Research On Structure-Connection-Performance Integration Multi-Objective Optimization Design Method Of Multi-Material Assembled Wheel

Automotive lightweight is an important technical way to achieve energy saving and emission reduction,and the lightweight of the wheel is an important part of vehicle lightweight.With the successive application of high-strength steel,aluminum alloy,magnesium alloy and carbon fiber reinforced polymer(CFRP)wheels,the concept of multi-material assembled wheel structure with better performance has been proposed.However,the development and application of multi-material assembled wheels is a complex system engineering involving material selection,structural design,connection design,electrochemical corrosion and process matching.A systematic design process has not yet been established.Therefore,the structural design,performance analysis and evaluation,and structure-connection-performance optimization and matching are the key technologies for the design and development of assembled wheel,and are also the research hotspots and difficulties in the development and design of lightweight wheel structure.This paper takes the 16×6.5J wheel as the research object,and proposes representative design schemes of magnesium/aluminum alloy assembled wheel with punching-forming riveting connection and CFRP/aluminum alloy assembled wheel with bolt connection.The finite element(FE)models of the assembled wheels are established,the fatigue and impact performance analysis methods of the assembled wheels are constructed based on the fatigue and impact theory,and their evaluation indicators are determined.According to the research sequence of“single joint to multi-joint wheel structure”,the matching multi-objective optimization design of single joint coupling material-structure-process parameters and the structure-connection-performance integration multi-objective optimization design of assembled wheels are conducted to construct the systematic structure-connection-performance integration multi-objective optimization design method of multi-material(aluminum/magnesium,CFRP/aluminum)assembled wheel based on mechanical connection(bolt connection,rivet connection),which provides a technical reference basis for the independent research and development of lightweight assembled wheels.Firstly,a three-zone symmetrical stacking lay-up structure of CFRP rim is proposed.Fiber Sim software is used to establish the lay-up model of the rim,and the lay-up information is seamlessly input into the FE analysis software to establish the FE model of the CFRP rim.The FE models of the CFRP rim and the aluminum alloy spoke are assembled by connecting bolts to obtain the carbon/aluminum assembled wheel.In accordance with the requirements of national and industry standards,the simulation analysis of bending fatigue,radial fatigue,13°impact and90°impact of the carbon/aluminum assembled wheel is carried out,and the fatigue and impact damages of the carbon/aluminum assembled wheel are analyzed,and further the indicators for evaluating the fatigue and impact performance of carbon/aluminum assembled wheel are proposed,and then the areas where CFRP rim need to be thickened and thinned are determined,which laid the foundation for the optimization design of the assembled wheel in the following chapters.The load-bearing and deformation modes of the joints of carbon/aluminum assembled wheel are analyzed to provide a basis for the design of the carbon/aluminum joints below.Secondly,quasi-static shearing and drawing and dynamic impact schemes of CFRP/aluminum alloy bolt joint are designed,and the damage modes of bolt joints under static shearing and drawing,dynamic impact on the bolt and dynamic impact on the CFRP sheet are analyzed.It is proposed to use the maximum sharing and drawing forces and the maximum impact forces to evaluate the static and dynamic performance of the bolt joint.The structural parameters of the CFRP and aluminum connecting sheets,the connecting process parameters of the connecting bolts,the lay-up thickness-angle-sequence parameters of the CFRP sheet are selected as the design variables,and the composite structure engineering manufacturing constraints are used as the optimization constraints,and the static and dynamic performance of the bolt joints and the number of lay-ups of the CFRP sheet are determined as the optimization objectives,the matching multi-objective optimization design for the bolt joint is conducted employing the NSGA-II multi-objective optimization algorithm and the RBFNN surrogate model,and the Pareto solutions are obtained.Entropy-TOPSIS method is adopted to determine the best compromise solution and determine the best design parameters to provide a basis for subsequent wheel optimization.Subsequently,the single lap and cross lap specimens of aluminum/magnesium alloy punch-forming riveting joint