Fatigue And Reliability Analysis Of Primary Steel Round Spring For Fast Metro Vehicles

In view of the frequent fracture of the primary steel round spring of the fast metro vehicle in a city,On the basis of analyzing and processing all kinds of data,searching for the relevant literature,combining with the existing research results,we plan to start with the performance parameters of the primary steel round spring itself,and considering the operation environment of metro vehicles,the random factors of parameters and the actual working conditions,to model and analyze the fatigue and reliability of the primary steel round spring.The main contents of this paper include the following aspects:(1)Based on the prototype of a series of steel round spring of a city’s fast metro vehicle,the 3D model of the spring is built by using UG 3D modeling software and relevant data,which adds contact pairs to simulate the actual working state of the spring.According to the specific situation of the spring model,the appropriate grid type is selected for grid generation and the grid quality is evaluated.Both evaluation results show that the grid quality is good.In order to ensure the accuracy of the spring model,the stiffness of the model is checked.After calculation and analysis,the error between the theoretical stiffness of the spring and the calculated stiffness of the finite element analysis is about 0.98%,which meets the engineering requirements.The theoretical shear stress of static strength calculation is very close to the maximum shear stress of finite element analysis,and the location of the maximum shear stress of finite element analysis is near the inner side of the spring by 1.6 cycles,which is very consistent with the engineering practice that most of the failure points of the primary spring are one to two cycles.(2)According to the S-N curve of spring material and the processed load spectrum file,considering the factors that the passenger flow of metro vehicles may be too large,the overload plus 10% load condition is added on the basis of three major working conditions of no-load,full load and overload,and the minimum fatigue life of spring under sixteen working conditions is analyzed and calculated incombination with the wheel rail corrugation.According to the results,it is found that the fatigue life of spring is affected by wheel rail corrugation It has a great impact,and the minimum fatigue life under the condition of overload plus 10% is seriously reduced,some are even less than 100000 km,which is very similar to that when the primary spring of a metro vehicle breaks,some even drive more than 90000 km.Therefore,it is suspected that the overload of the metro vehicle is another inducement that causes the primary steel spring to work under overload until it fails prematurely.(3)Considering the random factors of spring parameters,taking the spring parameters as the input variables and the minimum fatigue life as the output parameters,the correlation study is carried out.The main parameters that affect the minimum fatigue life of spring are spring wire diameter.Then the DOE test design is carried out to explore the relationship between the spring parameters and the minimum fatigue life,and the response surface analysis is carried out by using the standard response surface method to evaluate the response surface results to ensure its accuracy.Finally,reliability analysis is carried out to obtain the cumulative probability and variance level of the minimum fatigue life of the spring in each stage.