Influence Of Neck Muscle Activation On Head-neck Response During Pedestrian Accidents

As a vulnerable group in traffic,pedestrians are involved in a large number of traffic accidents.Most of the existing human models cannot simulate the active response of muscles in real situations,and cannot reasonably present the head and neck injuries in pedestrian accidents.This paper focuses on the influence of neck muscle activation on the head and neck response of pedestrians.Based on HBM-Head-Neck FE Model and HBM-Head FE Model,a new hybrid finite element model of human head-neck with detailed neck muscles,cervical spinal cord and human brain was developed.After being validated under front impact and lateral impact,the head-neck model was coupled with the body of the LSTC pedestrian model.The validated hybrid pedestrian model was then used to study the effect of neck muscle active contraction on pedestrian head-neck response.Four kinds of impact velocities(20km/h,30km/h,40km/h and 50km/h)and two kinds of pedestrian gaits(Struck Leg Backward and Struck Leg Forward)are considered in this paper.It is found that neck muscle active contraction can reduce the neck bending amplitude and head rotation acceleration peak value before head hits the windshield,but increase both translation acceleration peak value and rotation acceleration peak value of head when head hits the windshield,and increase head HIC value.In terms of injury,neck muscle active contraction increases the risk of head injury,but has no obvious effect on neck injury.Such influence is obvious especially under low-speed collision with SLB gait.In addition,the risk of head injury with SLB gait is higher than that with SLF gait,but the risk of neck injury is lower.The injury difference between these two gaits decreases with the increase of collision speed.Stress distributions of pedestrian head and neck tissues are also analyzed in this paper.The injury of skull and cervical spine is obviously related to both compression stress and shear stress.Craniocerebral soft tissue injury is mainly caused by compression stress.The annulus fibrosus of intervertebral disc is obviously affected by shear stress,while the nucleus pulposus is mainly squeezed.Both compression stress and shear stress are more obvious in spinal cord gray matter than that in white matter,indicating that gray matter is more vulnerable than white matter.