The Study Of Lightweight Method Based On The Vehicle Body Structure

With the rapid growth of car numbers, the global problem of resourcesdeficiency and environmental pollution is becoming more and more prominent. Thelightweight of cars is one of the most valid means to solve the problem. The car is acontradictory product, which is composed by a variety of performance. In order tomeet the demand of automotive various performances, other car’s performance (suchas power, safety and comfort, etc.) should be guaranteed not to drop with executingthe lightweight for car. In this paper, the study of automobile body structurelightweight methods is mainly from two aspects: the application of new lightweightmaterial and the optimization of automobile body structure design. The following arethe main study content.1) Taking the hood, which is a closed component of the body in white, as aninstance, the topology optimization about car body structure with the satisficingtrade-off method is researched. According to SIMP (solid isotropic material withpenalization) and satisficing trade-off method, a multi-objective topologyoptimization way is presented combined with OPTISTRUCT software. The inequalityconstraint condition which is included only in satisficing trade-off method is avoideddirectly via certain transformation approach. At the same time, In the process ofoptimization, with average characteristic frequency formula as the objective functionto optimize the first three natural frequencies, guarantee that the phenomenon ofmutual exchange order between the first three natural frequencies won’t occur. Afteroptimizing the hood, its torsional rigidity and three natural frequencies have improvedsignificantly with quality becomes lighter. What’s more, it’s bending stiffness withinthe permission scope.2) Taking the above hood optimized as an instance, the application of compositematerials in a car body structure is researched. The T300/5280carbon fiber reinforcedcomposite materials (with T300fiber and5208epoxy matrix) is applied to theexternal panel of hood. After optimize both the thickness of the internal panel of hoodand the thickness and the angle of composite layer, the optimization goal should be as follows: Making the target performance of the hood (bending rigidity, torsionalrigidity and modal properties) be further improved in the case of the quality of hoodreduced by at least15%, the composite materials without failure and other steelmaterials without yield in the static condition.3) Taking the front door, which is a closed component of the body in white, as aninstance, a Multidisciplinary design optimization method that considers both theoptimality problems and the robustness problems (the response to the controllablefactor fluctuation) of the car body structure multi-response is proposed. In this paper,two working conditions of the vehicle door that the first natural frequency and theside impact are considered. The entire car’s collision model is simplified to improvethe design efficiency. The approximate mathematical model for each response isderived by Latin Hypercube experimental design and response surface method, andon this basis, the model of the overall multidisciplinary optimization is built includingoptimization and robustness. At last, the overall multidisciplinary optimization issolved with the genetic algorithms. After optimization, the weight of the door getsreduced, and the optimality of all responses (the first natural frequency, the energyabsorption of the door anti-collision bar, and the intrusion displacement of the cardoor internal panel) and the robustness of vehicle door structure are improved.