Study On The Injury Protection Of Child Occupant In Vehicle Offset Impact

At present,the safety research of child occupants in vehicle crash safety has been widespread,while China mainly focuses on the frontal 100% overlap impact,and has less research on the positive offset impact condition.However,the actual traffic accident shows that the offset impact also has a significant impact on the casualties of child occupants.In order to fully evaluate the safety protection performance of child restraint systems(CRS)in different impact environments,it is of great significance to study the injury risk of the child occupant in the vehicle offset impact.In this research,based on the connection between CRS and vehicle and the restraint of CRS on child occupants,finite element(FE)models of three different type of CRS were established.Using Q3 dummy FE model,the ECE R44 sled impact test simulations were conducted for this three CRSs.Results of the dummy's kinematics and accelerations in the tests and FE simulation s were correlated and verified the validity of the three type of CRS FE models.In order to study the difference of the child occupants' injuries between in the offset impact and the 100% overlap impact,using Q3 dummy and ISOFIX CRS FE model,three vehicle impact test simulations were conducted: 50 kph full frontal rigid barrier(FRB)test,64 kph 40% offset deformable barrier(ODB)test and 64 kph 25% FRB test.Comparing the kinematics and injury value of Q3 dummy,the results show that the vehicle in the offset impact rotates around the impact point and results in a large lateral acceleration;child occupants will rotated relative to the CRS and get a lager upper neck flexion moment Mx,15 Nm.In this three impacts,the injury of the child occupant in the offset impact is less than 100% overlap,and the upper neck force were more than 2000 N.Studies have shown that the 100% overlap impact is most severe in children in the frontal impact,but the child occupant in the offset impact may rotate and have a larger upper neck flexion moment Mx.It is hoped that this analysis will provide a reference for the study of the differences in children's injury in different impact conditions.In order to study the difference of safety performance of children with different types of CRSs in offset impacts,using Q3 dummy and THUMS 3-year-old children human FE model(Total Human Model for Safety),the 64km/h Euro-NCAP 40% ODB(offset deformable barrier)vehicle impact test simulations were conducted for 3 types of CRSs(5-point harness CRS,ISOFIX CRS and impact shield CRS).The results show that the three CRSs and child occupants all rotated with the vehicle,and the hands of child dummies constrained by 5-point harness CRS and impact shield CRS contacted the car door.In 5-point harness CRS,the forward excursion of child occupants are very large(the head excursion of the Q3 dummy and the child FE model were 606.41 mm and 667.14 mm,respectively);Both the CRS that were connected to the vehicle body using the ISOFIX device and the impact shield CRS,all can effectively reduce the forward excursion.The upper neck tension of Q3 dummies constrained by this three type of CRS are more than 2000 N,greater than the high performance index 1700 N.The results show that the safety performance of different types of CRS in the offset impact is obvious,and hope that this research can be a good reference for the child occupant safety research work on the vehicle offset impact safety in our country.