| The wheel is the most important load bearing and safety part in the driving system of a car,and the loads and working conditions are complicated in the work.As an unsprung mass and the main rotating and moving part of car,its lightweight design is more significant for the automobile energy saving and emission reduction,which can more effectively improve the whole car's lightweight level.But at the same time it is very easy to reduce the mechanical properties of the wheel.The level of lightweight and the comprehensive performance of the wheel directly affect the economy,power,maneuverability,comfort,braking and traffic safety of the car.Therefore,in the lightweight design of the wheel,it is necessary to consider the influence of the change of the wheel structure on the mechanical properties of the wheel,such as the fatigue,impact and aerodynamic performance.At the same time,the key technology for the development of a new lightweight wheel is the collaborative application of the three methods with composite applications of multiple light alloy materials,improving production and processingtechnologyandoptimizingthestructure.Therefore,the structure-material-performance integrated multi-disciplinary and multi-objective lightweight optimization method,which comprehensively considers the performance of the wheel,is the core technology and hotspot of the wheel lightweight research.In this paper,taking a16?61 2J type wheel as the research object,based on the united topology optimization technology,an assembled wheel composed of a magnesium alloy rim and an aluminum alloy disc is designed.Based on finite element analysis methods of the elastic mechanics,plastic mechanics,fracture mechanics and fluid mechanics,combined with the fatigue theory,impact theory and turbulence theory,finite element analysis models of the assembled wheel are established to study the influence mechanism of the wheel structure on the wheel's fatigue performance,impact performance and aerodynamic performance.On this basis,considering the performance indexes of the mass,strength,stiffness,modal frequency,fatigue life,13°impact performance,90°impact performance and aerodynamic performance of the wheel,based on the surrogate model method,multi-disciplinary and multi-objective lightweight optimization design of the assembled wheels is carried out,and the validity and accuracy of the finite element analysis models and the multi-disciplinary and multi-objective optimization design are verified through tests.This paper establishes a wheel structure research and development process and multi-disciplinary and multi-objective optimization design method for the wheel to provide theoretical and technical basis for the development and optimization of a wheel.Firstly,based on the dynamic bending and radial fatigue test conditions of the wheel,a united topology optimization is carried out to design an assembled wheel.The finite element analysis method is used to study the relationship between the performance parameters such as the strength,stiffness,fatigue life and safety factor of radial fatigue life of the assembled wheel and the wheel structure.The fatigue life of bolts under the dynamic bending fatigue test is calculated and analyzed,and then the type of the bolt is selected.And free modal analysis of the bolted assembled wheel is simulated.Secondly,finite element models of the assembled wheel for 13°impact tests are established to analyze the effective plastic strain of the wheel and elements distribution beyond the elastic deformation limit of the disc material under two conditions of the hammer facing the spoke and the window respectively.And establish finite element models of the assembled wheel for 90°impact tests further,analyzed the deformation of the inner wheel flange and the effective plastic strain of the rim and disc when the hammer impacted facing the window,and analyzed the failure range of the wheel and the effective plastic strain of the rim and disc beyond the 25%circumferential range?90°?of the impact position when the hammer impacted facing the valve window.Then research the influence of structure size on the impact performance of the wheel.Then,finite element models of the assembled wheel and wheels with different discs for aerodynamic analysis are established by using computational fluid dynamics?CFD?method.The DrivAer standard car model and its wind tunnel test datas of the Technical University of Munich are used to determine the calculation scheme of CFD simulation analysis and verify the correctness of the results.The flow field characteristics of the car with assembled wheels and wheel cavity and the heat transfer performance of the brake disc are analyzed.And the aerodynamic performance of wheels with different number,styles and widths of spokes are analyzed.The influence mechanism of the wheel disc structure on the flow field,the aerodynamic drag of the car and wheel and the heat transfer performance of the brake disc are researched.Subsequently,a multi-disciplinary and multi-objective optimization method for the assembled wheel is researched based on the surrogate model method.The parametric models of the assembled wheel under eight simulation conditions are established by using the mesh morphing technology.The Optimal Latin Hypercube Design and Central Composite Design are respectively used to fit the Kriging surrogate model and to validate the fitting precision of the surrogate model in Isight software platform where softwares calculating the performance indexes are integrated.Using the established surrogate model,the Non-dominated Sorting Genetic Algorithm-???NSGA-???is adopted to perform the multi-disciplinary and multi-objective lightweight optimization design of the wheel.The Pareto frontier is obtained,and a compromise solution with lighter wheel mass is selected as the optimization scheme while meeting the various performance requirements of the wheel.Verify the performance of the lightweight multi-disciplinary and multi-objective optimization design results,and research the influence of wheel structure changes on various performance indexes before and after optimization.Finally,the rim and disc samples of the assembled wheel are processed respectively by forging process.Then,the dynamic bending fatigue test,dynamic radial fatigue test,13°impact tests?spoke and window?,90°impact tests?window and valve window?and modal analysis test are carried out.The performance indexes of each test of the assembled wheel are analyzed and evaluated.And the correctness of the finite element analysis and the effectiveness of the multi-disciplinary and multi-objective lightweight optimization scheme are verified by the comparison of the test and simulation results. |
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