Optimization Design Of Hood Inner Based On Pedestrian Head Protection And Stiffness Requirements

With the increasing of automobiles in China, injuries of the vulnerablepedestrian in car accidents are raising. Head injury is the main cause ofpedestrian deaths. In car-pedestrian accidents, engine hood is the main contactarea with pedestrian head. Hence, carrying out research of hood optimizationdesign based on reducing pedestrian head injury is of great significance.Besides, the hood design needs to satisfy the torsion and bending stiffnessrequirements in different working conditions.Most of the existing research of hood optimization design is to purelyimprove pedestrian head protection performance or static stiffness. These twodesign objectives are dealt with separately and independently. At present,there is a lack of an efficient way that can combine these two kinds of designrequirements simultaneously in vehicle hood optimization process.Accordingly, this paper proposes a multidisciplinary design optimizationmethod for hood inner based on the coupling of pedestrian head protectionand stiffness requirements. Due to that a hood is more likely to cause harm onchildren, this paper mainly focus on the analysis of child headform impactwith a hood.Firstly, according to the requirements of GB/T24550-2009, an FE modelof child headform impactor is developed based on LS-DYNA software. Theregulation requirements of head mass, centroid and moment of inertia are satisfied by defining the key geometric parameters. Making use of responsesurface optimization method, key material parameters are defined to meet thedrop acceleration and frequency requirements. The verification of childheadform FE model shows that this model meets the regulation requirements.This child headform FE model is used for follow-up research on childpedestrian protection.Commercial CAE software LS-DYNA, MSC NASTRAN andENKIBONNET are selected as the tools for impact simulation, stiffnessanalysis and parameter optimization respectively. Using the child headformFE model developed, pedestrian head impact and static stiffness of a specifichood are analyzed. The hood parametric design and optimization are carriedout based on coupling of pedestrian head protection and static stiffnessrequirements. After the construction of simulation model, impact and stiffnessperformance are analyzed. Optimal design solution is obtained by turning thehood inner optimization into CAE parametric design, in which responsesurface method and genetic algorithm are used to determine the optimalparameters. Optimization solution significantly achieves better headprotection effect, which validates the feasibility of this proposedmultidisciplinary optimization method and provides reference approach foroptimal design of engine hood inner.Finally, the forward conceptual design of an aluminum hood innerstructure is conducted. A design solution of hood inner structure is exploredon the basis of one particular hood skin. The pedestrian head protectionperformance of this aluminum hood is assessed. Afterwards, comparativeanalysis on the head impact performance of the aluminum and a steel hoodare implemented. This kind of design method may give some guidance forhood inner structure forward design and development.