Precise Neck Modeling Based On Injury Biomechanics And Its Application In Low-speed Rear-end Collision

Seat belts and airbags protect the head and chest of passengers well in low-speed rear-end impact, the neck is easily to be hurt with the impact of acceleration, neck injury has been the most common damage in low-speed rear-end car collision. According to statistics of Japanese Compulsory Automobile Liability Insurance, nearly eighty percent of damage in rear-end collision was neck injury, forty-nine point four percent of neck injury was account for rear-end collision in all kinds of collision. Therefore, the in-depth study of the biomechanical responses and injury mechanism of neck tissues in rear-end collision is of vita practical significance for the design of vehicle safety.A biomechanics model of neck for 50 th percentile Chinese adult man with high precision was developed based on whole neck anatomical structure. The model consists of vertebrae(compact bone and cancellous bone) and intervertebral disc(fiber ring, nucleus pulposus and cartilage endplate), ligaments, joints and muscles. Different material properties were defined for the neck tissues based on the biomechanical characteristic of tissues and related references, and the atlanto-occipital joint and capsular ligament was built to connect the neck model and existing head model.The biomechanical model was evaluated based on the cadaver head-neck drop test, rearend impact of volunteers and 20km/h hard brake test of four 50 th percentile Chinese male volunteers. The results showed that model had high level of biofidelity, can accurately reflect biomechanical response of 50 percentile male of Chinese more. Acceleration curve of vehicle in low-speed rear-end impact collected by Maria Krafft were used in the simulation, analyze dynamic response of head-neck and biomechanical response of neck tissues. The phenomena of the S-shaped and C-shaped of cervical appeared successively in low-speed rear-end impact, and the neck was most likely injuried in S-shape and C-shape, especially lower vertebrae C7 and T1, intervertebral discs and facet joints near C7~T1 were most likely injured.Through compared stress value of neck tissues in simulations with different rate of change of velocity, founded that injury occurr ed in different tissues with the different rate of change of velocity in rear-end collision, the injury will bring down with the lower peak value of vehicle acceleration in collision. Analyze the effect of distance between headrest and head, the stiffness of headrest and with or without headrest on neck injury, the results indicated that headrest can protect the passengers’ neck well in rear-end compact, decreased the distance between head and headrest or lower the stiffness of headrest can reduce neck injury in rear-end collision. The biomechanical modeling of neck and simulation analysis can provide important significance to the study of protective measures of neck and the rule-making of automobile standard regulations and independent development design of new model car.