Study On Vibration And Influential Factor Of Fatigue Lifetime Of CRH3High-speed EMU Motor-hanger

Motor-hanger is an especially vital component of CRH3high-speed EMU train, whose fatigue strength and structural reliability have an important impact on the security of train operations. But in vehicle’s service, the motor-hanger works in a deteriorated conditions due to influence of a number of factors and the dynamic load increases for elastic vibration of some parts on the motor-hanger.The reliability assessment indicates that its service life does not meet the design life limit.According to finite element method and rigid-flexible coupling multi-body dynamics, this paper established two kinds of accelerating models based on considering the flexibility of motor-hanger and bogie frame as well as the influence of gear meshing vibration:the kinematic model with gear transmission system and model using control module for acceleration. By setting a variety of operating conditions, the dynamics simulated results of motor-hanger and large nodal stress time histories are obtained. In order to obtain the effect of the curve radius, speed, suspension parameters on vibration and stress of motor-hanger, the paper analyses the simulation results in time domain and frequency domain, and then study their impact on fatigue damage of hanger. The research was supported by the following conclusions:(1) After considering the vibration characteristics of gear, the dynamic load (acceleration, dynamic stress, etc.) of motor-hanger significantly increases and its vibration intensifies. Therefore, in the study of structural vibration problems of high-speed train or fatigue reliability assessment of structures by calculating the dynamic stress, in addition to considering the flexibility of structure, the influence of gear transmission system should also be taken into account.(2) With the decrease of curve radius and improvement of train speed, the vertical vibration of motor-hanger reinforces. Compared to the suspension parameters the service train adopted, under the premise of meeting the vehicle’s dynamics performance, appropriately selecting the smaller suspension parameters is conducive to reducing the vertical vibration of hanger. Vertical vibration of motor-hanger in each simulation condition is affected by frequencies with large amplitude and the hanger also has light local resonance with high frequency.(3)Under the same mileage, the equivalent stress amplitude and fatigue damage of nodes on motor-hanger increases with the decrease of curve radius, improvement of train speed and increase of suspension parameters. Under the premise of meeting the vehicle’s dynamics performance, appropriately selecting the smaller suspension parameters of motor-hanger is conducive to reducing the stress level and fatigue damage of large stress position on motor-hanger. Comparing the simulation results of vehicle with motor-hanger suspended with parameters25MN/m and running at speed of300km/h, the influence of speed to fatigue life of motor-hanger is slightly larger than curve radius and suspension parameters.By studying the fatigue life reliability assessment results of motor-hanger in line test, considering the flexibility of motor-hanger and bogie frame and vibration characteristics of gear, this paper analyses the influence of curve radius, speed and suspension parameters to vertical vibration and fatigue damage of motor-hanger, which will provide guidance and method for in-depth research to fatigue life influential factor and safety and reliability design of vehicle structure.