To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wh...To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting process.The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail.In each rotation,the casting wheel passes through four different spray zones.The results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,respectively.The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.展开更多
In order to analyze the characteristics of wheel-rail vibration of the vertical section in a high-speed railway, a vehicle-line dynamics model is established using the dynamics software SIMPACK. Through this model, th...In order to analyze the characteristics of wheel-rail vibration of the vertical section in a high-speed railway, a vehicle-line dynamics model is established using the dynamics software SIMPACK. Through this model, the paper analyzes the influence of vertical section parameters, including vertical section slope and vertical curve radius, on wheel-rail dynamics interaction and the acting region of wheel-rail vibration. In addition, the characteristics of wheel- rail vibration of the vertical section under different velocities are investigated. The results show that the variation of wheel load is not sensitive to the vertical section slope but is greatly affected by the vertical curve radius. It was also observed that the smaller the vertical curve radius is, the more severe the interaction between the wheel and rail be- comes. Furthermore, the acting region of wheel-rail vibration expands with the vertical curve radius increasing. On another note, it is necessary to match the slope and vertical curve radius reasonably, on account of the influence of operation speed on the characteristics of wheel-rail vibration. This is especially important at the design stage of vertical sec- tions for lines of different grades.展开更多
A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the...A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.展开更多
This paper studies the title problem including an analysis of the gyroscopic effects of the wheels of a rail-car travelling at high-speed around a level, horizontal curve. The analysis is based upon the fundamental pr...This paper studies the title problem including an analysis of the gyroscopic effects of the wheels of a rail-car travelling at high-speed around a level, horizontal curve. The analysis is based upon the fundamental principles of dynamics. The result is a design formula for the minimum curve radius needed to prevent derailment. Aside from the rail car geometric and physical properties, the minimum curve radius depends upon the square the train speed. An illustrative example shows that the wheel gyroscopic effect is destabilizing and additive to the centrifugal force derailment tendency. From a track design perspective, however, the gyroscopic effect is relatively small compared with the centrifugal force effect.展开更多
A three-dimensional (3-D) wheel-rail rolling contact model with a wheel fiat was built using commercial software Hypermesh, and the dynamic finite element simulation was conducted using LS-DYNA 3D/explicit code. Inf...A three-dimensional (3-D) wheel-rail rolling contact model with a wheel fiat was built using commercial software Hypermesh, and the dynamic finite element simulation was conducted using LS-DYNA 3D/explicit code. Influences of the train speed, flat length and axle load on the vertical wheel-rail impact response were discussed, respectively. The results show that the maximum vertical wheel-rail impact force induced by the wheel flat is higher than that generated by the perfect wheel, and these two dynamic impact forces are much greater than the static axle load. Besides, the maximum von Mises equivalent stress and maximum equivalent plastic strain are observed on the wheel-rail contact surface, and both of them as well as the maximum wheel-rail impact force are sensitive to train speed, fiat length and axle load.展开更多
This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspens...This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspension system. Based on the new nonlinear creep model derived from combining Hertz contact theory, Kalker's linear theory and a heuristic nonlinear creep model, the modeling and dynamic analysis of a 24 degree-of-freedom railway vehicle system were investigated. The Lyapunov indirect method was used to examine the effects of suspension parameters, wheel conicities and wheel rolling radii on critical hunting speeds. Generally, the critical hunting speeds of a vehicle system resulting from worn wheels with different wheel rolling radii are lower than those of a vehicle system having original wheels without different wheel rolling radii. Because of worn wheels, the critical hunting speed of a running railway vehicle substantially declines over the long term. For safety reasons, it is necessary to design the suspension system parameters to increase the robustness of the system and decrease the sensitive of wheel noises. By applying UD and QPSO, the nominal-the-best signal-to-noise ratio of the system was increased from -48.17 to -34.05 dB. The rate of improvement was 29.31%. This study has demonstrated that the integration of UD and QPSO can successfully reveal the optimal solution of suspension parameters for solving the robust design problem of a railway vehicle suspension system.展开更多
The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. Ho...The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.展开更多
