Study Of Vibration Characteristics And Safety Of The High-speed Freight EMU At Speeds Above 250km/h

With an increasing demand for fast freight transportation,the high-speed freight train with speeds above 250 km/h which based on the technology of “FUXING” EMU(electric motor unit)has been developed.Fasteners are installed on the floor of carbody to fix the small containers.The target operating speed of it is as high as 350 km/h.Under high-speed operating conditions,structural vibration may occur between the carbody and the container.Besides,the freight EMU has a higher load compared with the passenger EMU,which will have a certain impact on the safety operation of the train.Based on the above reasons,the “study of the vibration characteristics and safety of the freigh EMU with speeds above 250 km/h” are carried out in the thesis.The main contents are as follows:(1)A “vehicle-container” coupled MBD(multibody dynamics)model is established.Considering the mechanical connection between the carbody and the container,as well as the change of the CG(center of gravity)of the container,the motion equation of the containers,carbody,bogies,wheelsets and other components of the freight EMU are derived based on the theory of vehicle dynamics.A fully rigid “vehicle-container”coupled MBD model and a “vehicle-container” coupled MBD model with flexible carbody are established.The correctness of the model is verified using the comparison method.(2)The vibration sensitivity of the “vehicle-container” coupled system of the high-speed freight EMU,which is affected by the mechanical parameters of the fasteners on the floor of carbody,is studied.Based on the fully rigid coupled model,the influence of the connection parameters of the fasteners on the vibration of the freight EMU is studied.The coupling vibraiton characteristics of the container,the bogie,and the flexible carbody at different speeds running on curves and straight lines are analyzed.The differences of the vibration characteristics of the train considering the“vehicle-container” coupling relationship and regardless this relationship are compared.The FRF(frequency response function)of the bogie to carbody and the carbody to containers with different connection parameters are obtained.The results show that the connection parameters of the fasteners have a great impact on the carbody and container,while,have little effect on the bogie;the results of the model ignoring the coupling between the carbody and container are similar to the coupled model with higher connection parameters;Both the FRF of the carbody to containers and the bogie to carbody are influenced by the parameters of fasteners.Based on the above analysis,the recommended values of floor fastener parameters are given.(3)The influence of the transient crosswind load on the vibration characteristics of the high-speed freight EMU is studied.The crosswind spectrum is established based on the Cooper theory,and the transient crosswind loads with different operation speeds and average wind speeds are obtained.Then,these loads are applied to the“vehicle-container” coupled model to obtain the vibration characteristics of the carbody,the bogie and the container together or separately excited by windload and track irregularity.The results show that the transverse and vertical vibration energy of carbody and container,and the transverse vibration energy of the bogie are concentrated within 5 Hz;the vertical vibration energy of the bogie is greatly affected by the track irregularity,and its vibration energy can be as high as 50 Hz;the vibration characteristics of the container are influenced by its position inside the carbody.(4)The operational safety of the high-speed freight EMU under multi-factor combination conditions is studied.With the orthogonal experiment method,the condition of high-speed railway line and the mass of containers are chosen as variables to execute the orthogonal simulation experiment.The carbody is divided into multiple areas,and the different mass of containers on different areas is considered.The derailment coefficient,the dynamic wheel load reduction rate,and the overturning coefficient are chosen as the safety indexes.With the methods of the range analysis and the variance analysis,the contribution rates of different variables to the safety index are analyzed.Besides,the safety of the train under different lateral offset and different heights of CG is studied based on the unfavorable working condition.The results show that the high-speed freight train meets the requirements of operation safety under unfavorable conditions;the condition of railway line has the greatest impact on the train safety;the mass of container in the center area of carbody has a significant impact on the train safety when the carbody is divided into three areas;the wheel load reduction rate should be monitored as a key index during the operation of the train.The thesis has 105 figures,35 tables,and 193 references.