| With the continuous growth of vehicle ownership,road traffic accidents occur frequently,the number of casualties is high,and there are countless property losses.The vehicle passive safety is increasingly a cause for concern since it is particularly important when the traffic accident is unavoidable.The safety of rear seat occupants has not got enough attention in the process of research of automotive passive safety technology.Note that frontal crash is the major crash type,and rear seat of the car has a higher frequency of use.Therefore,it is of great value to build a more perfect rear occupant restraint system in the vehicle front crashes.This paper takes the rear occupants as the research objectives,through combining rear car collision test with computer simulation.On the basis of the finite element model of the rear occupant restraint system,an airbag and a rotatable cushion are added into the finite element model to protect rear occupant.A more perfect rear occupant restraint system was constructed,and the matching scheme of the best protection effect was found by parameter matching.The study was carried out by following aspects:The functions and advantages of the non-linear finite element software LS-DYNA are analyzed;the theory of non-linear finite element and the commonly used finite element method in vehicle crash are introduced;and the development of airbag and future development direction are summarized and analyzed.According to China New Car Assessment Program(C-NCAP),the crash test of full frontal rigid barrier was conducted in order to collect acceleration signals from the vehicle and injury criteria of the key parts of rear 5th percentile Hybrid ? female.Furthermore,the frontal 40% overlap deformable barrier collision test,the left 30 degree angle collision and the high speed collision test are carried out,and the collision acceleration signals of the x and y axes in the collision process are collected.A finite element model of rear occupant restraint system was constructed by using LS-DYNA.Under the same acceleration from vehicle full frontal crash,the injury criteria of rear female dummy is obtained by simulation calculation.Then the injury criteria between simulation calculation and the crash test were compared.Results showed that there was a good consistence between test results and simulation calculation with regard to dummy's injury criterion from head,neck and chest.This proved that the simulation model could be used to simulate the process of vehicle frontal crash.It is proposed to install the rear airbag by improving the internal structure of the front seat back of the vehicle.In adjusting the front seat backrest angle at the same time,to do airbag angle adjustment,the expansion direction of the airbag is always facing the rear occupant.After simulating the effect of the airbag on the dummy in frontal crash,the result shows that airbag has better protection effect on the dummy while the neck of the dummy in the late collision damage has a tendency to rise.A more perfect rear occupant restraint system was proposed to protect rear occupants.Taking the dummy's chest deflection as the optimization objective,the parameter matching involves the ignition time of the airbag,the limit of the seat belt and rotation initial time.The result shows that the safety limit of the seat belt is 2.7kN,the ignition time of the gasbag is 23 ms,and the cushion turn time is 16 ms,which achieves the best protection effect on the dummy.Then,the protective effect of the matching scheme on the dummy is verified by means of high speed collision and different collision type,which shows that the matching scheme is better in high speed collision than that in the low speed collision,and it also has some protection effect on the various types of crashes. |
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