Purpose–In service,the periodic clashes of wheel flat against the rail result in large wheel/rail impact force and high-frequency vibration,leading to severe damage on the wheelset,rail and track structure.This study...Purpose–In service,the periodic clashes of wheel flat against the rail result in large wheel/rail impact force and high-frequency vibration,leading to severe damage on the wheelset,rail and track structure.This study aims to analyze characteristics and dynamic impact law of wheel and rail caused by wheel flat of high-speed trains.Design/methodology/approach–A full-scale high-speed wheel/rail interface test rig was used for the test of the dynamic impact of wheel/rail caused by wheel flat of high-speed train.With wheel flats of different lengths,widths and depths manually set around the rolling circle of the wheel tread,and wheel/rail dynamic impact tests to the flats in the speed range of 0–400 km/h on the rig were conducted.Findings–As the speed goes up,the flat induced the maximum of the wheel/rail dynamic impact force increases rapidly before it reaches its limit at the speed of around 35 km/h.It then goes down gradually as the speed continues to grow.The impact of flat wheel on rail leads to 100–500 Hz middle-frequency vibration,and around 2,000 Hz and 6,000 Hz high-frequency vibration.In case of any wheel flat found during operation,the train speed shall be controlled according to the status of the flat and avoid the running speed of 20 km/h–80 km/h as much as possible.Originality/value–The research can provide a new method to obtain the dynamic impact of wheel/rail caused by wheel flat by a full-scale high-speed wheel/rail interface test rig.The relations among the flat size,the running speed and the dynamic impact are hopefully of reference to the building of speed limits for HSR wheel flat of different degrees.展开更多
Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stabil...Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stability and passenger safety.Since wheel/rail contact forces of high-speed train are very difficult to measure directly,a new estimation process for wheel/rail contact forces was introduced in this work.Based on the state space equation,dynamic programming methods and the Bellman principle of optimality,the main theoretical derivation of the inversion mathematical model was given.The new method overcomes the weakness of large fluctuations which exist in current inverse techniques.High-speed vehicle was chosen as the research object,accelerations of axle box as input conditions,10 degrees of freedom vertical vibration model and 17 degrees of freedom lateral vibration model were established,respectively.Under 250 km/h,the vertical and lateral wheel/rail forces were identified.From the time domain and frequency domain,the comparison of the results between inverse and SIMPACK models were given.The results show that the inverse mathematical model has high precision for inversing the wheel/rail contact forces of an operation high-speed vehicle.展开更多
Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with meri...Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with merits and defects of each approach stated. Through simulations, the Kalman filter method based on minimum wheel speed shows improved accuracy, in addition to better adaptivity to vehicle reference speed. It also can be used to acceleration ship regulation (ASR) in part-time four-wheel drive vehicles.展开更多
Purpose–The purpose of this paper is to summarize the status and characteristics of rail technology of high-speed railway in China,and point out the development direction of rail technology of high-speed railway.Desi...Purpose–The purpose of this paper is to summarize the status and characteristics of rail technology of high-speed railway in China,and point out the development direction of rail technology of high-speed railway.Design/methodology/approach–This study reviews the evolution of high-speed rail standards in China,comparing their chemical composition,mechanical attributes and geometric specifications with EN standards.It delves into the status of rail production technology,shifts in key performance indicators and the quality characteristics of rails.The analysis further examines the interplay between wheels and rails,the implementation of grinding technology and the techniques for inspecting rail service conditions.It encapsulates the salient features of rail operation and maintenance within the high-speed railway ecosystem.The paper concludes with an insightful prognosis of high-speed railway technology development in China.Findings–The rail standards of high-speed railway in China are scientific and advanced,highly operational and in line with international standards.The quality and performance of rail in China have reached the world’s advanced level.The 60N profile guarantees the operation quality of wheel–rail interaction effectively.The rail grinding technology system scientifically guarantees the long-term good service performance of the rail.The rail service state detection technology is scientific and efficient.The rail technology will take“more intelligent”and“higher speed”as the development direction to meet the future needs of high-speed railway in China.Originality/value–The development direction of rail technology for high-speed railway in China is defined,which will promote the continuous innovation and breakthrough of rail technology.展开更多
The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recover...The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.展开更多
