Multi-Objective Optimization Of Car Body

Lightweight of automobiles is an important factor to respond to the national policy of energy saving and reduction of exhaust gas.Its main purpose is to reduce energy consumption by reducing the mass of the car.In addition,traditional lightweighting is simply a single optimization goal that optimizes the quality of objects and sometimes has to abandon some of its aesthetic performance,resulting in reduced reliability.Therefore,based on multi-objective optimization,this paper focuses on both the vehicle body mass and torsion stiffness as the optimization purpose.The main work and conclusions are:1.The finite element model of car body is established.The static strength of car body under torsion,bending,braking and turning conditions is analyzed.The stress and displacement of dangerous parts of car body under four working conditions are obtained.The results show that the car body meets the requirements of strength and stiffness.2.The free modal analysis of car body finite element model is carried out;Through the evaluation and comparison method,it is determined that the natural frequency of the car body is far greater than the external excitation generated in the driving process,and there will be no resonance.3.Based on the sensitivity analysis method and the torsion mass relative sensitivity theory,15 design variables of multi-objective optimization are determined;Based on Latin hypercube sampling method,the response functions of car body mass,torsion displacement,torsion stress,bending displacement and bending stress are established;Taking the car body mass and torsion displacement as optimization objectives,taking the body torsion stress,bending displacement and bending stress as constraint functions,the multi-objective optimization model of car body is established.Finally,the multi-objective optimization of car body is carried out based on multi-objective genetic algorithm.Compared with the structure before and after optimization,the weight of the whole vehicle is reduced by 5.3%,the bending stiffness is increased by 6.9%,the torsion stiffness is increased by 10.0%,the maximum bending stress is reduced by 14.4%,and the maximum torsion stress is reduced by 9.1%.It not only achieves the purpose of lightweight,but also improves the mechanical properties of car body.