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Table of Content

    10 February 2019, Volume 30 Issue 03
    Lser Wide-band Hardening of Steel Rails and Corresponding Fatigue Wear Property
    YANG Zhixiang, WANG Aihua, XIONG Dahui, ZHANG Kun, LUO Xiaohua
    2019, 30(03):  254-260. 
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    Nowadays, online slack quenching technique was widely used for the hardening of steel rails, but the hardness of hardened layers was relatively low and was insufficient to meet the wear resistance demands of heavy-haul railways. Laser hardening process was carried out on U71Mn rail surfaces by utilizing rectangle laser beam size with three different widths. The critical laser powers and hardened layer depths at different scanning velocities were obtained for the three different laser beam sizes. Furthermore, the wear and rolling contact fatigue property of laser-hardened layers were also investigated. Results show that under the same critical laser powers, the increase of laser beam widths from 6 mm to 20 mm results in a significant increase in hardened depths(about 38%) or productivity (about 6.8 times); the microstructures of the laser-hardened layers are composed of acicular martensite and have a much higher microhardness of 800HV in comparison with that of the original steel rails(about 300HV); the weight losses of laser-hardened specimens are only 25% of the untreated ones after 200 thousand cycle RCF tests; the damaged surfaces display severe contact fatigue spalling and plastic deformations for the untreated specimens but only slight fatigue wear for the laser-hardened specimens, which indicate the outstanding wear and RCF resistances for the laser-hardened rails.
    Influences of Rail Grinding Deviations on Vehicle Dynamics Performances of High Speed Railways
    CHI Maoru, CAI Wubin, LIANG Shulin, LI Yixiao, SUN Jianfeng, JIN Xuesong, HE Xiang
    2019, 30(03):  261-265,283. 
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    Aiming at two typical rail grinding deviations existed in China's high speed railways, a multi-body dynamics model of a China's certain type of electric multiple units(EMU) vehicle was established. The influences of the rail shoulder overgrinding and the rail head overgrinding on the wheel-rail matching relationships, the vehicle's hunting stabilities and running performances were analyzed. The simulations suggest that the positions of the contact points will be biased toward the outer ends of the treads and rail heads when rail shoulder overgrinding, which will lead to a low-conicity wheel-rail contact. Consequently, the so-called carbody hunting instability arises, and the carbody lateral acceleration increases and the sperling index deteriorates at the speed ranges where the bogie hunting motion excites. By contrast, in the case of rail head overgrinding, wheel rail contact points trend to be concentrated on the root parts of the tread throat and the rail shoulder, the so-called bogie hunting instability will be induced due to the extremely high-conicity wheel-rail contacts and the EMU frame lateral acceleration is forced to “alarm”. Thus, in order to improve the hunting stability and operation quality of the high speed trains, the grinding accuracy should be strictly controlled and the standard profiles should be the target profiles.
    A Robust Rail Surface Defect Detection Algorithm
    PENG Fangjin
    2019, 30(03):  266-270. 
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    When machine vision technology was used to detect the surface defects of rails, the background lighting was complex, the relative position of the on-board detection equipment and the rail changes, etc., which seriously affected the defect detection accuracy. Therefore, a rail surface area localization algorithm was proposed based on gray standard deviation and projection integration, and an enhancement algorithm was also presented based on multi-scale gray-scale contrasts. The gray standard deviation was used to eliminate the interferences of complex backgrounds, and the precise positions of the orbital surfaces was obtained through the projection integral, then, the gray-scale contrasts in different scale spaces were obtained to convert the rail surface areas into a gray contrast maps for defect enhancements, finally, iterative threshold segmentation method was used to extract rail surface defects. Experiments show that, under several different shooting conditions, the missing detection rate of the rail surface defect detection algorithm proposed is less than 6%, and the accuracy rate is more than 93%. This algorithm has high robustness for the detection of surface defects on seamless rails in high-speed ballast tracks.
    Safety Assessments of Rails with Crack Defects Based on SINTAP-FAD Method 
    YU Hui, , ZOU Haibei, LI Wei, ZHAI Jianwei, LIU Ligang,
    2019, 30(03):  271-278. 
