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Impact severity is a fundamental measure for all in-depth crash investigation projects. One methodology used in the UK is based on the US Calspan software package CRASH3. The UK- in-depth crash investigation studies routinely use AiDamage3 a software package which is based on an updated version of the original CRASH3 algorithm, including enhancements to the vehicle stiffness coefficients. Real world accident-damaged vehicles are measured and their crush is correlated with a library of stiffness coefficients. These measurements are then used, along with other parameters, to calculate the crash energy and equivalent changes of velocity of the vehicles (delta-v), which is a measure of the impact severity. UK in-depth accident studies routinely validate the crash severity methodologies applied as the vehicle fleet changes. This is achieved by analysing crash test data and using the appropriate residual crush damage and other inputs to AiDamage3 and checking the program- outputs with the known crash severity parameters. This procedure checks, at least in part, the default stiffness values in the data libraries and the reconstruction methods used.
In spite of today's highly sophisticated crash test procedures like the different NCAP programs running world-wide, bad real world crash performance of cars is still an issue. There are crash situations which are not sufficiently represented by actual test configurations. This is especially true for car to car, as well as for car to object impacts. The paper describes reasons for this bad performance. The reasons are in principal bad structural interaction between the car and its impact partners (geometric incompatibility), unadjusted front end stiffness (stiffness incompatibility) and collapse of passenger compartments. To show the efficiency of improving cars' structural behaviour in accidents with different impact partners an accident data analysis has been taken out by members of European Project VC-COMPAT. Accident data analysis has shown that in Germany between 15,000 and 20,000 of the now severely injured car occupants might get less injured and between 600 and 900 car occupant fatalities might be saved. Similar results arise for the UK.
This study investigates the protection offered by passive head-restraints with different stiffness and energy dissipation properties. For this purpose, computational multi-body models of a generic car seat and a biofidelic 50thpercentile male human for rear impact are used to study different seat designs and passive head-restraints. The validated seat-occupant model is also used in the design of two different car-seat models which are shown to effectively mitigate whiplash by utilising a crash-energy distribution technique. Five different passive head-restraints with varying stiffness (low-medium-high) and energy dissipation percentages (low-high) are successively attached to four different car-seat models. The simulation results indicate that the protection offered by head restraints is strongly dependent on the seat design. It has also been shown that the stiffness of the passive head-restraint has much more influence on whiplash-risk in comparison to its energy dissipation capacity.