Effects Of Surface Imperfection To Spring Fatigue Life

Spring is one of the key components of bogie in vehicle, the stability of which affect the safty and stabilization of vehicle operation. There is very large randomicity in fatigue life of spring for the complicated status of load and work environment. For its importance of practical application, the problem catches many engineers to research.Because of the unperfective manufacture technics, various imperfe-ctio ns are found on the surface of spring. It promotes the crack and there is very large effect to crack growth rate. Finally, spring is destroyed. This pa per mainly research about the problems of fatigue life which based on the imperfections of spring:Firstly, through summarizing the speciality and crack type of spring, we obtain the general disciplinarian of spring crack,Secondly, research with the vehicle produced by ZLC. We conclude the main complication of rupture on spring .Bring forward the means of betterment for spring.finally, we combine the theory of fracture mechanics with the method of finite element analysis, aim to the imperfections of spring, with crack size, imperfection size and stress intensity factor as parameter, using the method of finite element analysis, calculate and compare the relation of the three parameters, then obtain the effect of surface imperfection to fatigue life of spring and variety trend.It is find that:â‘ The max of stress intensity of factor is on the deepest point of crack, it have lower direction to nearby the surface of spring.â‘¡The stress intensity of factor will be more and more bigger with the crack expand.â‘¢The stress intensity of factor will be more and more bigger when h/R become more and more bigger. Because of that, the deeper imperfections on spring surface, the shorter fatigue life we have.