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    In order to study the critical conditions of crack growth with different scales under different worked conditions, mechanics parameters and fracture mechanics parameters needed in safety assessment processes were obtained by experiments. Interaction integral method was adopted to calculate the stress intensity factors of crack tips on the rails with surface crack defects in the wheel-rail contacts, and the reference stresses were obtained by calculated effective net section stresses. According to 0 level of failure assessment curves, SINTAP-FAD method was adopted to evaluate the safety of rails with surface crack defects under the conditions of wheel stationary states and moving states respectively. The results show that the train speed has a great influence on the surface crack state of the rails. Compared with the situations that the evaluation points located in the safety zone when wheels are in stationary states, the evaluation points develop towards the unsafety zone under the conditions of moving states and result in crack propagation.
    Effects of Defect Morphologies on Rolling Contact Fatigue Characteristics of Wheel Materials
    ZHAO Xiangji, SHI Lubing, WANG Wenjian, GUO Jun, LIU Qiyue
    2019, 30(03):  278-283. 
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    The various defect morphologies were impacted on wheel rollers by pendulum machine. The rolling contact fatigue damage characteristics of the normal and two kinds of defected wheel materials were investigated using an improved MMS-2A rolling-sliding wear testing machine. The residual stress distributions on wheel materials after impacting were simulated by ABAQUS, and the crack initiations and propagating mechanism were discussed. The results indicate that the residual tensile stress vertical to the wheel tread emerges on subsurface materials, contributes to the crack initiation and growth compared with the normal wheels. The length and angle of cracks around ball defects are both larger than that around ballast defects under the same impact energy conditions. Moreover, the crack surfaces of the subsurface cracks at the edge of the around ball defects are wider and extend internally along the 45° expansion angle.
    Research Progresses and Prospect of Rail Grinding Mechanism
    ZHOU Kun, WANG Wenjian, LIU Qiyue, GUO Jun
    2019, 30(03):  284-294. 
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    The papar reviewed the material removal mechanism including material removal model and temperature field. After that, the removal behaviours under different grinding parameters, grinding stones and grinding conditions were introduced, respectively. Besides, the interaction mechanism between grinding efficiency and quality was put forward. Moreover, the influences of rail grinding on the wheel/rail rolling contact fatigue were concluded. It is suggested that the researches of the properties of grinding stones, such as abrasive composition, binder, granularity, hardness and blowhole, should be conducted to develop suitable grinding stones for China. This may reduce the grinding costs, and improve the grinding efficiency and quality. Moreover, it is necessary to further conduct experimental researches under special conditions. It is noteworthy that rail grinding should be combined with other railway maintenances to improve the rail service life and ensure a good wheel/rail contact conditions.
    Research on Fast Stretching Algorithm for Linear BIM Model of High-speed Railways
    LIU Ao
    2019, 30(03):  295-299. 
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    Aiming at the problems that were difficult for BIM software to stretch the solid quickly in the modeling processes at present, a fast stretching algorithm was proposed in BIM software, which including the 2D plane curve discretizated to three-dimensional space curve algorithm and the plane space transformation geometry algorithm. A specific BIM model stretching tool for high-speed railway projects was developed to realize the fast stretching of linear BIM model for high-speed railways, and the interval 3D design was carried out in the actual high-speed railway projects based on the proposed algorithm. The linear BIM model of high-speed railway was established quickly, and the design efficiency is improved by 100%.
    Design and Analysis of a New Kind of Railway Track Detection Trolley
    FU Wenlong, WANG Peijun, LI Wentao, ZHENG Xiaojiang, CHEN Yadong
    2019, 30(03):  300-305. 
