Structural Design And Simulation Research Of A Four-point Child Safety Belt For School Buses

In recent years, the school bus safety problem has become more and moreprominent, and pupils occupant safety protection has become one of the importantissues in the study field of school bus safety. Most domestic school buses areequipped with two-point seat belt, and some school buses also have three-point seatbelt. However, both the two seat belts have some disadvantages to some degree:two-point seat belt has no restraint on the upper body,so it easily makes children’ headinjured owing to children’s run into the front row seats when the school bus has acollision; because the growth of children’s bone is not complete, and the heightdifference is rather big, it is easy to hold the necks of children when wearing athree-point seatbelt.Based on the disadvantages of existing school bus seat belts, a four-point childbelt matching with the school bus seat is proposed in the thesis. The belt is suitablefor children aged from3to10years, and it can be handled easily and be worecomfortably. What’s more,the length of the belts can be adjusted to suit differentshape of children. The four-point seat belt is equipped with automatic EmergencyLocking Retractor, which can effectively prevent children from moving the body. Asa result, it can avoid children taking part in “diving” phenomenon when the schoolbuses brake urgently. A structural design and working principle of the school bus’sfour-point children belt is conducted in this thesis, and the samples of four-pointchildren belt and elementary school bus seats were manufactured at the factoryoutside of school.A frontal impact of sled contrast test was made for two-point seat belt and four-point belt, test conditions referring to the requirements of GB24406-2012<Thestrength of student seat system and their anchorages of special school bus>.The MADYMO was used to develop the frontal crash simulation model whichincluded two-point seat belt and four-point children belt based on6-years-old childrendummy. Then,the effectiveness of the two groups of model was verified according tothe test data. The stipulation of elementary school bus seat spacing in GB24406-24406is not less than690mm. But the requirement of elementary school busseat spacing in GB24407-24407is at least550mm. Through actual inspection on themarket for the elementary school bus seat spacing, it was found that the size of theseat spacing was mostly concentrated in the range from540mm to610mm. Based onthe validated model, changing the distance between front and rear seats, taking theseat spacing value of620mm and530mm, operating models respectively, probing the protection mechanism when children dummy wear two-point seat belt orfour-point children belt. Also based on550mm actual working condition of the schoolbus seat spacing,the four-point child belt of school bus simulation model for3-year-old,6-year-old,10-year-old was established, and the protection effect offour-point child belt for children aged approximately from3to10years old in frontalcrash was under discussion.The result was that under the premise of meeting theinjury criterion set by the international standard,four-point children belts whichrestrained children’s body motion on the school bus could effectively reduce thesecondary injury.