and hunting modes of metro vehicles. Initially, a simplified lateral dynamics model is established, and a continuous modal tracking method is adopted for track suspension modes and hunting modes. The results indicate that when the modal frequency of one hunting mode approaches that of corresponding suspension mode, the damping ratio of the two modes exhibits abnormal variation, and the modal frequency curve veers or is slightly disturbed. In exploring the coupling characteristics of hunting modes and suspension modes, revealing the variation trends and similarity of modal shapes, polar diagrams of modal shapes are presented, and the correlation distance is calculated. Equivalent conicity exerts a substantial influence on the effect of modal coupling, influencing minimum damping ratio and modal shape similarity within the modal coupling zone. To ensure sufficient stability margin for metro vehicles, it is necessary to avoid excessively low equivalent conicity. Finally, the phenomenon of vibration response deterioration within the modal coupling zone is confirmed through both a simplified model and a full DOF model.
{"title":"Modal coupling characteristics of primary hunting in metro vehicles: Carbody suspension modes and hunting modes","authors":"Longfei Chen, Yong Wang, Huailong Shi","doi":"10.1177/09544097241266915","DOIUrl":"https://doi.org/10.1177/09544097241266915","url":null,"abstract":"Due to coupling with carbody suspension modes in railway vehicles, primary hunting can lead to significant low frequency swaying of the carbody, severely deteriorating ride quality. In order to address this issue, this paper conducts a detailed investigation into the coupling effect between suspension modes and hunting modes of metro vehicles. Initially, a simplified lateral dynamics model is established, and a continuous modal tracking method is adopted for track suspension modes and hunting modes. The results indicate that when the modal frequency of one hunting mode approaches that of corresponding suspension mode, the damping ratio of the two modes exhibits abnormal variation, and the modal frequency curve veers or is slightly disturbed. In exploring the coupling characteristics of hunting modes and suspension modes, revealing the variation trends and similarity of modal shapes, polar diagrams of modal shapes are presented, and the correlation distance is calculated. Equivalent conicity exerts a substantial influence on the effect of modal coupling, influencing minimum damping ratio and modal shape similarity within the modal coupling zone. To ensure sufficient stability margin for metro vehicles, it is necessary to avoid excessively low equivalent conicity. Finally, the phenomenon of vibration response deterioration within the modal coupling zone is confirmed through both a simplified model and a full DOF model.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"35 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141774417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-22DOI: 10.1177/09544097241266289
Andre Luis Oliveira de Melo, Sakdirat Kaewunruen, Mayorkinos Papaelias
With an emphasis on the combined degradation of railway track geometry and components, an improved numerical approach is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of unsupported sleepers (US) configuration on VLL under cyclic loadings, elasto-plastic behaviour, and different operational dynamic conditions. The nonlinear numerical models are performed adopting an explicit finite element (FE) package, and their results are validated by field data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, and by a power function factor, which innovatively extends the response of US on VLL over a long term. Results shows that at 3 million cycles (or 60 MGT) the worst configuration for 20-ton axle load is at 5 US with 5-mm gap (5,51%), whereas for 30 and 40-ton axle loads is at 5 US with 2-mm gap (1.23% and 0,89%, respectively). This indicates that the axle load affects considerably the VLL as expected, however, the US condition plays an important role to accelerate it. Based on this study, the acceptable configuration of US can be specified for a minimum effect on VLL (thresholds) and, therefore, supports the development of practical maintenance guidelines to prolong the railway track service life.
