Research And Optimization Of Abdomen And Chest Injury Of Child In Impact-shield Restraint System

With the development of automobile industry in China,the safety of passenger has been paid more and more attention by related industries.Among them,children occupants are often more likely to be injured than adults due to their unique physiological characteristics in traffic accidents.In the latest ECE R129 regulation issued in Europe,it not only improves the usingstandard of child restraint system,but also adds new injury index such as abdominal pressure and chest compression.This article takes a impact-shield child safety seat as the research object,and conducts research on the abdomen and chest injuries of the child occupants to improve the collision safety.Based on the ECE R129 regulations,the frontal collision simulation model with the Q series three-year-old dummy was established,and the validity of the model was verified by trolley test.The frontal collision simulation analysis of this safety seat was carried out on four factors: the installation height of the impact-shield(relative to the H position of the dummy),the height of the impact-shield,shell stiffness of the impact-shield and material stiffness of the foam.Using orthogonal test to find the factors with a significant impact on the abdomen and chest injury of children.Conduct full-factor test on factors that have significant impact,the approximate model of injury index is constructed based on the result of the full-factor test,and the optimal parameter group of injury index is found through multi-objective optimization based on genetic algorithm.The research shows that: the installation height position of the impact-shield when the safety seat achieves the best protection is 0-20 mm,the height is 157-190 mm,the thickness of the reinforced rib is 2.5-3.5mm and the foam stiffness coefficient is 1.0-1.5.The factors that have a significant impact on the damage of children's dummy are the installation height position of the impact-shield and the height of the impact-shield.When the current height position of the impact-shield is 0mm,the bottom can be well restrained at the lowest position of the dummy's pelvic.When the installation height of the impact-shield is 190 mm,the top can be well restrained at the uppermost position of the dummy's chest.Therefore,the maximum abdominal pressure ofthe dummy decreased by 16.3% and the maximum chest compression decreased by 9.1%.The effect of the seat structure on the abdomen and chest injury of the dummy is studied.The inclination of the seat cushion and the stiffness are taken as the research objects,and the method of full factor test is used.The results shows that the protection for the child occupants gets better when the inclination and stiffness of the cushion increase.When the inclination angle is 30 degree and the shell thickness is 4 mm,the deformation of the cushion is smallest,and the“dive” trend of the dummy is faintest.Therefore,the maximum abdominal pressure of the dummy is reduced by 6.5%,and the chest-3ms-acceleration is reduced by 6.1%.In order to solve the problem of different abdominal injury on the left and right sides of the child when the three-point safety belt is used to bind the impact-shield,three simulation models of different installation methods of the impact-shield are established.The results shows that when the impact-shield is directly fixed on the seat shell structure,the abdominal injury of the left and right sides of the child dummy gets consistent.At the same time,it can effectively avoid the "dive" phenomenon of the child occupant during the collision.The maximum pressure was reduced by 14.1% and the maximum chest compression was reduced by 11.1%.Finally,a comprehensive optimization simulation model of the impact-shield safety seat was established.After the optimization,the maximum abdominal pressure of the dummy was 1.12 Bar,and the optimization degree reached 39.13%;the chest compression of the dummy was 27.84 mm,and the optimization degree reached 26.39%.The study on the optimization of the impact-shield safety seat on the abdomen and chest injury of children has concluded that the most critical way to reduce the abdomen and chest injury of children in frontal collisions is: 1)The impact-shield needs to be restrained on the pelvic part to avoid the phenomenon of "dive" of child occupants during the collision;2)By spreading the restraint part to the chest of the body,the collision impact load can be effectively dispersed to reduce the abdominal and chest injuries of the child occupants.