Investigation Of Injury Assessment Using Six-year-old Child Finite Element Model As Specified In C-NCAP (2021)

In recent decades,the research on the adult’s injury mechanisms caused by the traffic accidents has been made great progresses.The severity of adult injury has been reduced by optimizing the automobile body structure and developing the passive safety devices,but the research on the injury of child occupant is very limited.Children are not scale adults because their bones and soft tissues are growing with the age.So that the differences of physiological structure characteristics inducted the injury mechanisms and tolerance.The injury mechanisms of children need to be deeply studied and analyzed based on children’s characteristics.In this study,the injury mechanisms were investigated and analyzed in-depth using the biomechanical computational models of six-year-old child occupant with detailed physiological structure characteristics.The results will be great significance and application value to study of child occupant injury mechanism and protection.The sitting posture will be diversity on account of the children’s behavior and the development of the intelligent cockpit in the future.Therefore,this finite element models were constructed with 120°and 135°sitting posture respectively based on the 105°sitting posture model of six-year-old child（TUST IBMs 6YO-O）.The simulations were set up as specified in C-NCAP（version 2021）three types of impact tests,in order that the influence of sitting posture angle on the injury mechanism of children’s occupants were compared and analyzed.In frontal collision,the risk of head injury increased with the increase of sitting angle,nevertheless,the probability of chest visceral organ injury decreases gradually.In side impact,there is a high risk of mild and severe head injury with the increase of sitting angle when the child occupant seated on the far side.In the whipping test,the neck load decreased by 0.9g for each increasing 15°of sitting angle,and the stress of cervical spine and spinal cord decreased with the increase of sitting angle.The 3ms resultant acceleration distinctly indicated the trend of head acceleration changed and the risk of head injury by simulated the frontal impact test based on the injury bionic model of six-year-old child standard sitting posture.The head injury criterion(HIC₁₅)has a large error for the risk assessment of head injury if the child head didn’t collide with the interior.The risk of chest injury from the 50%MPDB collision were lager than it from the 100%frontal collision,and the lung injury were more severe.But the risk of abdominal visceral organ injury reduced.The research on the injury caused by misuse of child restraint system（CRS）in the frontal collision presented the child occupant would be effectually protected when the occupant’s back closely contacted with the CRS in 100%frontal collision.In 50%MPDB collision,the rotational movement of child passengers be effectively limited only when the child restraint system is used correctly.The injury risk of child occupant caused by rotational load would be reduced.In addition,the damage probability of child ribs is very high in the frontal collision.But there is little correlation to the misusing the CRS.In conclusions,the child injuries were investigated based on the six-year-old child occupant injury bionic models with three sitting postures by simulated the frontal impact test,side impact test,whiplash test and misused child restraint system test.The injury mechanism of main body parts of six-year-old child was analyzed using the finite element method.These results will be offered the reference for comprehension of injury mechanism and development of the CRS applied to the six-year-old child occupant.This will be a foundation for assessment of collision injury and digital assessment technology for child passengers.