Design optimisation of passenger car hood panels for improved pedestrian protection

This article presents research motivated by the prospect of imminent implementation of the new regulatory requirement for pedestrian protection GTR9 (Global Technical Regulation9). A new methodology has been developed for optimisation of the hood panel of passenger cars to ensure that the pedestrian Head Injury Criterion (HIC) falls below the threshold values specified by both the GTR9 and the consumer metric, the Australian New Car Assessment Program (ANCAP). To meet the performance criteria for pedestrian protection head impact, it is vital to incorporate the associated design parameters into the hood design process at an early stage. These parameters are architectural in nature whereby changing them later in the vehicle design process would be very expensive and difficult to implement. The developed methodology for the design of a hood configuration aims to provide a robust and homogeneous HIC for different impact positions in the central area of the hood of a large sedan, taking into consideration the limited space available for deformation. The non-linear Finite Element Analysis (FEA) software LS-DYNA was used in this research to simulate the GTR-9/ANCAP pedestrian head impact testing procedures. The efficiency of a hood design was calculated as the ratio of the theoretical optimal deformation of hood assembly for a given value of HIC to the actual deformation calculated for the same HIC value of the corresponding numerical test. The efficiency and HIC value were derived for each configuration and compared to obtain the optimal solution for homogeneous performance and minimal deformation of outer and inner hood panels. The Kriging response surface and the Monte Carlo method were used in the design of numerical experiments. The outcomes of this study provide a clear indication that an optimum configuration of the hood panel of a passenger car can be developed to minimize the hood deformation while meeting the requirement for HIC value.