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    Aiming at the current situations of low efficiency of manual track detection, single detection items and low penetration rate of high-speed track detection vehicles, a collapsible lightweight semi-T-shaped detection vehicle was designed to meet the requirements of optical vision detection, which could meet the requirements of laser detection and three-dimensional structural light detection. To solve the common problems that were difficult to guarantee the verticality between the track detection trolley frame and the rail longitudinal direction, a flexible side pressure mechanism was designed, which was mounted on the track detection trolley to prevent the frame deviation. Then, the D-H method was used to construct a kinematics model for solving the forward kinematics problems of the side pressure wheel at the end of the mechanism, and proved that side pressure wheel of flexible side pressure mechanism could contact tightly with inner side of rail to adapt the changes of the gauge. In order to ensure that the trolley would not roll over and derail in the static states, the mechanics analysis model of the trolley was established to verify the rationality of mechanism design. Finally, the physical prototype of the detection trolley was made and tested at the railway sites. Field tests show that the detection trolley has good verticality and self-adjusting ability to meet the inspection requirements.
    Developments and Applications of Intelligent Design Systems for Comprehensive Maintenance Facility Processes of High Speed Railways
    ZHAO Tiezhu, CUI Wanli, MENG Qingyu, CHEN Rongshun, WANG Xiaocen, XU Yong
    2019, 30(03):  306-309. 
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    The intelligent layout technologies based on geographic information system(GIS) and the whole process digital design technologies were researched, which formed the data standards of process design for high-speed railway comprehensive maintenance facilities. The intelligent design systems for comprehensive maintenance facility processes of high speed railways were developed,which realized the visualization of the maintenance facility layout plans, the intelligent outputs of the whole process design files and the parameterized drive of the complete set of drawings. Compared with the traditional layout technologies, the design efficiency and design standardization of the systems are improved greatly.
    Research on Circuit Breaker Virtual Assembly Systems Based on Time Petri Net
    YANG Yanfang, HE Huan, SHU Liang, YANG Miao, CHEN Ping, WU Ziran
    2019, 30(03):  310-317,324. 
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    An automatic virtual assembly system of circuit breakers was proposed based on time Petri net model herein. The behavior logic of assembly systems was described by the time-constrained nested Petri net model. To incorporate the Petri model into virtual simulation, the repositories and transition in the established Petri net model were related to the entity objects in the Unity 3D virtual scene. The method of time series drive was used to reconstruct the automatic assembly entity systems of circuit breakers in Unity 3D. The data exchange engines of virtual assembly systems were developed based on C# function library. Wi-Fi and industrial serial port might be used to exchange data with external entities. To implement the collision detection in the simulation, the bounding box detection method was used in the virtual assembly units and the spare parts. The virtual simulation was realized with Unity 3D and the feasibility and effectiveness of the systems were verified by simulations and demonstrations.
    Analysis of Vibration Characteristics of Low-medium Speed Maglev Levitation Systems in Lifting Stages
    LU Haiying, HAN Xiaohan, LI Zhongji, HE Xiang, LIU Kaicheng, CHEN Zhixian
    2019, 30(03):  318-324. 
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    In order to study the suspension stability of EMS low-medium spead maglev levitation in the lifting stages, the coupling dynamics models of “vehicle-electromagnetism-track beam” were established. The vibration response characteristics of EMS low-medium speed maglev systems were analyzed by using the simulation models, and the vibration differences between the elastic beam and rigid beam were compared. The differences between single-stage suspension control and two-stage suspension control were simulated. The results show that the lifting stages of the maglev trains are more prone to suspension instability on the elastic beams, maglev train abnormal vibrations are easy to occur; The reasons are that the self-excited vibration frequencies of suspension frames motivate the natural frequencies of elastic track beams, which induces the strong coupling resonance of the train tracks. Increasing the stiffness of track beams or adopting the two-stage suspension controller model may alleviate the abnormal vibrations of the suspension instability during EMS low-medium speed maglev levitation in the lifting stages.
    Precision Shaping Process and Method of Rail Welded Joints
    LUO Xiaohua, ZHANG Hao, ZHOU Peng
    2019, 30(03):  325-329. 