Wheel/rail relationship is a fundamental problem of railway system. Wear of wheel profiles has great effect on vehicle performance. Thus, it is important not just for the analysis of wear characteristics but for its p...Wheel/rail relationship is a fundamental problem of railway system. Wear of wheel profiles has great effect on vehicle performance. Thus, it is important not just for the analysis of wear characteristics but for its prediction. Actual wheel profiles of the high-speed trains on service were measured in the high-speed line and the wear characteristics were analyzed which came to the following results. The wear location was centralized from-15 mm to 25 mm. The maximum wear value appeared at the area of 5 mm from tread center far from wheel flange and it was less than 1.5 mm. Then, wheel wear was fitted to get the polynomial functions on different locations and operation mileages. A binary numerical prediction model was raised to predict wheel wear. The prediction model was proved by vehicle system dynamics and wheel/rail contact geometry. The results show that the prediction model can reflect wear characteristics of measured profiles and vehicle performances.展开更多
Purpose–In order to systematically grasp the changes and matching characteristics of wheel and rail profiles of high speed railway(HSR)in China,172 rail profile measurement points and 384 wheels of 6 high-speed elect...Purpose–In order to systematically grasp the changes and matching characteristics of wheel and rail profiles of high speed railway(HSR)in China,172 rail profile measurement points and 384 wheels of 6 high-speed electric motive unites(EMUs)were selected on 6 typical HSR lines,including Beijing–Shanghai,Wuhan–Guangzhou,Harbin–Dalian,Lanzhou–Xinjiang,Guiyang–Guangzhou and Dandong–Dalian for a two-year field test.Design/methodology/approach–Based on the measured data,the characteristics of rail and wheel wear were analyzed by mathematical statistics method.The equivalent conicity of wheel and rail matching in a wheel reprofiling cycle was analyzed by using the measured rail profile.Findings–Results showed that when the curve radius of HSR was larger than 2,495 m,the wear rate of straight line and curve rail was almost the same.For the line with annual traffic gross weight less than 11 Mt,the vertical wear of rail was less than 0.01 mm.The wear rate of the rail with the curve radius less than 800 m increased obviously.The wheel tread wear of EMUs on Harbin–Dalian line,Lanzhou–Xinjiang line and Dandong–Dalian line was relatively large,and the average wear rate of tread was about 0.05–0.06 mm$(10,000 km)1,while that of Beijing–Shanghai line,Wuhan–Guangzhou line and Guiyang–Guangzhou line was about 0.03–0.035 mm$(10,000 km)1.When the wear range was small,the equivalent conicity increased with the increase of wheel tread wear.When the wear range of wheel was wide,the wheel–rail contact points were evenly distributed,and the equivalent conicity did not increase obviously.Originality/value–This research proposes the distribution range of the equivalent conicity in one reprofiling cycle of various EMU trains,which provides guidance for the condition-based wheel reprofiling.展开更多
In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the ac...In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the actual measured track irregularities and line conditions were considered. The wear depth of the wheel profile was calculated by the well-known Archard wear law. Through this model, the influence of the wheel profile, primary suspension stiffness, track gage, and rail cant on the wear of wheel profile were studied through multiple iterafive calculations. Numerical simulation results show that the type XP55 wheel profile has the smallest cumulative wear depth, and the type LM wheel profile has the largest wear depth. To reduce the wear of the wheel profile, the equivalent conicity of the wheel should not be too large or too small. On the other hand, a small primary vertical stiffness, a track gage around 1,435-1,438 mm, and a rail cant around 1:35-1:40 are beneficial for dynamic performance improvement and wheel wear alleviation.展开更多
The fexibility of a train's wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel...The fexibility of a train's wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel web,a specifi coupling of wheel–rail contact with a fexible wheelset is presented and integrated into a conventional vehicle–track dynamic system model.Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelset bending and axial deformation of the wheel web on wheel–rail rolling contact behaviors.Excitations with various irregularities and speeds were considered.The irregularities included measured track irregularity and harmonic irregularities with two different wavelengths.The speeds ranged from 200 to400km/h.The results show that the proposed model can characterize the effects of fexible wheelset deformation on the wheel–rail rolling contact behavior very well.展开更多
This paper posits that a low-speed wind turbine design is suitable for harnessing wind energy in Africa.Conventional wind turbines consisting of propeller designs are commonly used across the world.A major hurdle to u...This paper posits that a low-speed wind turbine design is suitable for harnessing wind energy in Africa.Conventional wind turbines consisting of propeller designs are commonly used across the world.A major hurdle to utilizing wind energy in Africa is that conventional commercial wind turbines are designed to operate at wind speeds greater than those prevalent in most of the continent,especially in sub-Sahara Africa(SSA).They are heavy and expensive to purchase,install,and maintain.As a result,only a few countries in Africa have been able to include wind energy in their energy mix.In this paper,the feasibility of a novel low-speed wind turbine based on a Ferris wheel is demonstrated for low wind speed applications in Africa.The performance of Ferris wheel wind turbines(FWT)with 61m(200 ft),73m(240 ft)and 104m(341 ft)diameter rims and an 800kW generator are evaluated for selected African cities.The research also compares the Weibull wind distribution of the African cities of interest.A comparison between the FWT and the conventional commercial wind turbines in terms of efficiency,rated wind speed,cost,performance,and power to weight is included.Results show that the FWT has the potential for economic power generation at rated wind speeds of 6.74m/s,which are lower than the average of 12 m/s for conventional wind turbines and have lower power to weight ratios of 5.2 kW/tonne as compared to 6.0-9.2 kW/tonne for conventional wind turbines.展开更多
