Finite Element Simulation And Lightweight Design Of A Passenger Car Body-in-White

As China’s car ownership is increasing year by year,low-carbon environmental protection has become a new challenge.Automobile lightweight has been regarded as a key core technology to effectively solve the problems of energy consumption and environmental pollution.At the same time,with the upgrading of computer hardware facilities,finite element simulation technology has become an indispensable tool in the research and development of body products.Therefore,the main research content of this project is to use finite element numerical simulation technology to take the body-in-white of a passenger car as the research object to analyze the structural performance,screen the design variables by sensitivity analysis method,combine the experimental design sampling data as the input matrix of the approximate model,and replace the actual model with the constructed approximate model for multi-objective optimization.The specific research work mainly includes the following aspects:Firstly,following the equivalent principle of body mechanical properties,the geometric model is simplified.The structural parts are meshed according to the grid standard and the finite element model of the white body is built by welding.According to the finite element model of the built body-in-white,the free modal analysis is carried out.According to the evaluation method and evaluation standard of the bending stiffness and torsional stiffness of the body-in-white,the torsional stiffness,bending stiffness and the change trend of the longitudinal stiffness along the body are calculated respectively.Secondly,based on the stiffness and modal characteristics of the body-in-white structure,the sensitivity analysis principle is used to calculate the direct sensitivity value,and 74 parts that need to be optimized are preliminarily screened.In order to comprehensively consider the influence of thickness change on plate quality and other properties,the concept of relative sensitivity analysis is introduced.Finally,the relative sensitivity data results of each performance are used to screen 15 optimization design variables and select the output response to increase or reduce the thickness of the parts in the body model to determine the optimization direction.In addition,by comparing and analyzing the characteristics of different experimental design methods and the corresponding simulation times,the extensible grid sequence method was finally selected to collect 150 sample data with 15 sets of design variables as the analysis objects.In order to select the approximate model with the highest accuracy,the error and accuracy of various approximate models are compared.After comparative analysis,the Kriging fitting approximate model is finally selected to replace the direct simulation calculation for subsequent optimization design.Finally,the optimal solution set is selected by comparing the Pareto optimization effect of the global response surface method and the multi-objective genetic algorithm.Finally,a set of optimal solutions are selected and adjusted according to the actual needs,and the performance indexes of the original body model and the optimized body model are compared.It is found that the optimized natural frequencies of each order are improved.Among them,the first-order torsional modal frequency value is increased by 0.84 Hz,and the first-order bending modal frequency value is increased by 3.18 Hz.The mass is reduced by 3.14 kg compared with the original model.The bending stiffness is increased by 426N/mm and meets the expected value requirements.The torsional stiffness is reduced by 136N·m/deg compared with the original model.Although it is slightly reduced,it is still within the scope of the body design requirements,reaching the purpose of the lightweight research of this topic.