The Reserch On Contact And Fatigue Of Primary Spring Of Metro Vehicle Bogie

In order to reduce the harmful impact during vehicle operation,spring shock dampers are installed on the bogies of vehicles.The main function of spring shock damper is to withstand the load of vehicle,and alleviate the lateral and vertical impact caused by track irregularity aiming at improve the stability and safety of vehicle operation.Therefore,as the key component of the spring shock dampers on the vehicle bogie,the reliability of the primary spring is of great significance to the traffic safety.In the investigation of a domestic metro line,it is found that the breakage phenomenon of the primary spring of the metro vehicle bogie is more and more frequent,and the amount of breakage increases exponentially.Although the design life of the primary spring is more than 2 million kilometers,some springs break down after only using 30000-100000 kilometers in fact,which is far less than the design life.After consulting the relevant literature,most of the studies on spring fracture at home and abroad are on the characteristics of spring materials,and few are based on the actual load of the spring in the process of vehicle operation.Therefore,this paper will collect the load data of a series of springs in the process of vehicle operation through onsite follow-up test,focusing on the contact and fatigue life of the primary springs,and explore the causes of their fracture.The main work are as follows:1.The fracture failure and the fracture surface of the primary springs are analyzed,and it is determined that the fracture of the springs belongs to fatigue fracture.At the same time,according to the statistical data of fracture,it is found that most of the failure occurs in primary inner springs,so the main research object of this paper is primary inner springs.2.Using the mechanical properties of spring steel and the basic theory of cylindrical helical spring and the mechanical properties of spring steel studied in this paper,the shear stress of primary inner springs is analyzed theoretically according to the bogie structure and working load table.3.According to the principle and method of primary springs' dynamic displacement and stress-strain,the test data are processed.Some test and data processing results are listed,and preliminary analysis is carried out.It is concluded that the main factor of the primary spring in the running process of the vehicle is the vertical load.4.Using the finite element theory,the finite element model is established,and the static analysis of the model is carried out.By comparing the error between the finite element analysis and the theoretical analysis,the accuracy of the simulation results is guaranteed.At the same time,the contact between the reeds in the primary inner spring is simulated and analyzed.By applying different vertical loads to the simulation model,the change trend of contact area and contact stress is analyzed.5.According to Miner's linear damage accumulation theory and the relevant literature,the S-N curve of primary inner springs is determined.According to the measured load spectrum,on the one hand,the safe operation mileage of primary inner springs is calculated theoretically;on the other hand,the fatigue life of primary springs is simulated and analyzed by fatigue simulation analysis software.The researches show that: During the operation of the vehicle,there is a contact collision between the reeds in the primary inner spring,and the contact collision will lead to the defects of the spring reeds,and the fatigue life of the defects will be greatly reduced.With the operation of the vehicle and the continuation of contact collision,the defects will further worsen,and the fatigue life of the aggravated defects will be further reduced,and even fatigue damage,which will lead to the fatigue fracture of the spring reed.