| With the increasing of the number of the vehicle possession, traffic accidents also increased. So, vehicle safety takes more attention than before. Side impact accidents account for 39.5 percent of all traffic accidents in 2005 in China. As the grade crossing is the major pattern of urban traffic road in China, the occurrence probability of side impact accident is the highest, and the injury rate and death rate are both the highest. In side impact, because of the side structure's weaker deformation endurance and the vehicle has weaker energy absorbing ability, the passenger will suffer much more injury risk. Then side impact research has become an important topic in the passive safety area. The vehicle side impact performance has to be improved. The regulation on the occupants'protection in side impact accidents which was developed by China Automotive Technology & Research Center according to ECE R95 has been brought into effect in July 1st 2006, and New Car Assessment Program(C-NCAP)was also issued at the same time.The aim of the thesis is to research the passengers'injury biomechanics in details and present some countermeasures to protect the passengers and discuss their validity to provide some use for reference for improving vehicle side impact safety. Firstly, the paper compared and analyzed the different side impact regulations, based on a great of literature concerned reading, it researched and summarized the knowledge of passengers'head, thorax, abdomen and pelvis injury biomechanics in side impact in details, then built the mobile deformable barrier model and the full vehicle side impact finite element model by utilizing a certain foreign full vehicle finite element model. By using computational simulation method, the full vehicle FE model and MDB models were validated by comparing it with the requirements of rules and test data. According to GB 20071-2006 rules, side impact simulation was done. The car crash deformation was calculated by using LS-DYNA, and the dummy injury parameters were obtained by using MADYMO software. Some injury parameters has gone beyond the limit of the rules. In order to improve its crashworthiness, some effective countermeasures including using side impact beam in frontal door and its different configurations and using thorax side airbag were proposed.The effects on passengers'injuries of the countermeasures were also analyzed particularly. For the reinforcement bars, the RDC has reduced by 11.92%~25.45%, the reduction of the PSPF was 11.51%~40.19%, and the reduction of APF was as much as 53.47%~65.30%. All parameters got the required value except for the RDC and VC of upper rib. To get better improvement, based on the reinforcement bar which gets the best performance, the paper proposed the thorax airbag, analyzed the influence of major parameters on its protection performance and got the optimized project of thorax airbag. The upper RDC and VC has reduced 5.82% and 17.12% with thorax airbag, and the two parameters got the reduction of as much as 29.80% and 37.21% with the combination of reinforcement bars and thorax airbag and both reached the required values. The simulation results theoretically showed their positive effects and that they were strictly helpful on improving the vehicle side impact performance.
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