{"title":"Effect of unsupported sleepers on vertical levelling loss of heavy-haul railway track geometry under cyclic loadings","authors":"Andre Luis Oliveira de Melo, Sakdirat Kaewunruen, Mayorkinos Papaelias","doi":"10.1177/09544097241266289","DOIUrl":"https://doi.org/10.1177/09544097241266289","url":null,"abstract":"With an emphasis on the combined degradation of railway track geometry and components, an improved numerical approach is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of unsupported sleepers (US) configuration on VLL under cyclic loadings, elasto-plastic behaviour, and different operational dynamic conditions. The nonlinear numerical models are performed adopting an explicit finite element (FE) package, and their results are validated by field data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, and by a power function factor, which innovatively extends the response of US on VLL over a long term. Results shows that at 3 million cycles (or 60 MGT) the worst configuration for 20-ton axle load is at 5 US with 5-mm gap (5,51%), whereas for 30 and 40-ton axle loads is at 5 US with 2-mm gap (1.23% and 0,89%, respectively). This indicates that the axle load affects considerably the VLL as expected, however, the US condition plays an important role to accelerate it. Based on this study, the acceptable configuration of US can be specified for a minimum effect on VLL (thresholds) and, therefore, supports the development of practical maintenance guidelines to prolong the railway track service life.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"74 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141774419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-22DOI: 10.1177/09544097241250370
Aihua Zhu, Dongping Long, Cong Du, Jianwei Yang, Fan Zhang
This paper aims to investigate the influence of different speed at the end of the constant power section of the traction characteristic curve (TCC) on the vehicle dynamic performance and evaluate the TCC. A dynamics co-simulation model is developed in SIMPACK and MATLAB for dynamic analysis of the urban rail vehicle (URV) under different traction characteristics. Then it is used to investigate how acceleration distance and vehicle dynamic performance varies with the speed at the end of the constant power section of the TCC under different starting torques. Moreover, the entropy weight TOPSIS method which is widely used to solve the multi-objective decision-making problem is chosen to evaluate the traction characteristics based on various dynamic performance indexes over 25 test sections and acceleration distance. The results show that under traction conditions, the starting torque has effects on the lateral and vertical accelerations of car body, lateral and vertical wheel-rail contact forces, derailment coefficient and wheel unloading factor. The higher the torque, the greater the value of each index, that means the poorer the vehicle ride characteristics and running safety. For a given starting torque, the dynamic performance indexes increase with the increase of the speed at the end of the constant power section from 50 km/h to 80 km/h during the vehicle speed-up process. The maximum growth rate of the lateral and vertical accelerations of car body, lateral and vertical wheel-rail contact forces are 17%, 8%, 8% and 2%, respectively, when the speed at the end of the constant power section increases from 50 km/h to 80 km/h. Last, the comprehensive evaluation of traction characteristics using entropy-weight TOPSIS method reveals when the starting torque is 800 [Formula: see text], 1000 [Formula: see text], 1200 [Formula: see text] and 1400 [Formula: see text], the corresponding optimal speed at the end of the constant power section is 80 km/h, 80 km/h, 70 km/h and 50 km/h, respectively. The result of the study can provide theoretical support for traction characteristic design and traction control for URVs.
本文旨在研究牵引特性曲线（TCC）恒功率段末端不同速度对车辆动态性能的影响，并对 TCC 进行评估。本文使用 SIMPACK 和 MATLAB 开发了一个动力学协同仿真模型，用于对不同牵引特性下的城轨车辆（URV）进行动力学分析。然后，利用该模型研究了在不同启动扭矩下，加速距离和车辆动态性能如何随 TCC 恒功率段末端速度的变化而变化。此外，还选择了广泛用于解决多目标决策问题的熵权 TOPSIS 方法，根据 25 个测试路段和加速距离的各种动态性能指标对牵引特性进行评价。结果表明，在牵引条件下，起动转矩对车体横向和纵向加速度、车轮与钢轨的横向和纵向接触力、脱轨系数和车轮卸载系数都有影响。扭矩越大，各项指标值越大，即车辆行驶特性和运行安全性越差。对于给定的起始扭矩，在车辆加速过程中，随着恒定功率段末端速度从 50 km/h 提高到 80 km/h，动态性能指标也随之提高。当恒定动力段末端速度从 50 km/h 增加到 80 km/h 时，车身横向和纵向加速度、车轮与导轨的横向和纵向接触力的最大增长率分别为 17%、8%、8% 和 2%。最后，利用熵权 TOPSIS 法对牵引特性进行综合评价，发现当起始扭矩为 800[计算公式：见正文]、1000[计算公式：见正文]、1200[计算公式：见正文]和 1400[计算公式：见正文]时，相应的恒功率段末端最佳速度分别为 80 km/h、80 km/h、70 km/h 和 50 km/h。研究结果可为城市轻轨车辆的牵引特性设计和牵引控制提供理论支持。
{"title":"Research on the traction characteristic evaluation of urban rail vehicles based on entropy weight TOPSIS","authors":"Aihua Zhu, Dongping Long, Cong Du, Jianwei Yang, Fan Zhang","doi":"10.1177/09544097241250370","DOIUrl":"https://doi.org/10.1177/09544097241250370","url":null,"abstract":"This paper aims to investigate the influence of different speed at the end of the constant power section of the traction characteristic curve (TCC) on the vehicle dynamic performance and evaluate the TCC. A dynamics co-simulation model is developed in SIMPACK and MATLAB for dynamic analysis of the urban rail vehicle (URV) under different traction characteristics. Then it is used to investigate how acceleration distance and vehicle dynamic performance varies with the speed at the end of the constant power section of the TCC under different starting torques. Moreover, the entropy weight TOPSIS method which is widely used to solve the multi-objective decision-making problem is chosen to evaluate the traction characteristics based on various dynamic performance indexes over 25 test sections and acceleration distance. The results show that under traction conditions, the starting torque has effects on the lateral and vertical accelerations of car body, lateral and vertical wheel-rail contact forces, derailment coefficient and wheel unloading factor. The higher the torque, the greater the value of each index, that means the poorer the vehicle ride characteristics