Strength And Fatigue Analysis Of The Intermediate Car Body Of An Urban Rail Vehicle

With the rapid development of urban rail transit in China,the structural design of urban rail vehicle has put forward higher requirements.This paper takes the intermediate car body of an urban rail vehicle as the research object,and carries out systematic analysis and research for the strength and fatigue of this car body in the design stage,mainly including the following aspects:(1)Firstly,we study and summarize the relevant domestic and foreign research technology lines and methods on the structural strength and fatigue of an urban rail vehicle,and propose the research technology lines and key technologies suitable for the research object of this paper.(2)For the complex structure of the urban rail car body,the finite element method is used to establish the finite element model of the intermediate car body of the car.The fine modeling is carried out at the key locations and load application locations,and the number of cells of the model is 2483954;the number of nodes is 2211115.(3)In order to examine whether the stiffness distribution and modal frequencies of the car body structure are within the safe range,the first sixteen orders of the free and integral modes of the car body aluminum structure were calculated.The first-order torsional vibration frequency of the free mode of the car body is 14.093Hz,the first-order vertical bending vibration frequency is 16.135Hz,and the first-order vertical bending frequency of the complete mode of the car body is 8.183H_Z,which is staggered with the main frequency of the bogie vibration and meets the requirements of the modal frequency.(4)To establish 12 working conditions of the urban rail vehicle body strength calculation based on EN 12663 standard.The calculation results by the finite element method show that the strength at the upper and lower door corner welds and bolster welds of the urban rail car body side doors do not meet the requirements,and the structural design needs to be improved.In this paper,a structural improvement technique based on a nonlinear model of the local structure of the urban rail car body is proposed based on the sub-model method.The technique is used to improve and verify the local structure of the intermediate car of the urban railcar,so that its strength meets the requirements of the standard.(5)In order to analyze the fatigue of the body welds of this urban rail vehicle more comprehensively,this paper applies the EN 1999-1-3 standard and IIW standard based on the nominal stress method and the relatively new structural stress method to evaluate the fatigue of the critical welds of this urban rail vehicle respectively.Comparative analysis reveals that the two fatigue assessment criteria based on the nominal stress method have basically the same assessment results,while the structural stress method takes into account the effect of local stress concentration in the weld on fatigue,and its calculation results are more conservative compared with the nominal stress method.(6)In order to analyze the influence of the large mass suspension equipment of this vehicle on the structural strength of the C-slot,a complete simulation model of the equipment box and three other simulation models with different degrees of simplification were established and calculated,taking the traction transformer and converter as examples.The results show that the complete simulation model of the equipment box can simulate the local load transfer and force situation of the equipment connection parts clearly and consider the influence of local stress concentration,and its calculation results can better reflect the actual situation,while the simplified simulation model cannot consider local stress concentration,and its evaluation results tend to be optimistic,and the structural design based on this evaluation result has safety hazards.(7)Based on the VDI 2230 standard for strength calibration of traction converter mounting bolts for car suspension equipment under the urban rail vehicle,simulation models with three different simplifications were established and calculated in order to examine the effect of response between adjacent equipment under impact loads.The results show that the large mass of equipment under the urban rail vehicle will cause a certain amount of deformation in the floor of the urban rail vehicle that affects the distribution of bolt loads on adjacent equipment when subjected to impact loads,so it is recommended that the adjacent equipment be modeled and evaluated together during the evaluation of the bolts.