汽车碰撞安全基础 (15).pdf
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1、 1 Simulation Analysis of Frontal Impact of 8-Year-Old Child Passenger in Booster Seat and Adult Seatbelt Yi Huang,Yuanbo Wang and Qing Zhou1 2 1.State Key Laboratory of Automotive Safety and Energy,Beijing,100084,China 2.Department of Automotive Engineering,Tsinghua University,Beijing,100084,China
2、y- Abstract:Impact safety issues of child passengers of 7-12 years old are not addressed as well as those of child passengers of 6 years old or younger.Using the newly developed finite element model of 8-year-old child dummy,protection effects of frontal impact provided by the existing restraint sys
3、tem,including booster cushion and adult seatbelt,are assessed.An optimization platform based on the simulation model is built for studying the influences of a number of parameters of the restraint system.The parameters include D-rings position of the seatbelt,pretensioners firing time,and height of
4、booster cushion.Injury responses in terms of the chest compression and the abdomen penetration are examined.The results of this study may be helpful for design of child restraint system for older child passengers.Keywords:Child Dummy Model,Child Restraint System,Optimization 1.Introduction Child pas
5、sengers impact safety in vehicle crashing accidents has been a great public concern in recent years.Regulations have been carried out to evaluate the performance of child restraint system.However,the regulations concentrates on some special sizes of child passenger dummies.In the regulation tests,th
6、ere is no dummy model which can represent child passengers aged between 7 and 12 years old.In reality,the child passengers that fall in this range who are too big to be fitted in the car seat,are usually restrained with adult seatbelt and booster cushion.These equipments are reported to be able to m
7、itigate the seatbelt syndrome suffered by the child passengers in the crash accidents1.However Trosseille et al.and Jermakian et al.reported that,inappropriate usage of such system may impose side-effect to the safety of the child passengers2 3.Consequently,the interplay between the passenger,the se
8、atbelt configuration and the booster cushion should be investigated.In this study,an 8-year-old dummy model developed in the previous work was used.A simulation environment was built on the basis of the ECE R44.To make the adjustment and the fitting of the seatbelt automatic,several preprocessing te
9、chniques were used in conjunction with an optimization tool.Thus an optimization platform was built to study the influences caused by the adult seatbelt and booster cushion over the 8-year-old dummy models response.2.Model Description In order to evaluate the protection performance of the adult seat
10、belt system to the 8YO child dummy model,a suitable test environment should be chosen.In regulations,the child occupant restraint systems are evaluated in test benches.The configuration of the test bench can be regarded as a typical vehicle interior environment,which mainly consist of the adult seat
11、belt,the seat and some corresponding anchorage parts.In this study,the test bench configuration was built on the base of the ECE-R44 regulation.Figure 1 shows the real ECE-R44 test bench and the FE model.The most important components of the test bench are the cushions,which support the dummy model d
12、uring the frontal collision simulation.The other parts of the bench were generally ignored.The two cushions were modeled with solid elements.The outer surfaces of the cushions were covered with a layer of null shell elements to improve the contact behavior.2(a)ECE R44 Test Bench(b)Finite Element Mod
13、el Figure 1 Test Bench Figure 2 shows the 3-point seatbelt configuration of the test bench.The position of the anchorage points of the seatbelt was defined according to the ECE-R44 regulation.The seatbelts path was determined by 5 points,which were the locations of the upper and lower slipring,the r
14、etractor and the two anchor points positioned deep in the seat cushion.By varying the locations of these five points,different seatbelt paths can be obtained.The seatbelt path may influence the interaction between the seatbelt and the dummy model,which will be investigated in this study.Figure 2 Sea
15、tbelt Configuration in ECE-R44 As this is a preliminarily methodological study,a simple block made up of shell elements was used to represent the booster cushion.The height of the booster cushion was originally set to 80 mm and could be scaled.The shell elements thickness could be adjusted to obtain
16、ed different booster cushion stiffness.Furthermore,a pretensioner and a load limiter were integrated into the seatbelt model.The characteristics of these two components came from the literature4.The pretensioner was able to pull in 120 mm of seatbelt in 20 ms.The load limiting level was set at 5 kN.
17、The firing delay was adjustable.Figure 3 shows the 8YO dummy model placed on the sled with the booster cushion and the adult seatbelt.A crash pulse in compliance with the FMVSS 208 regulation was used in this model.The velocity of the bench is decelerated to-48 kph in 120 ms.The maximum deceleration
18、 of the bench is 17.3 g.The pulse used here is less severe than the pulses used in ECE-R44 regulation.However,it can represent the process of a frontal collision of a vehicle.T C RAB0 C A B0 R TA B0:Anchorages C:Upper Slipring T:Lower Slipring R:Retractor YZX Z Shoulder Belt Angle Lap Belt Angle 3Th
19、e responses of the dummy model,including HIC value,head excursion,upper thorax deflection,lower thorax deflection and abdomen penetration were injury outputs for assessing the performance of the restraint system.Figure 3 8YO Dummy Model Placed on the Test Bench 3.Model Manipulation Before the simula
20、tion of occupant restraint system,the seatbelt should normally be fitted to the occupant dummy model in the preprocessing phase before the simulation starts.This is mainly done manually with the help of some preprocessing software tools.When the dummy models position is changed or the seatbelts path
21、 is modified,manual attendance is needed.Nowadays,as optimization techniques have been extensively used in the investigation or design of the occupant restraint system,more influencing factors of the restraint system or the occupant are taken into consideration.The simulation matrix is becoming larg
22、er.An automatic method to manipulate the positioning of the dummy model and the refitting of the seatbelt would save large amount of preprocessing work.Above all,the preprocessing can be controlled completely by the optimization tool.In this study,such an optimization platform was built.Figure 4 Wor
23、k Flow of the Optimization Platform Figure 4 shows the work flow of the platform.The optimization tool LS-OPT acts as a command center.It determines the test matrix.A batch command reads the parameters in each test,and then scales the booster cushion to the desired height,translates the dummy model
24、according to the adjusted cushions height and invokes the Oasys PRIMER 9.3s seatbelt refitting module5 6.The batch checks the refitting quality and transfers the preprocessed simulation model to the LS-DYNA.LS-OPT analyses the output of LS-DYNA and prepares LS-OPT -Design of Experiment-Construct res
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