A new method for ergonomic design of a computer mouse is proposed in this paper. In the method, the movements of joints and tip of the forefinger during operating a mouse was captured by a high-speed video camera. The...A new method for ergonomic design of a computer mouse is proposed in this paper. In the method, the movements of joints and tip of the forefinger during operating a mouse was captured by a high-speed video camera. The captured videos were ana- lyzed and an algorithm was developed to decide the size and location of the mouse wheel according to ergonomic principles. The al- gorithm was then coded in a software package with Visual C++ and OpenGL languages. Results of the calculation and simulation agreed well with those of the experiments. The software can also be used for shape design of mouse body, buttons and their layouts.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.U20A20289)the Innovative Research Groups Project of the Natural Science Foundation of Hebei Province(Grant No.E2021203011)the Central Government Guides Local Science and Technology Development Fund Project(Grant No.206Z1601G)。
文摘To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting process.The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail.In each rotation,the casting wheel passes through four different spray zones.The results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,respectively.The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.
基金support and motivation provided by the National Natural Science Foundation of China (No. 51075340)the Fok YingTong Education Foundation for Young Teachers in the Higher Education Institutions of China (No. 121075)the Program for Innovation Research Team in University in China (No. IRT1178)
文摘In order to analyze the characteristics of wheel-rail vibration of the vertical section in a high-speed railway, a vehicle-line dynamics model is established using the dynamics software SIMPACK. Through this model, the paper analyzes the influence of vertical section parameters, including vertical section slope and vertical curve radius, on wheel-rail dynamics interaction and the acting region of wheel-rail vibration. In addition, the characteristics of wheel- rail vibration of the vertical section under different velocities are investigated. The results show that the variation of wheel load is not sensitive to the vertical section slope but is greatly affected by the vertical curve radius. It was also observed that the smaller the vertical curve radius is, the more severe the interaction between the wheel and rail be- comes. Furthermore, the acting region of wheel-rail vibration expands with the vertical curve radius increasing. On another note, it is necessary to match the slope and vertical curve radius reasonably, on account of the influence of operation speed on the characteristics of wheel-rail vibration. This is especially important at the design stage of vertical sec- tions for lines of different grades.
基金supported by the National Natural Science Foundation of China(No.51275429)
文摘A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.
文摘This paper studies the title problem including an analysis of the gyroscopic effects of the wheels of a rail-car travelling at high-speed around a level, horizontal curve. The analysis is based upon the fundamental principles of dynamics. The result is a design formula for the minimum curve radius needed to prevent derailment. Aside from the rail car geometric and physical properties, the minimum curve radius depends upon the square the train speed. An illustrative example shows that the wheel gyroscopic effect is destabilizing and additive to the centrifugal force derailment tendency. From a track design perspective, however, the gyroscopic effect is relatively small compared with the centrifugal force effect.
基金supported by the National Natural Science Foundation of China (Grant No. 51475392)the Fundamental Research Funds for the Central Universities (Grant No. 2682015RC09)the Research Fund of State Key Laboratory of Traction Power (Grant No. 2015TPL_T02)
文摘A three-dimensional (3-D) wheel-rail rolling contact model with a wheel fiat was built using commercial software Hypermesh, and the dynamic finite element simulation was conducted using LS-DYNA 3D/explicit code. Influences of the train speed, flat length and axle load on the vertical wheel-rail impact response were discussed, respectively. The results show that the maximum vertical wheel-rail impact force induced by the wheel flat is higher than that generated by the perfect wheel, and these two dynamic impact forces are much greater than the static axle load. Besides, the maximum von Mises equivalent stress and maximum equivalent plastic strain are observed on the wheel-rail contact surface, and both of them as well as the maximum wheel-rail impact force are sensitive to train speed, fiat length and axle load.
