Effects of the Body and Seatbelt Design on Occupant Impact in Car Crash

In the automobile frontal collision, the maximum value of the chest deceleration is one of the most important performance indexes for the occupant protection, and depends on the time history of the car deceleration. Therefore, it is important to analyze the relationship between the chest and car deceleration, and find the car crash characteristic which causes the minimum chest deceleration. In the most research, 2 DOF model (car and occupant) at translation motion was generally used. However, it is difficult to understand an occupant impact because a real occupant is restrained by the shoulder and lap seatbelt and the upper body has rotational motion during a collision. In this paper, the relationship between the chest and car deceleration were analyzed by 4 DOF model taking into consideration its rotation. Moreover the effect of a force limiter of a seatbelt was also examined. Based on the theoretical and experimental results, we derived the knowledge for an optimum automotive crash design.