The curve passing and stability optimization of locomotive bogies with coupled wheelsets are studied by Bombar Mountain er Company of Switzerland. As we all know, in the traditional vehicle design, curve passing and stability are a pair of contradictions. Researchers have used many methods to improve these two basic properties simultaneously. In this paper, a wheelset cross-coupling mechanism is developed, which separates the steering and traction transmission functions of wheelsets, and has been successfully applied to 460 series locomotives of Swiss Federal Railway Company, and the wheelset turnover period has been extended by 3 times to 14 times.
Wu of Transportation Technology Center (USA) has studied the influence of friction between the center plates of freight car bogies on curve passing and lateral stability, and evaluated the lubricating materials of the center plates currently used. The main results are as follows: (1) Under normal vehicle and rail conditions, the lubrication condition of the center plate has little influence on the lateral force of wheel and rail;
(2) For freight cars with rolling contact side bearings (RSB), the friction coefficient of the center plate has an important influence on the lateral stability of the vehicle. In order to reduce the danger of truck hunting, the friction coefficient of the center plate should be at least 0.3;
(3) Constant contact side bearing (CCSB) can effectively improve the lateral stability of freight cars. For side-bearing trucks with frequent contact, the friction between the center plates has little effect on the vehicle instability speed;
(4) The simulation results show that the average speed of hunting instability is 65438±06km higher than that of rolling bearing. (5) Polyester has a good application prospect as the friction material of the center disk.
In addition, Y. Handoko of Queensland Central University in Australia used vampire software to study the influence of asymmetric braking force on the curve passing performance of freight cars for the first time. They simply use the 1 time of the positive and negative rocking power railway vehicles in Volume 42, 2004 to simulate the effect of asymmetric braking force. The results show that if the negative rolling moment is applied when the freight car passes through the curve, the angle of attack and the lateral force of wheel and rail will increase, which is not conducive to the curve passing.
2 Research progress of vehicle motion stability
The nonlinear motion stability of vehicles is a very theoretical research field, even involving deep-seated concepts such as chaos and bifurcation. In recent two years, the international research on this subject is still mainly theoretical research, but some new viewpoints have emerged, such as the motion stability on curves and the influence of track system on vehicle motion stability.
Based on the study of nonlinear motion stability and bifurcation of bogies, H. True of Danish University of Technology further analyzed the dynamic stability of freight car wheelsets with dry friction suspension damping.
F. H of Xiahe Danmai University of Technology in Australia has studied the dynamics of three-piece freight car bogies. The main feature is to consider the two-dimensional dry friction characteristics of wedges (previously simplified as one-dimensional problems), and calculate the linear and nonlinear critical speeds of three-piece freight car bogies as 102.6km and 73.8km respectively. The calculation results show that the three freight car bogies exhibit chaotic motion.
Y. Sun of Australia emphasized the importance of considering the track discrete support model when calculating the hunting stability of freight cars. The results show that the critical speed of hunting instability calculated by considering viscoelastic trajectory model is lower than that calculated by not considering trajectory model (i.e. "rigid" trajectory), which is generally lower than 10%. It is worth pointing out that this work was completed by China Southwest Jiaotong University as early as two years ago. They use the vehicle-track coupling dynamics method to solve the critical speed of vehicles. The results show that the difference between the critical speed of vehicles and the railway parameters in China is less than 8% (the critical speed is lower when considering the actual track elastic structure), and the results are similar. The research results question the calculation of vehicle critical speed in the classical vehicle dynamics calculation method (without considering the elasticity of track structure). Because the classical method will overestimate the driving stability of the vehicle, it is dangerous.
J Arn0 1d of DLR, Germany, discusses the influence of wheel elasticity on the running performance of railway vehicles, and thinks that the structural elasticity of wheelsets will lead to greater lateral amplitude than rigid wheelsets, which will also affect the running performance of the whole vehicle.
K. Noinski of Warsaw University of Technology in Poland thinks it is necessary to consider the motion stability of railway vehicles on curved tracks. Prior to this, people generally studied the stability of vehicle motion in view of the lateral stability of vehicle self-excited vibration on straight track. Curved track (radius and superelevation) is considered as the external disturbance source, which suppresses the self-excited vibration, so this paper is bound to cause some controversy.
G. Schupp theoretically discussed the possibility of applying numerical bifurcation analysis method of mechanical system to the motion stability of railway vehicles.
3.2 Foreign application
New york subway l 080 new car, adding 200 new cars every year; Thousands of heavy cargo trains in the United States, Canada, South Africa and other countries; J.R.Evans analyzed the causes and preventive methods of wheel-rail rolling contact fatigue (RCF) from the perspective of vehicle dynamics. Firstly, a quasi-static curve is established, and the effects of vehicle suspension design, wheel-rail tread, lubrication and vehicle speed on wheel-rail rolling contact fatigue are given through simulation analysis. Secondly, dynamic simulation analysis is more helpful to determine the contact conditions that cause RCF, and can analyze the influence of track geometric irregularities on RCF.
Frohling of South Africa's SPOORNET introduced the wheel tread wear and rolling contact fatigue under the condition of large axle load (30t) from theoretical analysis and application experience. This study is mainly based on the theoretical analysis of serious wheel wear and tread peeling damage of UNO, a new type of freight car operating in Sweden, and finally puts forward a scheme to redesign the wheel shape.
