Citation

Kitagawa Y, Yasuki T, Hasegawa J. Proc. IRCOBI 2008; 36: 381-396.

Copyright

(Copyright © 2008, International Research Council on Biomechanics of Injury)

DOI

unavailable

PMID

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Abstract

According to the traffic accident data in Japan, the number of rear impacts is the largest among the various car crash scenarios on the road. Neck injury due to low speed rear impacts continues to be a significant issue in terms of social cost. Although the precise injury mechanism is still not determined clearly, it is commonly recognized that a relative motion between the head and torso could be one of the factors causing the injury. Neck injury criteria (NIC) and some other indicators have been developed to assess injury risk and some are used in laboratory tests. Recent studies focus on the joint capsules as a potential site of neck pain. Experiments were conducted to evaluate joint capsule strain under simulated loading conditions. Various seat systems have been developed aiming to help reduce the injury risk. There have been two approaches used in reducing the relative motion between the head and torso. One is to allow the occupant torso to sink into the seat-back, and the other is to support the head as early as possible. The second approach has led to the development of active head restraint systems. The active head restraint system is designed to move the head restraint forward (closer to the occupant's head) when activated in rear impacts. The effectiveness of such systems is verified evaluating the dummy readings (indicator values) and sometimes investigating the field data. The authors previously conducted a study using a human body finite element (FE) model to estimate the effectiveness of a fixed head restraint system in terms of both NIC and Joint Capsule Strain. The results confirmed that seat design factors such as the forward location of the head restraint could help lower the indicator values. This study investigates the effectiveness of the active head restraint system in reducing both NIC and Joint Capsule Strain. A human FE model is used to simulate the occupant head and neck motion with the different head restraint systems. The study also analyzes the cervical vertebral motions to investigate the function of the active head restraint system in correlation with the strain growth in the joint capsules.