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    The principles and method of finish-milling process for rail weld seams were presented herein where the milling was used to instead of grinding, and the rail weld seams finish-milling machine were designed. The finish-milling machine might realize the non-contact high-precision measurements of the rail profiles, the automatic planning of the milling paths, the automatic control of the milling quantity and the online monitoring of the processing qualities, etc.. The damages of rail crystal structures and secondary deformations of welded joints caused by high temperature rises in traditional grinding were eliminated and the production efficiency and the quality of seamless rails were improved. This finish-milling machine is superior to imported refiners in welding precision, efficiency and environmental protection.
    Research on MF Inverter DC Rail Welding Technology
    ZHANG Yinlong, ZHANG Kun, WANG Xuehua, ZHANG Baojun
    2019, 30(03):  330-333. 
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    The development of high-speed rail welding equipment at home and abroad was analyzed herein. The characteristics and advantages of MF inverter DC welding technology were summarized, and the mechanical structures, inverter transformers and control systems of the self-developed MF inverter DC welding machine and the product tests were introduced. The results show that the MF inverter DC welding machine developed by the project has the characteristics of dense welding currents, no obvious skin effects and high drop rates. The relevant performances are the same as that of abroad advanced levels, which have important reference significances for the welding of high-speed rail seamless rails.
    Design of Long Rail Handling Systems Based on Gray Bus
    YOU Penghui
    2019, 30(03):  334-338,344. 
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    In order to improve the efficiency of handling 100 m long rails and to reduce the bending and torsional deformations of rails, a long rail handling system was designed. The precision address detection was carried out by using Gray bus line positioning technology. The fieldbus technology was used for remote centralized control to solve the problems of shifting rails out of synchronization. Rail induction sensors and contact switches were installed to search the rails automatically. The operation interfaces were designed to control the operation processes of single and multiple rails and to show the states and faults of the shifting rail trolleys. The research results show that the positioning accuracy of the system may reach 5 mm, which realizes high precision synchronous translations of long rails.
    High-speed Railway Rail Ultrasound Flaw Detection Systems Based on Phased Array
    ZHANG Junling, WANG Zicheng, CHEN Xiao, SUN Ji, HAN Zhixiong, MIN li, YU Guolong, GENG Ming
    2019, 30(03):  339-344. 
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    In view of the low reliability, high false alarm rate and hidden troubles of the existing auto-flaw detection equipment, which was difficult to meet the needs of the development and construction planning of high-speed railway engineering technology, a new type of rail ultrasonic flaw detection system was proposed. A high-speed recording multi-channel digital flaw detector was developed for real-time acquisition of full waveform data under high-speed rail detection conditions, and the phased array ultrasonic system was used to detect rail welded joints. The effectiveness of the system was verified by experiments.The research results show that the system may collect flaw detection data in high-speed, realize flaw detection, record and intelligent data analysis in real-time.
    Researches and Applications of Control Method for Flatness of High Speed Rail Ends
    HE Wenji, DONG Maosong, XU Sen, WANG Yongyuan
    2019, 30(03):  345-348. 
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    To solve the problems of substandard rail end flatness, the reasons for the unqualified flatness were analyzed, the impact forces of the rails in each pass mill and the tendency of tapping were inconsistent that resulted in different original curvature sizes and directions thus the instable flatness was produced after straightening. In order to solve the problem of unstable end flatness, the orthogonal experiments were designed using the large deformation + small deformation straightening, and the optimal straightening pressure parameters were obtained. The original curvature control ranges were obtained by analyzing the flatness data before and after corrections. Through the above measures, the end flatness of the rails after the optimized straightening processes fully meets the standard within a small fluctuation ranges.
    Condition Monitoring and Preventive Maintenance of Ballastless Track Systems for High-speed Railways
    LIU Daling, HUANG Xiaogang
    2019, 30(03):  349-353. 
