Study On Dynamics Performance Of Flexible Car-body System Of High Speed Train

The emergence of CEMU means that China leads the development of the high-speed railway in the world.With the rapid development of high-speed railway in China,the high requirements on the core technology,manufacturing techniques,as well as running indicators of EMU are put forward.There are three major issues of high-speed railway operations: the stability of vehicle dynamics system,low-power wheel and rail contact and working life of high-speed wheel(repair period).This paper studies the stability of vehicle dynamics system.With the increase of the speed of motor train unit,the range of track excitation frequency becomes larger,simultaneously,the issues such as lightweight car-body vibration and so on are highlighted.Among them,the lightweight aluminum alloy car-body leads the partial or overall body stiffness reduction.Meanwhile,the range of the car body vibration frequency is larger,thus it is easy to generate elastic resonance with the high-frequency excitation caused by high-speed railway.The frequency of the first-order vertical bending vibration of the car-body is close to the sensitive low-frequency resonance region of human body,which seriously affects the comfort of the passengers.The flexible multi-body dynamics system can be used to study the elastic deformation of the structure which makes an effect on large multi-rigid body components moving in large-scale space.Therefore,the introduction of flexible body to analyze the dynamic system performance of high-speed train has a very important theoretical significance in the riding comfort of high-speed train and ensuring the safety of its operation.CRH2 is studied in this research,and the rigid body is regarded as the vehicle components and rails,the relationship between the vehicle parts and the wheel-rail contact is simplified in the mathematical modeling,building a 42-DOF single-vehicle model.Three vehicles are composed of a unit,which can establish a dynamic model composed by multi-rigid body.In this paper,the car body is regarded as box-type and beam structure which composed by traction beam and reinforced chassis.In the ANSYS,the structural stress analysis of the vehicle body is carried out,and the structural stress calculation is carried out by the methods of Lanczos and Guyan,generating the documents which include the Flexibility of Car-body in the SIMPACK.Finally,the paper build the model of single multi-body vehicle,single rigid-flexible coupling vehicle,multi-body train and rigid-flexible coupling train.The paper designs several typical running conditions of high speed train.The dynamic simulation of four models is carried out from the following aspects: vehicle’s riding comfort and safety,as well as the dynamic characteristics of car-body,etc.The results show that when the vibration of the rigid car-body is near 2.5Hz,it will have a significant influence on the rigid car-body.When the flexible car-body is near 2.3Hz,3.3Hz and 10 Hz,it will have a significant influence on the running stability of flexibility vehicle.The structural damping of the flexible car-body can significantly attenuate the longitudinal vibration of car-body.In the single-vehicle model,the dynamic characteristics of transverse and vertical vibration of the flexible car-body are worse than that of the rigid body,and the vibration characteristics of two car-body models are close when the vehicle’s speed is 250km/h.In the train model,the stability of the head car is poor while the middle car shows the best stability in the train.High-speed train’s closed-end car-side connection device shows strong coupling effects while the train running at high speed,which restrains the horizontal and vertical vibration of the rigid body and enhances the stability of multi-body train;restraining the first-order transverse bending vibration of the flexible car-body is near 2.3Hz,which significantly improves the lateral running stability of the rigid-flexible coupling train model,but increases the vertical bending vibration of the flexible car-body near 2.3Hz and 3.3Hz which leads the stability of the rigid-flexible coupling train model is poor,and the vertical vibration of the middle vehicle is the largest.In the simulation of common braking and emergency braking,the high-speed train can fully meet the needs of the longitudinal comfort and safety of the passengers riding.The structural damping of the flexible car-body attenuates its elastic vibration,so the longitudinal stability of the flexible car-body is better than the rigid body.From the above analysis,the vehicle system should be designed to avoid or improve the car-body’s resonance which is near 2.3Hz,3.3Hz and 10 Hz,and to increase the structural damping of car-body.Reasonable structural design of high-speed train’s car-body can not only to maximize the bearing capacity of car-body structure,but also to reduce the vibration of car-body,meanwhile,the rigid-flexible coupling train model can completely reflect the dynamic characteristics of high-speed train.