Study On Coupled Vibrations Of Carbody And Suspended Equipments For High Speed Trains

With the rapid development of the economy, the transportation has played a decisive role in people’s daily life. As high-speed passenger trains become the carrier to transfer and exchange information between cities, its speed and convenience is increasingly important. The lightening design of carbody and the type of distributed power which is advanced to effectively speed up the vehicle have resolved the stumbling block in increasing running speed. Under normal circumstances, lightening design makes the carbody structure reduced by 30-40% of the weight, which greatly reduces the weight of the whole vehicle and plays vital roles in increasing speed. Furthermore, the distributed power can reduce the axle load and the wheel-rail forces, and also can contribute to controlling the starting and braking of the train. However, the improvement of speed means higher requirements and challenges to the vehicle ride quality and stability. Firstly, the lightening design of carbody usually leads to stiffness deficiency and aggravates elastic vibration, which seriously affect the dynamic performance such as the ride quality or comfort. Secondly, many equipment of the high-speed passenger car are suspended under the carbody. The total mass can reach ten tons or more and occupies a larger proportion of the total weight of the carbody. The weight of an individual device ranges from tens of kilograms to several tons. And some of the devices such as tractive transformer, traction motor and condenser fan and so on have excitation source, which can transmit vibration energy to the carbody directly and even cause local vibration of the carbody. This problem will surely affect the ride quality. Thus, in order to effectively solve the impact of devices on elastic vibration of the carbody, throughcombining the theoretical study and roller rig test, this thesis carries out extensive study on the coupling vibrations between equipment and carbody and gives the principles of the suspension parameter selection and the distribution of suspended equipment.The following works have been carried out in this thesis:1) The simplified rigid-flexible coupled dynamic models for the underneath suspended equipment and carbody coupled vibrations have been set up. The theory of equipments suspended has been researched and the influence has been studied.A suspension element was designed for a specific equipment and the dynamic performance was measured. Based on the test data, a force element which can better reflect the dynamic characteristics of the suspension element was built and applied in the simulation.2) As the structural modes of the vehicle system are closely related to the vibrations, by using the rigid-flexible coupled dynamic model, the effect of carboy, bogie frame and wheel set modal shapes on dynamic performance such as ride quality and stability was studied. Also, the contribution of each mode to the vibration was discussed and the selection method of the modal shapes in the simulation was determined.3) According to the 3D rigid-flexible coupling dynamics model of the coupling vibration of equipment and carboy, the effect of underneath equipment of carbody on the dynamic performance is investigated. Firstly, the vibration responses of carbody using elastic and rigid suspensions for underneath equipment were compared and the necessity of using elastic suspension was pointed out. Secondly, the effect of the weight of equipment, suspension stiffness, suspension damping and suspension position on carbody vibration was discussed and the layout principle of underneath equipment was given. Finally, the two-stage vibration isolation of active devices was studied and the match relationship between the suspension parameters was analyzed.4) Taking the vibration of traction transformer as the research object and through numerical calculation and roller rig test, the performance index such as the carbody acceleration and ride quality were compared under different suspension stiffness for undernearth equipement. The results showed that the theoretical calculations and roller rig tests were in a good match, thus it proved that using elastic suspension for the undernearth equipment was rational and feasible.