A design optimization approach of vehicle hood for pedestrian protection

Abstract

Head injuries are the most common cause of fatality in vehicle-to-pedestrian collisions. To reduce the incidence and severity of such injuries, subsystem tests are used in which headform impactors are impacted upon the vehicle hood. The development and validation of an adult headform impactor finite element (FE) model are presented in the study. The geometry was obtained from a drawing of a physical headform while the skin material model was modeled as viscoelastic material with parameters identified by FE optimization to match quasi-static and dynamic test data reported in literature. Overall, it was shown that the geometrical and inertial characteristics of the headform FE model developed in this study satisfy compliance and certification regulations. Then, the results from a hood design optimization using simulations of a headform-to-hood impact test are presented. The baseline design was a generic hood design consisting of two plates connected by buckling structures. Minimization of the underhood clearance space subjected to the admissible limit of head injury risk under impact as constraint was included in an optimization problem. The automated design process, which considered the geometry of connecting spools and the panel thicknesses as design variables converged to an optimum design after several iterations. The methodology and recommendations presented in this paper may assist in the hood design of new vehicle models to reduce pedestrian head injuries and meet new safety requirements.