Research On Vibration And Fatigue Of Carbody For EMU Under Service Environment

With the successful development of high-speed railway in the country for the past few years,it has become an important postcard in China.The successful operation of "Renaissance" Electric Multiple Unit(EMU)indicating that the high-speed train technology of China has been from the initial introduction,digestion,absorption stage into a fully grasp and re-innovation high-speed development stage.Carbody is the main structure of EMU with the smallest rigidity,and the lghtweight requirements of which is severe.The Vibration level and fatigue strength has always been the focus of EMU technology research as it is a direct structure for carrying passengers.In most operating area and running time,the high-speed EMU can maintain a good running quality,but occasionally there will be abnormal vibration problems occurs,which seriously affecting the ride quality and structural reliability.How to establish an accurate EMU simulation model to reproduce the problem and put forward effective measures is the core of the current research.Based on this,the focus of this paper are placed on the vibration and fatigue of EMU carbody under the service environment.The main work are as follows:(1)The operational modal test of the EMU carbody under service environment is carry out,and the mode parameters are identified,and the equipped carbody modeling method is studied.Based on the particle swarm optimization algorithm,the finite element model updating program is compiled,and a finite element model updating method of EMU equipped carbody is given,which could insure the simulation model of carbody with accurate modal information.(2)Based on the updating carbody model,the condition of carbody resonance is studied,and the judgment factor of carbody resonance is defined.The dynamic model of the rigid-flexible coupling system of the EMU is established,based on the measuring data of the wheel profile and the rail profile,the actual problem of the carbody abnormal shaking phenomenon is reproduced.This paper analyzes the causes of abnormal shaking,and based on this,the concrete measures to suppress the elastic vibration of EMU carbody are studied,and the design principle of carbody mode matching is studied.(3)A method for calculating the vibration fatigue dynamic stress of EMU carbody is studied,and the calculation formula of vibration fatigue stress considering the load phase under multi-load input condition is deduced,which is verified by the experimental data.In the dynamic stress simulation method,the load is divided into two parts: low frequency and high frequency,and quasi-static method and modal superposition method are used respectively to solve the stress.Based on the finite element commercial software,the load-stress frequency response function is calculated by modal superposition method,which takes into account the real part and the imaginary part.Based on the the rigid-flexible coupling dynamic model of the EMU,the carbody input loads under different wheel and rail matching condition are simulated.Through the compilation of the stress calculation program,the dynamic stress time histories of the carbody under the multi-load input condition are simulated by the derived dynamic stress calculation formula.At last,the fatigue strength of the carbody is carried out according to the stress simulation results.