In addition, J. B. Ayabse and H.C.1\ 011et of France have studied the solution method of wheel-rail contact point under the condition of half hertz. British I.Persson and others use genetic algorithm to optimize the shape of railway wheels, and think that this method can be used for rail section optimization and wheel-rail shape matching research.
4 Research progress in other fields of vehicle system dynamics
At this international conference, other papers related to vehicle system dynamics were read and exchanged, mainly including vehicle suspension (active), pantograph-catenary dynamics and vehicle aerodynamics. Relatively speaking, the number of papers in these areas is small, but it also shows some new problems in the research of railway vehicle system dynamics.
4. 1 vehicle suspension
In order to improve the curve passing performance and motion stability of the vehicle under the same PIRE, an auxiliary spring (transverse spring) is added to the secondary suspension of the vehicle, and the dynamic simulation is carried out by using the software Vapengpire. The results show that this measure can reduce the steady lateral acceleration of the car body when the high-speed curve passes.
Wu Pingbo of Southwest Jiaotong University in China adopted a flexible car body model.
The dynamic response of bus considering semi-active suspension is studied. The first-order vertical bending, first-order lateral bending and first-order torsion modes are considered in the car body model, and other parts of the car are still regarded as rigid bodies. The vertical and lateral ride comfort indexes of rigid and flexible models are calculated and compared, and the semi-active suspension test is carried out on the rolling vibration test bench.
Japanese H. Nun Ashima and others tried to improve the ride comfort of (>: t (automatic rail transit) vehicles. The active control of lateral force is realized by using Ho control theory. The simulation results show that the ride comfort of A (reserved vehicle) is obviously improved.
4.2 Pantograph-catenary dynamics
Sweden's P. Harell and others have studied the influence of the superposition of catenary sections (Figure 8) on pantograph-catenary dynamics under the condition of multiple pantographs, which has not been reported before. Overlapping area of catenary
Blue Mountain in South Italy, etc. This paper discusses the dynamic interaction between intermediate frequency and high frequency of pantograph-catenary system, mainly analyzes the relationship between pantograph-catenary contact force and off-line, the influence of suspenders on contact force and the causes of irregular wear of contact lines.
4.3 aerodynamics
Italian F. Cheli and others used numerical simulation and wind tunnel test methods to study the aerodynamic load acting on the railway vehicle body and its corresponding vehicle response under a given wind field.
Suzuh meter al. of Japan Railway Institute of Comprehensive Technology studied the interaction between vehicle vibration and aerodynamic force when the train runs in the tunnel and the countermeasures to reduce the additional vibration caused by aerodynamic force.
5 vehicle system dynamics research prospect
To sum up, in recent two years, the international research on railway vehicle system dynamics has made remarkable progress, especially in improving vehicle curve passing performance, improving vehicle running stability and solving
The research on the practical problems of vehicle microchannel interaction is very active, and many new methods and technologies have been developed. Combined with these research progress, the author thinks that the following aspects will lead the new progress of international railway vehicle system dynamics research, which Zhai Wanming will pay extensive attention to and further develop:
(1) With the rapid development of trains, the methods, approaches and technical measures to comprehensively solve the stability of straight-line motion and curve passing performance of vehicles will continue to be one of the hot spots for researchers of Guangzhou-Dali Railway.
(2) Active control technology is an effective method to improve the running quality of railway rolling stock, which has been widely used in developed countries. However, with the further intensification of competition among railway transportation, air transportation and road transportation, it has become the goal pursued by modern railways to continuously improve the running speed and ride comfort of trains. The means to achieve this goal is to adopt advanced active control technology to a great extent. Therefore, this field has broad development prospects.
(3) The theoretical research on wheel-rail contact is becoming more and more perfect, and there are more and more problems caused by wheel-rail rolling contact in wheel-rail transportation system. Therefore, how to reasonably apply the wheel-rail system dynamics (vehicle track system dynamics) theory to study and solve these practical problems (such as irregular wheel-rail wear and rolling contact fatigue) will surely become an important aspect in this field. In order to solve the problem of irregular wheel-rail wear, it is necessary to develop a comprehensive model that considers the high-frequency interaction and damage mechanism of vehicles and rails at the same time.
(4) The study of vehicle-rail interaction has been able to reflect various practical factors in the railway more and more, and will be further applied to practical projects in the future, such as track design of bridge-head transition section of high-speed (fast) railway, research on dynamic action of heavy-duty trucks on the line, prediction of wheel-rail wear and track settlement, derailment study of vehicle-ramp dynamic interaction and determination of safety evaluation standards.
(5) The influence of aerodynamic effects on the vibration performance of high-speed trains (especially when passing through tunnels) has been paid more and more attention, and further improving ride comfort (including reducing noise) is an unavoidable research topic.
(6) Dynamic simulation technology has been widely used in the international vehicle system dynamics research and application field, and has played a huge role. Various vehicle dynamics simulation software is becoming more and more mature. China should pay attention to this trend, organize the development of various large-scale general dynamic software, and provide scientific tools for the optimization of locomotive and rolling stock dynamic performance. At the same time, we must attach importance to the experimental verification of simulation software, and only widely verified software can be used to guide production practice.