A Methodology Using a Combined Injury Criteria Index to Study the Performance of Various Driver Restraint System Configurations

The objective of this study was to evaluate the performance of various configurations of a driver restraint system by using a combined injury criteria index and making the restraint system adaptive to different frontal crash coinditions, such as severity of the crash, belt use, sitting position, pre-impact braking and size of the driver. For this purpose, a mathematical model of a driver restraint system was developed. The study was divided into three steps: 1. A FE-model of the driver airbag was developed by using MADYMO 3D program; 2. The model was validated by comparing the simulations to crash tests; 3. Effects of design changes in an adaptive restraint system on injury parameters were investigated in simulations of frontal car impacts. It was found that the performance of the restraint system was most influenced by the size of the ventilation hole and the capacity of the gas generator. The best performance of an airbag for an unbelted 50 and 95 dummy can be achieved by choosing a relatively large vent hole diameter in combination with a high mass flow at impact speeds of 48 km/h or higher. For a 5 dummy, a lower level of gas generator was preferable at 25 km/h while a higher performance of the gas generator was desirable at 48 km/h. These effects interfered with the effects of other variables such as the seat belt system including a pretensioner, load limiter. A complete restraint system has to be tuned together to achieve the maximum safety performance. It is preferable, in terms of injury parameters, to absorb the kinetic energy of the belted dummy with the maximum allowable motion. This can be achieved with a lower force level in the load limiter.