Biw Lightweight Research Of A Electric Car Based On Relative Sensitivity

The car body is a complex structure composed of a large number of parts,which is an important part of the vehicle.The lightweight design of car body can significantly reduce the weight of the vehicle,so that the performance of the vehicle is improved,thereby reducing the increasingly serious energy depletion and environmental pollution problems.The BIW not only can solve some energy and environmental problems,but also it can extend the cruising mileage of pure electric vehicles.In order to implement the principle of sustainable development,the pure electric vehicle body lightweight design is an important issue in the modern automotive industry.At present,there are three main methods of the lightweight of automobile:structural optimization,the use of new materials,the use of new manufacturing technology.In this paper,a domestic pure electric vehicle is served as the research object.The car body of the lightweight design is based on the theory of finite element analysis with the use of structural optimization.The torsional stiffness is optimized by improving the process and modifying the structure.The main contents of this paper are as follows:(1)The finite element model of white body was established by using Hypermesh.The white body of the electric car is composed of a large number of complex sheet metal parts and cover pieces.In order to establish a precise and appropriate finite element model,this paper has studied and summarized the establishment principle and establishment method of the finite element model.In accordance with certain principles to clean up the white body of the geometric model,select the appropriate cell size for the grid,and then select the appropriate solder joints and vest the properties of the components,the finite element model of car body is established.(2)The static and dynamic stiffness of the vehicle body is analyzed.The calculation principle and method of bending stiffness and torsional stiffness are expounded.The calculated results are analyzed according to certain evaluation criteria.It is found that the body has good bending rigidity,but the torsional rigidity is insufficient,which is the important direction of post-structure optimization.The modal frequency and the transducer type of the body are analyzed.The results show that the vehicle has good dynamic stiffness performance,and the resonance problem would not occur when the vehicle is running normally.And the emergency braking condition and cornering condition of the car body are analyzed.(3)The influence of the thickness of the body parts on the performance of the vehicle is explored.The principle of sensitivity optimization method is stated.the thickness of 100 body parts is chosen as the design variable,and the sensitivity of the thickness of these parts to the bending stiffness,torsional stiffness,first order mode frequency and vehicle weight are analyzed.The results show that sensitivity analysis does not provide a good design for lightweight.So other evaluation criteria are needed.(4)BIW lightweight design of A electric car based on relative sensitivity.Direct sensitivity analysis can not find the key lightweight design variables.With the study of the relative sensitivity of the analysis of the same time on the stiffness and quality of the high sensitivity of the components,ultimately 30 parts were identified as the design variables.And then imposing the constraints and setting the minimum quality of the body as the goal,the paper calculated the structure of BIW.The results were compared with the original comparison,and it is founded that the bending rigidity decreases slightly,the torsional rigidity increases,and the car body mass decreases.Then the torsional rigidity of the car body was optimized,and the torsional rigidity was raised to the level of the same class car by using process improvement and structural modification.