Study On Fatigue Reliability Of Car Semi-active Suspension Component

Car is a widely used transportation in modern society. In recent years the vehicle speed significantly improved, and the demands of the comfort, handling stability and security of automobile were increased. More and more control systems were used in automobile with the improvements of electron and automatization techniques. Because of its simple structure, wide bandwidth, low consumption of energy and rapid response, the magnetorheological(MR) semi-active suspension had attracted much more attention in the research domain of electronic control suspension. Suspension system has great meanings for vehicle ride comfort and driving safety. The reliability of suspension system parts is an important evaluating indicator of the quality of automobile. Semi-active suspension system is a new type suspension system, and the reliability research of semi-active suspension system parts still very few interiorly. Reasonable fatigue reliability analysis and test techniques on one hand can shorten the design and production cycle of suspension component, on the other hand they can make sure that suspension system can be used continuously and effectively in the real operation conditions.Based on fatigue reliability research of vehicle semi-active suspension component, in this dissertation calculation and simulation of the dynamic fatigue reliability of semi-active suspension lower arm are carried out under the condition of velocity change.Semi-active suspension systems under stochastic optimal control and variable domain fuzzy control are designed. Fatigue life of lower arm of suspension under different control method is calculated. The main research contents of this dissertation are summarized as follows:1)Firstly, the research progress of vehicle semi-active suspension system and reliability as well as fatigue life of vehicle components and parts. The research contents and innovation points of this dissertation are presented.2)Fatigue life characteristics of suspension component material are discussed. Three typical cumulative fatigue damage theories are introduced. Process of fatigue life prediction using nominal stress method and local stress-strain method under different characteristic loads is analysed. The general process and principle of reliability calculation under different characteristic loads are elaborated.3)Vehicle semi-active suspension model of two degree of freedom is studied. The calculation method of statistical regularity of suspension component random dynamic load is derived. Probability model of random dynamic load under variable speed condition is set up. Dynamic fatigue reliability of independent front suspension lower arm is calculated and simulated.4) Finite element model of main component of suspension and the vehicle multi-body dynamics model are set up. The rigid flexible coupling model is set up using finite element flexibility file. Stochastic optimal control strategy for vehicle ADAMS model is designed. Co-simulation of ADAMS and Matlab software is studied. Boundary condition of load of each connection point of lower arm is obtained. Fatigue life of lower arm is calculated in Fatigue software.5) Variable domain fuzzy control method is designed for vehicle ADAMS model. Co-simulation of ADAMS and Matlab software is studied. The load time history of load of each connection point of lower arm is obtained. Fatigue life of lower arm is calculated in Fatigue software.6) Real vehicle test bench of four channel road simulator is carried out. The control effect of semi-active suspension equiped with MRF damper is checked out. Strain signal of lower arm is tested. Fatigue life of lower arm is calculated according to the measured strain signals in LmsTecware software.7) The research contents of this thesis is summarized, and the next step of research is advised.