Optimisation of hood panels of a passenger car for pedestrian protection
Creators: name: Krishnamoorthy, Revathi
Publisher: name: RMIT University
Year: 2024

description: This thesis presents a pro–active research work motivated by the prospect of the imminent implementation of the regulatory requirement for pedestrian protection, Global Technical Regulation–9 (GTR–9) (United Nations Economic Commission for Europe 1998) in the near future. To meet the performance criteria for pedestrian protection head impact, it is vital to incorporate the required design parameters into the hood design process at an early stage. These main design parameters are architectural and changing them late in the vehicle design process is very expensive and difficult to implement. The main design parameters are the inner and outer hood thickness, inner and outer hood material, inner hood structure and the available deformation space to hard components such as the engine.<br><br>The main objective of this work is to develop a methodology for optimising hood panels of passenger cars to ensure that the pedestrian Head Injury Criterion (HIC) falls below the threshold values specified by both the GTR–9 and the consumer metric, the Australasian New Car Assessment Program (ANCAP). This study investigated the development of a hood configuration that provides robust and homogeneous HIC for different impact positions in the central area of the hood of a large sedan, taking into consideration of the limited space available for deformation. <br><br>An extensive series of Computer Aided Engineering (CAE) simulations has been carried out to collect the acceleration data and vertical intrusion data required to validate the proposed methodology and the optimal hood configuration. These impact simulations include a stationary vehicle set up and a moving head impactor as per GTR–9. The Design of Experiments (DOE) has been set up with the control factors as inputs to the Kriging response surface and Monte Carlo methods to output the responses. The variables considered for the control factors are the inner hood structure, inner hood thickness and material, outer hood thickness and material, and the impact positions. The results from the numerical tests have been utilised to map the response surfaces in order to identify the important variables and to visualise the relationships between the inputs and the outputs.<br><br>The proposed optimisation methodology is described in detail and the outcomes provide clear recommendation of the optimal configuration of passenger car hood panels. <br><br>In conclusion, if the vehicle design team’s main objective were to reduce the deformation space, the preferred choice for hood material would be steel rather than aluminium. The benefits of minimising the deformation space are significant. They include the freedom of styling, improved aerodynamics, and hence improvements in vehicle stability and fuel economy. The trade–off will be a higher mass than the equivalent aluminium system. On the other hand, if the vehicle design and program team’s main objective was to reduce the system mass, then the preferred choice for hood material would be aluminium. The trade–off would be a higher deformation space than that is required for the steel system.<br>