基金the Ministry of Science and Technology of Taiwan (Grants MOST 104-2221-E-327019, MOST 105-2221-E-327-014) for financial support of this study
文摘This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspension system. Based on the new nonlinear creep model derived from combining Hertz contact theory, Kalker's linear theory and a heuristic nonlinear creep model, the modeling and dynamic analysis of a 24 degree-of-freedom railway vehicle system were investigated. The Lyapunov indirect method was used to examine the effects of suspension parameters, wheel conicities and wheel rolling radii on critical hunting speeds. Generally, the critical hunting speeds of a vehicle system resulting from worn wheels with different wheel rolling radii are lower than those of a vehicle system having original wheels without different wheel rolling radii. Because of worn wheels, the critical hunting speed of a running railway vehicle substantially declines over the long term. For safety reasons, it is necessary to design the suspension system parameters to increase the robustness of the system and decrease the sensitive of wheel noises. By applying UD and QPSO, the nominal-the-best signal-to-noise ratio of the system was increased from -48.17 to -34.05 dB. The rate of improvement was 29.31%. This study has demonstrated that the integration of UD and QPSO can successfully reveal the optimal solution of suspension parameters for solving the robust design problem of a railway vehicle suspension system.
基金supported by National Natural Science Foundation of China (Grant Nos. 51175032, U1134201)National Basic Research Program of China (973 Program, Grant No. 2011CD711104)
文摘The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.
基金by CHINA RAILWAY Scientific and Technological Research and Development Project(contract no.2015J007-E and 2016J007-H)which the authors hereby express their appreciation.
文摘Purpose–In service,the periodic clashes of wheel flat against the rail result in large wheel/rail impact force and high-frequency vibration,leading to severe damage on the wheelset,rail and track structure.This study aims to analyze characteristics and dynamic impact law of wheel and rail caused by wheel flat of high-speed trains.Design/methodology/approach–A full-scale high-speed wheel/rail interface test rig was used for the test of the dynamic impact of wheel/rail caused by wheel flat of high-speed train.With wheel flats of different lengths,widths and depths manually set around the rolling circle of the wheel tread,and wheel/rail dynamic impact tests to the flats in the speed range of 0–400 km/h on the rig were conducted.Findings–As the speed goes up,the flat induced the maximum of the wheel/rail dynamic impact force increases rapidly before it reaches its limit at the speed of around 35 km/h.It then goes down gradually as the speed continues to grow.The impact of flat wheel on rail leads to 100–500 Hz middle-frequency vibration,and around 2,000 Hz and 6,000 Hz high-frequency vibration.In case of any wheel flat found during operation,the train speed shall be controlled according to the status of the flat and avoid the running speed of 20 km/h–80 km/h as much as possible.Originality/value–The research can provide a new method to obtain the dynamic impact of wheel/rail caused by wheel flat by a full-scale high-speed wheel/rail interface test rig.The relations among the flat size,the running speed and the dynamic impact are hopefully of reference to the building of speed limits for HSR wheel flat of different degrees.
基金Project(2009BAG12A04-A11)supported by the National Key Technology R&D Program in the"11-th Five-year Plan"of ChinaProjects(51275432,51005190)supported by the National Natural Science Foundation of ChinaProject(SWJTU09ZT23)supported by University Doctor Academics Particularly Science Research Fund,China
文摘Operation safety and stability of the train mainly depend on the interaction between the wheel and rail.Knowledge of wheel/rail contact force is important for vehicle control systems that aim to enhance vehicle stability and passenger safety.Since wheel/rail contact forces of high-speed train are very difficult to measure directly,a new estimation process for wheel/rail contact forces was introduced in this work.Based on the state space equation,dynamic programming methods and the Bellman principle of optimality,the main theoretical derivation of the inversion mathematical model was given.The new method overcomes the weakness of large fluctuations which exist in current inverse techniques.High-speed vehicle was chosen as the research object,accelerations of axle box as input conditions,10 degrees of freedom vertical vibration model and 17 degrees of freedom lateral vibration model were established,respectively.Under 250 km/h,the vertical and lateral wheel/rail forces were identified.From the time domain and frequency domain,the comparison of the results between inverse and SIMPACK models were given.The results show that the inverse mathematical model has high precision for inversing the wheel/rail contact forces of an operation high-speed vehicle.
