Fatigue Life Improvement Of Torsion Beam Based On Hot Metal Gas Forming Process

With the rapid development of China’s social economy,automobiles have already been part of our daily lives.In China’s enormous automobile market,small and medium-sized sedans,SUV,and MPV models account for half of the automobile production and sales.Among these models,torsion beam non-independent rear suspensions are widely used in small and medium-sized cars due to its advantages of simple structure,small size,and low cost.In the process of vehicle driving,the working condition of the torsion beam rear suspension is relatively bad,and it is subjected to the combination of bending and torsion constantly.If the fatigue life of the torsion beam rear suspension is not up to standard,it will pose a great threat to the safety of the vehicle during driving.Therefore,fatigue life is one of the most important performance indexes in the design stage of torsion beams.Nowadays,torsion beam is usually produced by hydroforming high-strength steel pipes.Due to the poor plasticity of high strength steel material,weak heat affected zone,large amount of cold forming rebound,and high requirements on equipment bulging force and clamping force,its wide application has brought great challenges to hydraulic pipe forming technology.Faced with the ever-increasing design requirements for the fatigue life of torsion beams,Hot Metal Gas Forming due to its hot forming method,hot metal has better fluidity and lower deformation resistance,the required forming pressure and clamping force are smaller and therefore has certain advantages.Cooperate with a reasonable heat treatment process can effectively improve the torsion beam strength,fatigue life and to achieve the torsion beam of light.This paper takes the torsion beam of a certain vehicle model under development as the research object.Firstly,the finite element model of the torsion beam is carried out,and its free mode was analyzed.The strength of the torsion beam under four extreme working conditions was checked.The structure in dangerous position was analyzed under the premise of the same forming process and materials.Vehicle coupled dynamics model is established to obtain the acceleration process of the rear wheel center within 600 s in the virtual proving ground combined Fatigue strengthen test road.And then translate them into wheel center,trailing arm and body connection,spring and shock absorber installation point of the four hard point load spectrum as input of simulation analysis of Fatigue life.The nominal stress method is adopted to predict the Fatigue life of the torsion beam by MSC.Fatigue.According to the results of the simulation analysis.Using hot metal gas forming way instead to get the torsion beam test pieces.Test the tensile strength by Rockwell hardness of the trial-produced beam and compared with the tensile strength measured by material standard specimen tensile test.By using the new material mechanical performance for input of fatigue life simulation calculation again of the torsion beam.And through the torsional fatigue test combined and real vehicle road test validation,the fatigue life of the torsion beam rear suspension has a significant effect.