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    The ballastless track systems of high-speed railways directly beared the high-frequency impacts and vibrations of high-speed trains, and the state changes of rail stretch deformation seriously affected trained safety. Traditional periodic maintenances were prone to overhaul or disrepair. A condition monitoring platform for ballastless track systems of high-speed railways was established by using fiber Bragg grating sensing technology, and the monitoring contents and monitoring point layout schemes were proposed. By analyzing the basic characteristics of monitoring data and combining with the track quality index, a back propagation(BP) neural network prediction model for ballastless track states was established, which was used to predict the service stats of rails. Prediction results guide the operation and maintenance departments to carry out timely and reasonable track maintenance and maintenance, so as to achieve preventive maintenance of high-speed rail systems.
    Study on Rapid Rail-changing Vehicles of High-speed Railways by Self-wheeling Operation
    LEI Zhangwen, NI Li, LI Shiping, FANG Jiwu
    2019, 30(03):  354-358. 
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    In order to realize replacements of railroad tracks for the high-speed railways automatic ally, the principles of rail-changing operations and key technologies were studied,which targeted on the rapid rail-changing vehicles of high-speed railways by self-wheeling operation . And the performances of the railcar were verified through the application tests of the rapid rail-changing vehicles by self-wheeling operation. The research results show that, compared with the traditional rail changing operations using simple implements or modified vehicles, the rapid rail-changing vehicles by self-wheeling operation may save the “sky-light” time about 20 minutes under the 2 km operation volume, and the maximum daily rail change mileages may reach 2.4 km. This new vehicle is more efficient, safer and low operating intensity.
    Design of Tamping, Stabilization, Measurement Integrated Simulation Vehicles by Using Finite Element Method
    LI Chengyang
    2019, 30(03):  359-364. 
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    The emergency recovery simulation vehicles integrated tamping, stabilization and measurement devices were developed by finite element analysis. Through the analyses under ten working conditions, the rigidity and strength of the car bodys may meet the requirements and the load distributions are reasonable. During the development processes some technical challenges such as whole machine layout, multiple working devices sharing the one car body, repeated derailment and recovery were solved. The simulation vehicles might provide training for rail and infrastructure maintenances, as well as fault simulation of emergency repairs for the large-scale track maintenance machines and functional simulation of rapid off-track and recovery, which might train rail maintenance and emergency rescue personnels economically, effectively with high quality. It is ensured that the whole processes of entry, construction and evacuation of large-scale track maintenance machines are completed within the “skylight” blockade time when the line is busy.
    Development of Dual-power 48 Grinding Stone Rail Grinding Trains
    YANG Jianchang, WANG Jianhong, ZHU Hongjun, XIANG Penglin, HUANG Gan, ZHOU Mingxiang
    2019, 30(03):  365-371. 
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    Three technical implementation routes of the dual-power 48 grinding stone rail grinding trains were analyzed, and the technical route of the trains adopted by “diesel generator set + overhead contact system + AC drive” was determined, then the key technologies of the trains were listed. The main structures and performances of the trains were introduced, and the traction characteristics were calculated and analyzed under the self-running conditions and grinding working conditions respectively. Finally, the railway adaptability, product advantages, social benefits and test conditions of the trains were described. The calculation analysis and test results show that the traction characteristics of dual-power 48 grinding stone rail grinding trains meet the working requirements on long steep grades, and the trains adapt to the existing passenger line of various speed grades, the strength of car bodys and bogies, the dynamics performance and the working performances all meet the requirements of test standards. The trains also have the advantages of energy saving and environmental protection, and are suitable for tunnel grinding.
    Development of Emergency Rescue Simulation Training Systems for Large-scale Track Maintenance Machines
    LIU Hui
    2019, 30(03):  372-377. 
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    Considering the lack of emergency rescue mode of large-scale track maintenance machines, the shortages of professional and the diseconomy of using operating vehicles, an emergency repair simulation training platform system was designed, which was used to simulate various vehicle conditions. The emergency rescue conditions and characteristics were analyzed under actual environmental systems, and then a virtual simulation environment was constructed by system simulation, virtual reality, distributed network and other technologies. Through the simulations, the real experience might be obtained. It is an effective and economic method for people to be trained in destructive, dangerous conditions, or special status and other restrict environments, and effectively culticating professional emergency rescue personnels with fast response and high quality, so that personnels may master the emergency rescue technology skillfully.