Frontal impacts involving passenger cars account for a large number of occupant fatalities and injuries throughout the world. Many of these fatalities could have been avoided with better crash compatibility, i.e. better structural interaction and the matching of front stiffness characteristics in car-to-car collisions. Also, many of the injuries occurring in frontal impacts, especially low severity injuries, might have been mitigated with crash pulses that better utilises the available deformation of the vehicle front. Previous studies have consistently suggested that the best crash pulse shape includes an initially high deceleration followed by lower deceleration, which is quite different from the progressively increasing crash pulses that can often be seen in real-world collisions. This thesis proposes adaptive vehicle frontal structures to address the problem of stiffness incompatibility and to promote the crash pulses that have been suggested as optimal from an occupant restraint loading and injury reducing point of view. The work features mass-spring models for an early estimate of the injury risk reducing effect of adaptive frontal structures, finite element modelling for detailed analyses of the energy absorption of frontal structures, and occupant modelling for examining the effect on occupant kinematics of different crash pulse shapes. Results suggest that an initially high deceleration or a constant deceleration is preferable compared to a progressively increasing pulse. However, finite element simulations suggest that modification of a single front component might not be sufficient for changing crash pulse characteristics. Future passenger cars should adapt to each crash scenario by altering the force levels in global load paths, and thereby contribute to better overall passive safety. (Author/publisher)
Samenvatting