Lightweight Design For Liftgate Based On Multi-objective Optimization Method

With the continuous development of China’s auto industry,energy conservation and environmental protection have become the main development direction of automotive research.Lightweight technology is an important way to achieve energy saving and environmental protection.Multi-material multi-objective optimization design can give full play to the advantages of various lightweight materials and meet the requirements of light weight to the greatest degree.In this thesis,the multi-objective optimization method is combined with the lightweight design of the liftgate.Through the multi-objective optimization design,a liftgate lightweighting scheme that satisfies the performance and cost requirements is sought.At the same time,it can also provide reference for the weight reduction of the vehicle body and other components.This thesis analyzes several commonly used optimization algorithms and approximate models in the parameter optimization method.By constructing a nonlinear function example,it is found that the genetic algorithm can find the global optimal solution of the non-continuous and non-differentiable problem without depending on the gradient of the objective function,and the radial basis function has a better fit and prediction accuracy for the complex nonlinear function.Based on this,this thesis proposes an optimization process based on feedback,which can achieve the best prediction accuracy of the optimal value within a limited number of sampling times.For the key problems in the multi-material collaborative optimization,this paper proposes an effective solution.Using material coding mapping,the material variables are incorporated into the multi-objective optimization process.Through the postprocessing of the experimental matrix,DOE design that includes both continuous and discrete variables is achieved.Finally,the material cost control problem is derived through the example of the flat plate model.The solution of the custom external function is proposed and verified.This article uses the finite element method to analyze the performance of the liftgate initial structure.To ensure the accuracy of the finite element model,the modeling method is standardized from meshing,connection,quality,etc.Second,according to an enterprise standard,modal analysis,stiffness analysis,and oil-canning analysis are conducted to obtain the initial performance of liftgate.On this basis,this thesis uses topological optimization methods to obtain the scheme of tailored welded plates design,and uses the main effect method and variance analysis method to comprehensively filter the variables.Finally,through the multiobjective optimization method based on feedback,the thickness-material collaborative lightweight design with low cost and good mechanical performance is achieved,and a reference example is provided for the same type of planning.The multi-objective optimization method proposed in this thesis provides a solution for the complex nonlinear optimization problem that contains both continuous and discrete variables,and achieves the collaborative multi-objective optimization of liftgate material types and plate thickness.It provides theoretical guidance and practical application value for the development of multi-material automotive lightweight technology.