文摘Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with merits and defects of each approach stated. Through simulations, the Kalman filter method based on minimum wheel speed shows improved accuracy, in addition to better adaptivity to vehicle reference speed. It also can be used to acceleration ship regulation (ASR) in part-time four-wheel drive vehicles.
基金supported by the National Key R&D Program of China[Grant No.2022YFB2603402]the Task of Science and Technology R&D Program of China Railway Corporation[Grant No.K2023G013]the R&D Fund Project of China Academy of Railway Science Corporation Limited[Grant No.2022YJ165].
文摘Purpose–The purpose of this paper is to summarize the status and characteristics of rail technology of high-speed railway in China,and point out the development direction of rail technology of high-speed railway.Design/methodology/approach–This study reviews the evolution of high-speed rail standards in China,comparing their chemical composition,mechanical attributes and geometric specifications with EN standards.It delves into the status of rail production technology,shifts in key performance indicators and the quality characteristics of rails.The analysis further examines the interplay between wheels and rails,the implementation of grinding technology and the techniques for inspecting rail service conditions.It encapsulates the salient features of rail operation and maintenance within the high-speed railway ecosystem.The paper concludes with an insightful prognosis of high-speed railway technology development in China.Findings–The rail standards of high-speed railway in China are scientific and advanced,highly operational and in line with international standards.The quality and performance of rail in China have reached the world’s advanced level.The 60N profile guarantees the operation quality of wheel–rail interaction effectively.The rail grinding technology system scientifically guarantees the long-term good service performance of the rail.The rail service state detection technology is scientific and efficient.The rail technology will take“more intelligent”and“higher speed”as the development direction to meet the future needs of high-speed railway in China.Originality/value–The development direction of rail technology for high-speed railway in China is defined,which will promote the continuous innovation and breakthrough of rail technology.
基金supported by the National Natural Science Foundation of China[grant number 41875105]the National Key R&D Program of China[grant number 2018YFA0606002]the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars[grant number BK20211540]。
基金supported by the National Natural Science Foundation of China(Grant 51305437)Guangdong Innovative Research Team Program of China(Grant201001D0104648280)
文摘The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.
基金Project(U1234208)supported by the Major Program of the National Natural Science Foundation of ChinaProject(2013J008-A)supported by the Research and Development Plan of Major Tasks in Science and Technology China Railways Co.Ltd.,China
文摘Wheel/rail relationship is a fundamental problem of railway system. Wear of wheel profiles has great effect on vehicle performance. Thus, it is important not just for the analysis of wear characteristics but for its prediction. Actual wheel profiles of the high-speed trains on service were measured in the high-speed line and the wear characteristics were analyzed which came to the following results. The wear location was centralized from-15 mm to 25 mm. The maximum wear value appeared at the area of 5 mm from tread center far from wheel flange and it was less than 1.5 mm. Then, wheel wear was fitted to get the polynomial functions on different locations and operation mileages. A binary numerical prediction model was raised to predict wheel wear. The prediction model was proved by vehicle system dynamics and wheel/rail contact geometry. The results show that the prediction model can reflect wear characteristics of measured profiles and vehicle performances.
基金supported by the China Academy of Railway Sciences Corporation Limited(Grant no.2019YJ162).
文摘Purpose–In order to systematically grasp the changes and matching characteristics of wheel and rail profiles of high speed railway(HSR)in China,172 rail profile measurement points and 384 wheels of 6 high-speed electric motive unites(EMUs)were selected on 6 typical HSR lines,including Beijing–Shanghai,Wuhan–Guangzhou,Harbin–Dalian,Lanzhou–Xinjiang,Guiyang–Guangzhou and Dandong–Dalian for a two-year field test.Design/methodology/approach–Based on the measured data,the characteristics of rail and wheel wear were analyzed by mathematical statistics method.The equivalent conicity of wheel and rail matching in a wheel reprofiling cycle was analyzed by using the measured rail profile.Findings–Results showed that when the curve radius of HSR was larger than 2,495 m,the wear rate of straight line and curve rail was almost the same.For the line with annual traffic gross weight less than 11 Mt,the vertical wear of rail was less than 0.01 mm.The wear rate of the rail with the curve radius less than 800 m increased obviously.The wheel tread wear of EMUs on Harbin–Dalian line,Lanzhou–Xinjiang line and Dandong–Dalian line was relatively large,and the average wear rate of tread was about 0.05–0.06 mm$(10,000 km)1,while that of Beijing–Shanghai line,Wuhan–Guangzhou line and Guiyang–Guangzhou line was about 0.03–0.035 mm$(10,000 km)1.When the wear range was small,the equivalent conicity increased with the increase of wheel tread wear.When the wear range of wheel was wide,the wheel–rail contact points were evenly distributed,and the equivalent conicity did not increase obviously.Originality/value–This research proposes the distribution range of the equivalent conicity in one reprofiling cycle of various EMU trains,which provides guidance for the condition-based wheel reprofiling.
