M. Tanaka, H. Yoshida, and S. Tsutsumi (Japan)
FEM Modeling, Biomechanical Simulators, Cervical Model, Whiplash Injury
vehicle accidents in Japan . Though the death rate is low in these type of accidents, the minor injury rate is almost 90 percent with most injuries being neck injuries so-called "whiplash injury" which occur often in these low-speed rear-end collisions. In the year 2000, 530,000 people suffered from neck injuries and insurance payments amount to 3.0 billion dollars (equal to 350 billion yen) a year in Japan. The mechanism of whiplash injuries is not yet fully understood. To investigate the mechanism of whiplash injuries in low-speed rear-end collisions, two analyses were conducted. Although there have been many attempts to clarify the mechanism of whiplash injuries recently, the mechanism is still not fully understood. This is because it is difficult to reproduce actual rear-end automobile accidents in research test. To solve this problem, we conducted experimental and numerical analyses. First, we developed a new biomechanical cervical model named the "K-D neck model" to reproduce human neck movements in low-speed rear-end collisions. Shear displacements were observed in the plane of the intervertebral disks. Secondly, to verify the biomechanical fidelity of the K-D neck model, numerical analyses using finite element models with both active and passive muscle elements were conducted to compare each lateral head displacement of a cadaver, a volunteer and the K-D neck model. To reduce whiplash injuries, a car seat equipped with a new headrestraint system was developed. The headrestraint swings forward during low-speed rear-end collisions. Through sled tests, we measured the neck's lateral and longitudinal cervical movements every 1 millisecond (msec), and observed that the faster support of the dummy head was effective in reducing both lateral and longitudinal displacements between each cervical vertebra. 1. Experimental analyses with the new biomechanical cervical model (named the K-D Neck Model) 2. Numerical analyses with a finite element method (FEM) 2. NECK MODEL 2.1 NECK MODEL COFIGURATIONS The neck of the human body (Figure 1.) is composed of cervical vertebrae, ligaments, intervertebral disks, muscles and other items.
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