| With the increase of speed and load of rail transit vehicles,the operating environment of locomotive components is becoming more and more complicated,which has higher requirements for vehicle safety.The antenna beam is located at the end of the subway bogie frame,which is the bearing structure of the ATP system.During vehicle operation,cracks often occur due to random vibration excitation from the end of the frame,which seriously affects the safety of vehicle operation.Therefore,fatigue analysis of antenna beam is of great significance.In this thesis,the random vibration fatigue of the base metal and weld of the antenna beam structure is calculated based on the three interval method.According to the theory of structural optimization and finite element analysis,the lightweight design of the antenna beam is carried out.The main works finished in this thesis are as follows.(1)This thesis first introduces the related theories of random vibration fatigue,including the characteristics of random process vibration,the power spectral density and the fatigue characteristic curve of materials.In addition,the different processes of time domain and frequency domain analysis methods in random vibration fatigue are expounded.By comparing the characteristics of the two analysis methods,the three-interval method in frequency domain analysis method is finally determined to calculate the random vibration fatigue of antenna beam.(2)In this thesis,the finite element model of the antenna beam is established.The finite element software ANSYS is used to impose fixed constraints on the end of the frame to calculate the modal shape of the structure,and the measured acceleration excitation is applied in three directions.Based on the three-interval method proposed by Steinberg,the fatigue damage of antenna beam is calculated.Combined with Miner linear fatigue cumulative damage criterion and material fatigue characteristic curve,the cumulative fatigue damage in three directions of antenna beam base material and weld is calculated.Through calculation and analysis,under the measured acceleration excitation,the base metal and weld meet the fatigue design requirements,and there is still a certain space for structural optimization.(3)According to the calculation results of fatigue damage,in order to improve the material utilization rate,the lightweight design of antenna beam structure is carried out by using structure optimization software based on structural optimization theory.After optimization,the maximum fatigue damage of the base material of the antenna beam is 0.415,and the maximum fatigue damage of the weld is 0.256,which still meets the fatigue strength requirements.The weight was reduced by 11 % from 135 kg to 120 kg. |
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