Prediction Of Weld Fatigue Life For B-type Subway Car Body

In recent years,with the continuous development of China’s economy,the urban scale is expanding rapidly,so far,the number of motor vehicles has reached 402 million,of which 79 cities have more than 1 million,resulting in urban traffic pressure increasing year by year.While the subway effectively alleviated the problem by virtue of large transportation volume,fast speed,and many shifts.However,as metro vehicles continue developing towards heavy load,lightweight and fast,higher requirements are put forward for the fatigue strength of the car body.As the main structure to accommodate passengers,its fatigue life has always been the focus of research.For B-type subway car body,due to random track excitation,the position where fatigue fracture occurs in the early stage of the car body is mostly at the weld feet.Therefore,the paper predicted the fatigue life of B-type subway car body based on the structural stress method.Firstly,the finite element model of the car body was established by using Hyper Mesh software,and modal analysis and static strength analysis were conducted.Secondly,according to the structural characteristics and dynamics parameters of the vehicle,the rigid multi-body model of the vehicle was established by using Sim Pack software.Apply German orbital spectrum to the model and the time domain integration was carried out.The time-load course at the air spring was extracted as the excitation load for fatigue life calculation.Then,amended the time domain load,based on the quasi-static structural stress method,a Matlab self-compiled program for predicting weld fatigue life of car body is developed,to predict the fatigue life of13 key welds,the results show that the fatigue life critical welds meet the design requirements.Finally,using submodel technology to optimize the toe size of dangerous welds,and the fatigue life of weld was determined to be the highest when the size of weld foot was 5.5mm.