Research On Lightweight Design Method Of Engine Hood Based On Pedestrian Protection

With the rise of the number of automobile, environmental pollution and energy shortageis increasingly prominent, major automobile enterprises urgently need to develop and productenergy-saving and emission reduction cars in order to adapt the development of futureautomobiles. The research indicated that, every10%reduction of the auto weight energyconsumption will be reduced by10%and the exhaust emissions will be reduced by5%to6%.Therefore, automobile lightweight is one of the effective paths to deal with environmental andenergy issues. However, lightweight can’t take sacrificing the safety as a price. During thelightweight design process, the security must be taken as an important target. Automobilebody as an important component of a car, it plays a key role for the lightweight of a wholevehicle.Therefore, to choose suitable structure and matreial and consider the crashworthinessfor vehicle body during design stage is of great significance to improve the performance ofthe car and shorten the design cycles.This paper took engine hood as the research subject and made a detailed introduction tothe multi-objective topology optinization which was the key technology in the structuredesign of automobile body, and then extracted the bending rigidity, torsional rigidity andmodal properties.We got the topology of the engine hood through topology optimizationdesign in static load conditions and checked static performance of the reconstruction model.Considering the impact of engine hood during the collision process we took the Head Injuryas its security evaluation to verify the topology structure design meet the requirements or notand redesigned the structure that did not meet the requirements.In view of the design marginof engine hood, this paper took its thickness as variable and took the mass, the modal and theHead Injury as responses to set up approximation model and use Non-Dominated SortingGenetic Algorithm to obtain the optimal thickness in order to enable the engine hood to meetlightweight and security requirements meanwhile.Finally, we discussed another lightweightdesign method of using aluminum alloy materials and innovatively proposed a new type ofmaterial splicing engine hood.The results showed that: The multi-objective topology optimization avoided the optimalsolution of single objective topology optimization without convergence and could obtainreasonable topology;In the early phase of conceptual design involved the research ofpedestrian protection could enhance the safety performance and shorten the design cycle;Theoptimal solution through approximation model and NSGA-Ⅱmade engine hood meet thelightweight requirement and balance between rigidity and safety performance; Material splicing engine hood was a good solution to the high cost of aluminum alloy inner plate.This study provides some reference for the domestic automotive enterprises to carry outthe lightweight design work, and opens up a new way of solving the issues of environment,energy and automotive safety.