| In recent years,with the increasingly prominent energy crisis and the enhancement of people’s awareness of environmental protection,all countries in the world are vigorously developing electric vehicles.However,in the current battery technology background,the range of electric vehicles has been criticized.It is an efficient technical means to improve the range of electric vehicles by lightweight design of electric vehicles.As the best automotive material,composite materials can be applied to the lightweight design of automobiles to improve the lightweight of the vehicle more effectively.As a key component of the electric vehicle battery system,the battery box has a direct impact on the safety,handling stability and comfort of the vehicle.This paper relies on the national key research and development program to complete the lightweight design of battery box for a certain electric vehicle,the main research contents and conclusions are as follows:Firstly,the physical model of the battery box of a certain model is measured,the relevant parameters of the model are obtained,and then the three-dimensional model of the battery box is established in the CATIA software.Then,the three-dimensional model is meshed in the Hypermesh software,and the model attributes and connection relationships are given to complete the finite element modeling of the battery box.Secondly,referring to the relevant literature at home and abroad,and discussing with the original equipment manufacturer,the load condition of battery box is determined as follows: bumping road turning conditions,bumping road brake conditions,random vibration analysis,modal analysis and extrusion analysis.Then the battery box is simulated,and the performance of the battery box under various working conditions is evaluated,which provides a reference for future optimization design.Thirdly,because the main functions of the upper and lower boxes are different,different optimization schemes are adopted for them.The upper box is not used as the main carrier,so the shape optimization is used to improve the modal frequency,and then the size optimization technology is used to determine the best thickness of the upper box.After optimization,its thickness is reduced from 3mm to 2mm.Then,the lower case is used as the main carrier of the battery box.For the deeper weight reduction,the optimization scheme of replacing the original aluminum alloy material with carbon fiber is adopted.The free-size optimization technique is used to determine the layup area of carbon fiber layups at different angles,and then the size optimization technique is used to determine the layup thickness of the layers at different angles.Subsequently,the multi-objective optimization of the lower case of carbon fiber battery box is completed by establishing an approximate model.The goal of multi-objective optimization is to maximize the first-order modal frequency and the minimum mass of the battery box.The response of other operating conditions is used as a constraint to determine the thickness of the battery box lug and the thickness of the carbon fiber layer at different angles.Next,the order of carbon fiber layup is optimized while considering the manufacturing constraints.Finally,according to the optimization results,the battery box is re-modeled,and the performance of the optimized battery box is analyzed to verify the rationality and feasibility of multi-objective optimization.The simulation results show that the lightweight battery box meets the requirements of various working conditions.The first-order modal frequency is increased from 20.67 Hz to 30.63Hz;the maximum displacement of lateral extrusion is reduced from 23.76 mm to 7.19 mm,the maximum displacement of longitudinal extrusion is reduced from 10.39 mm to 4.68mm;the quality of the battery box is reduced by 29.8%. |
