Finite Element Analysis And Structural Optimization Of A Certain Automobile Steering System

With the expansion of China's automobile market,the demand for steering systems continues to grow.Among them,electric power steering system(EPS)has been paid more and more attention due to its safety,comfort and environmental protection abilities.In this paper,the finite element method and structural optimization method are used to analyze the column electric power steering system designed and developed by a company,so as to improve the energy absorption characteristics and NVH performance of the vehicle steering system.In this paper,the fishbone diagram of the influencing factors of the compressive force of the steering column was firstly established.Through screening and analysis,it was determined that the design value of interference of the energy-absorbing structure of the steering system was unreasonable,leading to abnormal compressive force of the steering column.In order to get the correct value range of interference,a 3d model of "steering outer tube-sliding bushing-steering inner tube" was firstly established in CATIA software,which was imported into the pre-processing software HyperMesh for geometric cleaning and mesh division.Then,the mesh model was imported into the finite element analysis software ABAQUS,and interference contact properties and boundary conditions were set.The cloud maps of pressures-force on the steering inner pipe and stress distribution on the contact surface of sliding bushing under different interference values were calculated,and the correctness of the finite model was verified by pressure test.Finally,according to the results of finite element analysis,the appropriate value range of interference of steering string energy absorption structure is given.In view of the phenomenon that the steering wheel shakes too much when the engine is idling,the mechanism of vibration transfer of engine idling is firstly expounded,and the vibration frequency of four-cylinder four-stroke engine is obtained by calculating the theoretical formula.Then,a 3d model of the steering system was built in CATIA software,and a finite element model of the steering system was built by geometric cleaning,mesh division,adding material properties and boundary conditions to the 3d model in HyperMesh.Finally,the finite element model was imported into the analysis software Optistruct to conduct constraint modal analysis,and the first six natural frequencies of the steering system were obtained.In order to improve the first-order natural frequency of the steering system,the thickness value of the main plates in the steering system was firstly taken as the design variable.Based on the sensitivity analysis results,the thickness value of the five plates wao determined as the design variables.The method of Hammersley sampling was used to design the experiment,and 30 groups of sample points were obtained.Then,the response surface model of the first order natural frequency of the steering system is obtained by using the least square method.Finally,based on the response surface approximation model,sequential quadratic programming algorithm is used to optimize the steering system structure.The results show that the first-order natural frequency of the steering system after structural optimization reaches over 33Hz,which successfully avoids the engine idling excitation frequency and effectively inhibits the vibration of the idling steering wheel.