Research And Optimization Of Side Impact Protection Factors For Child Safety Seats Based On ECE R129

Since the main form of transportation in cities is intersection,the traffic conditions in China are complex and it greatly increases the probability of side collision accident.Because of the high fatality rate of side impact accidents,child occupant side impact protection has drawn more and more attentions.In order to reduce the risk of injury to child occupants in side impact,the ECE R129 standard has been issued,which adds side protection requirements.To improve the side impact protection capability,the design parameters and side impact protect structure of the child safety seat were carried out based on the research and the optimization analysis.The side impact trolley simulation model of Q series 1.5-year-old dummy was established by the combination of finite element and multi-rigid body.After verifying the validity of the model,four child safety seat design parameters:the thickness of the headrest,the stiffness of the headrest cushion foam,the gap between the headrest and the dummy’s head and the thickness of the seat wing were selected as the research objects.Then,the study on the influence of side impact protection for the child safety seat was carried out by simulation.To ensure the accuracy and efficiency of the optimization,experimental design and variance analysis were used to select the optimal parameters.After constructing the response surface approximation model of the injury assessment criteria,the multi-objective optimization method based on genetic algorithm was used to solve the optimization problem.In order to improve the side impact protection ability of the child safety seat,the SIP device was installed.After the side impact dynamic test,the results showed the side protection performance of SIP was poor.Therefore,side impact model with SIP was built for study and optimization.After verifying the validity of the model,in terms of the structural rigidity,length and installation position of SIP,their effects on side impact protection of child safety seats were studied.The optimal design of SIP was determined by experimental design and comprehensive comparison.The results show that the optimal headrest thickness range is 3.5 to 4.0 mm,the best headrest cushion foam stiffness range is 1.25 to 1.5,the optimal range of headrest and dummy’s head clearance is 25 to 35 mm,the best seat wing thickness is 1.8 mm.After optimization,it is found that when the headrest and dummy head gap is 45 mm and the seat wing thickness is 1.8mm,the child safety seat has the best side impact protection.In this case,the 3 ms head synthesis acceleration a_H is 63.2 g,which is 18.8%lower than the initial value,and the head performance criterion HPC₁₅ is 374.2,which is 22.2%lower than the initial value.On the other hand,dummy’s head injury can be reduced by decreasing the stiffness of the SIP,increasing the length of the SIP or installing it on the side of the child dummy’s pelvis.The optimal design for SIP was came out which is:polypropylene,143 mm length with mounting position on the side of dummy’s pelvis.In this case,the 3 ms head synthesis acceleration a_H is54.2 g and the decrease is 30.5%,the head performance criterion HPC₁₅ is 230.1 and the decrease is 45.8%.Through a comprehensive analysis of the child safety seat design parameters and SIP parameters,the following conclusions are drawn:delaying the moment when children’s head contact the seat wing will reduce the Y-direction speed of head,it can effectively reduce the children’s head injury from the side impact.