Finite Element Analysis And Injury Assessment Of A Three-year-old Child Occupant Based On C-NCAP (2021 Version) Protocol

With the continuous growth of motor vehicle stock,the issue of the collision safety of child occupants in road traffic accidents has attracted more and more attention.The latest "C-NCAP Management Rules(2021 version)" issued by the China Automotive Technology and Research Center Automotive Evaluation Management Center strengthens the evaluation of vehicle child occupant protection,especially the inclusion of Q3 child dummies in vehicle crash tests.In the evaluation test,there are many factors that affect the dynamic responses of the rear seat Q3 child dummy,such as vehicle collision waveform,rear seat space,child safety seat performance,etc.How to meet the Q3 child dummy safety score target has become a difficulty point in the development of child occupant protection design.In order to meet the safety target of Q3 child dummy according to C-NCAP(2021version)management rules,finite element impact model of the three-year-old child occupant can play an important role in the development of child occupant restraint systems.This study used the TUST IBMs 3YO and THUMS 3YO child occupant finite element models to benchmark the C-NCAP(2021 version)frontal 100% overlap rigid barrier crash test.In the benchmarking simulation test,output parameters of kinematic and biomechanical responses from THUMS 3YO were larger than those from TUST IBMs3 YO,which were mainly caused by the contact between the head and the chest and the excessive restraint of the seat belt.Also,because springs wre used to simulate the muscle response in the neck model of THUMS 3YO.In the kinematic response,the neck is always in a stretched state,which may affect the neck kinematic response and transfer force to the head during the collision,resulting in a large response value.The application of the finite element model of the human body with detailed anatomical structure can more realistically and comprehensively reflect the injury characteristics of child occupants in automobile collisions;therefor can further predict the damage to the vital organs of the human body.The validated biomechanical computational model of the Chinese three-year-old child occupant with detailed anatomical structure was used to assess the children injury in the frontal 100% overlap rigid barrier crash test specified in the C-NCAP(2021 version)protocol.Kinematic and biomechanical responses of the head and chest of the three-year-old child using different restraint systems were discussed and analyzed.Simulation results showed that utilizing the seat belts can greatly reduce the injury risks of child occupants in the frontal impact.And a five-point seat belt has better protection performance for child occupants than a three-point seat belt.By extracting the kinematic and biomechanical responses of TUST IBMs 3YO in four occupant protection dynamic tests of C-NCAP(2021 version)management rules,the injury mechanism of child occupants under different loading conditions were explored.The results show that in the four occupant dynamic protection tests of C-NCAP(2021 version),the rear child occupants may suffer more serious injuries in the side pillar impact test.In a car side collision accident,due to the intrusion of the door and the lateral displacement of the occupant,the head collides with the vehicle interior and the child restraint system,resulting in a higher risk of injury in a side collision than in a frontal collision.Therefore,future occupant protection regulations should incorporate the protection evaluation of child occupants in side collisions as well.In this study,a biomechanical computational model of a three-year-old child occupant with sound biofidelity can be conducted to assess the injury assessment parameters required in the C-NCAP protocol.Furthermore,children injury mechanisms can be researched in depth by analyzing the biomechanical responses.This study can help to evaluate the children protection devices and testing car model in a comprehensive and multi level.The results could have an important application value for the design and optimization of the Child Restraint System.This could provide a basic data for the development of digital injury assessment in future safety design.