Analysis Of Installation Strength And Fatigue Of Undercarriage Equipment Of An Intercity Train

The fatigue failure of the equipment structure under the EMU trains,the vibration fatigue failure of the key welds and the failure of the connecting bolts will directly affect the reliability of the train operation,and then endanger the driving safety.As one of the important equipment in the off-vehicle equipment,the cooling unit has the characteristics of complex structure,many welds and low modal frequency,so the fatigue failure probability of the cooling unit structure is high.This paper takes a train cooling unit of an EMU as the research object,evaluates its strength,fatigue strength and bolt strength based on the relevant standards of shock and vibration,and compiles the bolt checking program.The main research contents of this paper are as follows:(1)Based on the finite element method,the structure of the cooling unit is discretized and the finite element model of the cooling unit is established.According to the actual connection situation,the Lanczos method is used to calculate the low-order constraint modes of the cooling unit.The results show that the cooling unit has the lowest The natural frequency is13.45 Hz;(2)According to the IEC 61373-2010 standard,six impact conditions are set,and the quasi-static method is used to evaluate the structural strength of the cooling unit under the six impact conditions.The results show that the safety factors meet the design requirements;(3)Based on the acceleration fatigue cyclic load and aerodynamic load conditions in the BS EN12663-2010 standard,the EN-1993-1-9 standard and the EN-1999-1-3 standard are used to test the fatigue strength of the steel and aluminum parts of the cooling unit.At the same time,the fatigue evaluation of 32 key welds of the cooling unit was carried out again by using the structural stress method.The evaluation results show that the cumulative damage value of the cooling unit steel,aluminum parts and 32 key welds is less than 1,and has a large safety margin;(4)According to the IEC 61373-2010 standard,the random acceleration load spectrum is used as an incentive,and the new method of stressing the frequency domain structure is introduced to the cooling unit welds.Domain structure stress transmission relationship,then calculate the stress of the welding seams to respond to the power spectrum,use the Dirlik method for statistics,combine the main S-N curve analysis of the fatigue life and fatigue damage of the key welds of the cooling unit.The cumulative damage value of the sewing is less than 1,and the fatigue performance of the cooling unit meets the design requirements;(5)For key bolts in the cooling unit structure,the bolt intensity of the "Mechanical Design Handbook" and the "VDI 2230" standard uses the static intensity and fatigue strength of the fatigue intensity,and compares the similarities and differences between the two methods.The verification results of the two methods show that the safety coefficients of key bolts meet the design requirements.Among them,the evaluation process based on the "VDI2230" standard is closer to the actual situation due to the factors considering.In order to facilitate engineering applications,the bolt checking program based on "VDI 2230" standard is written in Python language,the GUI interface is established and the program is encapsulated,and the ANSYS interface is embedded to realize the visual display of results and other functions.