基金the support of the National Natural Science Foundation of China (No. 51005189)the National Key Technology R&D Program of China (2009BAG12A01)
文摘In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the actual measured track irregularities and line conditions were considered. The wear depth of the wheel profile was calculated by the well-known Archard wear law. Through this model, the influence of the wheel profile, primary suspension stiffness, track gage, and rail cant on the wear of wheel profile were studied through multiple iterafive calculations. Numerical simulation results show that the type XP55 wheel profile has the smallest cumulative wear depth, and the type LM wheel profile has the largest wear depth. To reduce the wear of the wheel profile, the equivalent conicity of the wheel should not be too large or too small. On the other hand, a small primary vertical stiffness, a track gage around 1,435-1,438 mm, and a rail cant around 1:35-1:40 are beneficial for dynamic performance improvement and wheel wear alleviation.
基金supported by the National Basic Research Program of China (Grant 2011CB711103)the National Natural Science Foundation of China (Grants U1134202,U1361117)+2 种基金the Program for Changjiang Scholars and Innovative Research Team in University (IRT1178)the 2014 Doctoral Innovation Funds of Southwest Jiaotong Universitythe Fundamental Research Funds for the Central Universities
文摘The fexibility of a train's wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel web,a specifi coupling of wheel–rail contact with a fexible wheelset is presented and integrated into a conventional vehicle–track dynamic system model.Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelset bending and axial deformation of the wheel web on wheel–rail rolling contact behaviors.Excitations with various irregularities and speeds were considered.The irregularities included measured track irregularity and harmonic irregularities with two different wavelengths.The speeds ranged from 200 to400km/h.The results show that the proposed model can characterize the effects of fexible wheelset deformation on the wheel–rail rolling contact behavior very well.
基金This research is funded by the African Centre of Excellence,Energy for Sustainable Development,University of Rwanda,through the World Bank ACE II Program.
文摘This paper posits that a low-speed wind turbine design is suitable for harnessing wind energy in Africa.Conventional wind turbines consisting of propeller designs are commonly used across the world.A major hurdle to utilizing wind energy in Africa is that conventional commercial wind turbines are designed to operate at wind speeds greater than those prevalent in most of the continent,especially in sub-Sahara Africa(SSA).They are heavy and expensive to purchase,install,and maintain.As a result,only a few countries in Africa have been able to include wind energy in their energy mix.In this paper,the feasibility of a novel low-speed wind turbine based on a Ferris wheel is demonstrated for low wind speed applications in Africa.The performance of Ferris wheel wind turbines(FWT)with 61m(200 ft),73m(240 ft)and 104m(341 ft)diameter rims and an 800kW generator are evaluated for selected African cities.The research also compares the Weibull wind distribution of the African cities of interest.A comparison between the FWT and the conventional commercial wind turbines in terms of efficiency,rated wind speed,cost,performance,and power to weight is included.Results show that the FWT has the potential for economic power generation at rated wind speeds of 6.74m/s,which are lower than the average of 12 m/s for conventional wind turbines and have lower power to weight ratios of 5.2 kW/tonne as compared to 6.0-9.2 kW/tonne for conventional wind turbines.
文摘A new method for ergonomic design of a computer mouse is proposed in this paper. In the method, the movements of joints and tip of the forefinger during operating a mouse was captured by a high-speed video camera. The captured videos were ana- lyzed and an algorithm was developed to decide the size and location of the mouse wheel according to ergonomic principles. The al- gorithm was then coded in a software package with Visual C++ and OpenGL languages. Results of the calculation and simulation agreed well with those of the experiments. The software can also be used for shape design of mouse body, buttons and their layouts.