| With the continuous improvement of the operating speed of high-speed EMUs,higher requirements have been placed on the safety and economy of railway transportation.As a key component used for bearing capacity and vibration transmission,the nodal point’s stiffness is closely related to vehicle dynamics performance.In view of the current lack of comprehensive understanding of the changes in the stiffness of service nodes and the influencing factors,the lack of dynamic analysis during actual wheel-rail matching,and the lack of in-depth understanding of the relationship between the stiffness of the nodal point and high-frequency vibration.In this paper,the stiffness of the boom joints produced by different lines and different manufacturers was tested for the first time at home and abroad.The combination of test and simulation is used to obtain the range of static and dynamic and analyze its influencing factors;Establish the vehicle-track dynamic model and analyze the impact of the the nodal point’s stiffness on the dynamic performance of the vehicle in combination with the actual wheel-rail relationship;Combined with the theoretical model of equivalent stiffness of a series of suspensions,rail wave grinding line test,wheel polygonal bench test,and the establishment of a rigid-flexible coupling model,the effect of the nodal point’s stiffness of the boom on the coupled vibration of the vehicle at high frequency is analyzed;Multi-objective optimization based on vehicle running stability was conducted through joint simulation with Isight and Simpack software,and was verified from the aspects of dynamic performance and wheel and rail wear.1.The stiffness distribution rule and influencing factors of service nodes are analyzed.In this paper,the test results obtained that the node stiffness distribution range of the three manufacturers after serving 1.2 million kilometers on two high-speed rail lines is 74.5 ～ 163.18 MN / m,the radial stiffness change rate is-38.9% ～ 18.6%,and all follow the normal distribution.By comparison,it is found that the change of nodal point’s stiffness is mainly related to the product type,and the influence of the node structure on the static stiffness of the node is established and combined with the finite element model.2.The influence of service node stiffness on vehicle dynamic performance is studied and the allowable variation range of stiffness in the whole life cycle is obtained.Taking into account factors such as different rail profiles,changes in wheel treads during a cycle of the wheel,and different performance of anti-snake dampers,a vehicle-track coupling dynamic model is established to perform simulation calculations.Combined with the stiffness distribution of the serviced boom nodes obtained from the test,the influence of the stiffness changes on the dynamic performance of the EMUs within the range of the serviced boom node stiffness distribution is analyzed.The study found that the longitudinal stiffness of the node mainly affects vehicle stability and curve wear,and meets the requirements of vehicle operation safety within the range of service node stiffness.The allowable variation range of the longitudinal and transverse full life cycle of the service boom node is 60 ～ 180 MN / m,6 ～ 19 MN / m.3.Discuss the relationship between the stiffness of the boom node and the high-frequency vibration of the vehicle.Firstly,through reasonable simplification of the boom structure,it is found that the longitudinal and lateral positioning stiffness of a series of suspensions is mainly determined by the longitudinal and lateral rigidity of the boom nodes.Secondly,the rail wave grinding line test and the wheel polygon bench test show that the replacement of the old and new arm nodes has almost no effect on the vibration of each component and the main transmission path of vibration energy is "axle box → steel spring → frame".The rigid-flexible coupling model including flexible track and sub-rail components,flexible wheelset,flexible axle box and flexible frame is established.The simulation calculation found that the longitudinal stiffness of the joint of the boom has no significant effect on the wheel-rail vertical force,rail acceleration and axle box acceleration under high-frequency vibration.(4)Multi-objective optimization based on vehicle running stability was carried out,and comparison and verification were conducted according to dynamic indicators and wear.Combined with the response surface model,NSGA-Ⅱ genetic algorithm was used for multi-objective optimization,and the longitudinal and lateral stiffness of the optimized nodes were 41.1 MN / m and 4.295 MN / m,respectively.In the range of 50% change in node stiffness,each dynamic performance index is at an excellent level.After stiffness optimization,the wheel wear can be significantly reduced,and at the same time,the dynamic performance when the wheel is matched with the actual rail after wear can be greatly improved. |