are designed,and the punch-forming riveting-pull out/shear mechanical performance integrated simulation analysis method of the rivet joint is established,and the forming quality and pull out and shear mechanical properties of the riveting joint are analyzed,the dimensions of punch-forming riveting joint,the relative interference of key measuring points and the uniformity of the relative interference,the maximum pull out and shear forces,and the damage modes and locations of the joint obtained through simulation and experiment are compared to verify the accuracy of the simulation models.The material parameters,structural parameters and connection process parameters of the punch-forming riveting joint are selected as design variables,and the forming dimensions,maximum pull out and shear force,and the maximum amount of interference associated with fatigue damage are selected as the optimization objectives.Taguchi-PCA/FRST/Entropy-GRA method is employed to conduct the matching multi-objective optimization design of the riveting joint,the optimization results under the three weighting methods are compared,and then the best design parameters are determined,which provides a basis for the design and optimization of the aluminum/magnesium assembled wheels described later.Then,according to the optimized design parameters of the rivet joint,the initial design scheme for the punch-forming riveted magnesium/aluminum assembled wheel is determined,and the dynamic explicit punch-forming riveting-implicit springback-implicit bending and radial fatigue strength/explicit 13°and 90°impact simulation analysis method is proposed,the fatigue and impact performance of riveted magnesium/aluminum assembled wheel are studied,and key indicators for evaluating its performance are constructed.The connection process parameters of the wheel joints are selected as design variables,and the fatigue and impact performance of the assembled wheel are determined as the optimization objectives.The connection-performance multi-objective optimization design of the riveted assembled wheel is carried out using the Taguchi-AHP/PCA/Entropy-GRA method.The optimization results under the three weighting methods are compared,and the best combination of design parameters are determined.After verification,the fatigue and impact performance of the optimized magnesium/aluminum assembled wheel meet the requirements of national and industry standards.Then,the lay-up design method of variable thickness CFRP rim structure using the strategy of global lay-up coupling with local lay-up is proposed.The strategy of“sub-area guideing lay-ups gradually eliminated”is employed to realize the coupling of lay-up thickness and sequence,and then the lay-up thickness and angle are simultaneously selected as design variables,which realizes the integration optimization design of the lay-up angle,thickness and sequence of CFRP rim structure.The structural parameters of aluminum spoke and CFRP rim,connection process parameters of connecting bolts,lay-up angle-thickness-sequence parameters of CFRP rim are selected as design variables,and the fatigue and impact performance of carbon/aluminum assembled wheel and the number of lay-ups of CFRP rim are determined as the optimization objectives,the variable thickness composite structure engineering constraints are used as the optimization constraints,the structure-connection-performance integration multi-objective optimization design of the carbon/aluminum assembled wheel is carried out employing the QRSM-RBFNN surrogate model and the NSGA-II multi-objective algorithm,the Pareto solutions are obtained,the optimal compromise solution is screened out using the PCA-GRA decision-making method,and the final optimal design scheme is determined.Comparative analysis of the fatigue and impact performance of the carbon/aluminum assembled wheel before and after optimization is conducted to verify the effectiveness of the integration multi-objective optimization design.Finally,according to the optimization solution,the CFRP rim is manufactured using the forming process of autoclave coupling with molding,and assembled with the forged aluminum alloy spoke through steel bolts to obtain the carbon/aluminum assembled wheel.In accordance with national and industry standards,the carbon/aluminum assembled wheel are subjected to the dynamic bending fatigue,dynamic radial fatigue,13°facing spoke and facing window impact,and 90°impact(E₁ and E₂ impact energy)tests.The results showed that the fatigue and impact performance of the carbon/aluminum assembled wheel meet the requirements of the national and industry standards.The simulation analysis results of the carbon/aluminum assembled wheel are further extracted and compared with the tests to verify the accuracy of the simulation models and the effectiveness of the integration multi-objective optimization design.