Optimization of Head Impact Waveform to Minimize HIC

To mitigate head impact injuries of vehicle occupants in impact accidents, the FMVSS 201 requires padding of vehicle interior so that under the free-moving-head-form impact, the head injury criterion (HIC) is below the limit. More recently, pedestrian head impact on the vehicle bonnet has been a subject being studied and regulated as requirements to the automobile manufacturers.

Over the years, the square wave has been considered as the best waveform for head impacts, although it is impractical to achieve. This paper revisits the head impact topic and challenges the optimality of aiming at the square waveform. It studies several different simple waveforms, with the objective to achieve minimal HIC or minimal crush space required in head-form impacts. With that it is found that many other waveforms can be more efficient and more practical than the square wave, especially for the pedestrian impact. It presents a theoretically most efficient waveform and some more practical ones, such as the modified “optimal” waveform and ramp-down triangle waveforms. These waveforms are frequently encountered in the pedestrian head-form impact on the bonnet, and trying to achieve a square wave in this case can be misguiding.