and running safety. For a given starting torque, the dynamic performance indexes increase with the increase of the speed at the end of the constant power section from 50 km/h to 80 km/h during the vehicle speed-up process. The maximum growth rate of the lateral and vertical accelerations of car body, lateral and vertical wheel-rail contact forces are 17%, 8%, 8% and 2%, respectively, when the speed at the end of the constant power section increases from 50 km/h to 80 km/h. Last, the comprehensive evaluation of traction characteristics using entropy-weight TOPSIS method reveals when the starting torque is 800 [Formula: see text], 1000 [Formula: see text], 1200 [Formula: see text] and 1400 [Formula: see text], the corresponding optimal speed at the end of the constant power section is 80 km/h, 80 km/h, 70 km/h and 50 km/h, respectively. The result of the study can provide theoretical support for traction characteristic design and traction control for URVs.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"39 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141774420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-20DOI: 10.1177/09544097241266873
Shuo Dou, Wenpeng Liu
Studies on wheel flatness and polygonal wear have demonstrated that wheel defects cause severe impact forces at the wheel–rail interfaces. This study investigated the dynamic contact mechanical behaviour of high–speed train transmission gears when subjected to wheel defects. First, a train-track coupling dynamics model was established, considering the localized contact characteristics of transmission gears. This model was developed using the slice method and the Hertz contact model, exploring the spatial coupling effects between the gear contact interface and the train–track interface. Subsequently, the dynamic model was employed to extract essential contact mechanical parameters of the transmission gear under the influence of wheel defects, including gear meshing load, gear contact stress, and sliding velocity. Furthermore, an analysis was conducted to uncover and elucidate the mechanism by which wheel flatness and polygonal wear impact the dynamic contact behaviour of the transmission gear. This study underscores the importance of considering wheel defects when assessing the contact fatigue and wear performance of high-speed train transmission gears.
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Pub Date : 2024-06-22DOI: 10.1177/09544097241237836
Rahul Radhakrishnan, Moritz Schenker
SEnSOR (Smart Energy Speed Optimizer Rail) is a direct method based optimization algorithm developed at DLR for determining minimum energy speed trajectories for railway vehicles. This paper aims to reduce model error and improve this algorithm for any alternative powertrain architecture. Model simplifications such as projecting the efficiency maps of different train components onto one-dimensional space can lead to inaccuracies and non-optimalities in reality. In this work, 2D section-wise Chua functional representation was used to capture the complete behavior of efficiency maps and discuss its benefits. For this purpose, a new smoothing method was developed. It was observed that there is an average of 6% error in the energy calculation when both, 1D and 2D, models are compared against each other. Previously, solving for different powertrain architectures was time consuming with the requirement of manual modifications to the optimization problem. With a modular approach, the algorithm was modified to flexibly adapt the problem formulation to automatically take into account any changes in powertrain architectures with minimum user input. The benefit is demonstrated by performing optimization on a bi-mode train with three different power sources as developed within the EU-project FCH2RAIL. The advanced algorithm is now capable to adapt to such complex architectures and provide feasible optimization results within a reasonable time.
{"title":"Optimization algorithm for minimizing railway energy consumption in hybrid powertrain architectures: A direct method approach using a novel two-dimensional efficiency map approximation","authors":"Rahul Radhakrishnan, Moritz Schenker","doi":"10.1177/09544097241237836","DOIUrl":"https://doi.org/10.1177/09544097241237836","url":null,"abstract":"SEnSOR (Smart Energy Speed Optimizer Rail) is a direct method based optimization algorithm developed at DLR for determining minimum energy speed trajectories for railway vehicles. This paper aims to reduce model error and improve this algorithm for any alternative powertrain architecture. Model simplifications such as projecting the efficiency maps of different train components onto one-dimensional space can lead to inaccuracies and non-optimalities in reality. In this work, 2D section-wise Chua functional representation was used to capture the complete behavior of efficiency maps and discuss its benefits. For this purpose, a new smoothing method was developed. It was observed that there is an average of 6% error in the energy calculation when both, 1D and 2D, models are compared against each other. Previously, solving for different powertrain architectures was time consuming with the requirement of manual modifications to the optimization problem. With a modular approach, the algorithm was modified to flexibly adapt the problem formulation to automatically take into account any changes in powertrain architectures with minimum user input. The benefit is demonstrated by performing optimization on a bi-mode train with three different power sources as developed within the EU-project FCH2RAIL. The advanced algorithm is now capable to adapt to such complex architectures and provide feasible optimization results within a reasonable time.","PeriodicalId":54567,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part F-Journal of Rail and Rapid Transit","volume":"81 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141505372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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