| Along with the growth of auto possession, road traffic accidents have already become a worldwide social problem. Road traffic accidents will not only cause huge economic losses, but also can bring serious disaster to human health safety. Statistics show that in the road traffic accidents causing person damage, the probability of frontal crash is about 40%, which is far higher than other types of collision form. And in the frontal crash, the serious injury rate is the highest when the overlap rate is 30%-40%, and mortality is the second rank only after the entire width collision. Therefore, how to improve the offset impact crashworthiness of vehicle has become an important subject.The history and current situation of car collision safety both on board and domestic were expounded firstly. Then the relevant crash safety regulations were introduced and compared. The finite element method used in auto crash safety simulation was introduced on the application level. Some typical experimental design method, approximate agent model and optimization method were briefly summarized respectively.An offset impact finite element model of a domestic vehicle was established in accordance with the requirements of Euro-NCAP regulations, and the reliability and effectiveness of the model is verified. The offset impact safety of the car was analized and evaluated according to the intrusion requirement of NCAP scoring. The improvement scheme of the topology structure, plate thickness and materials etc. was put forward according to analysis result. The improved effect was demonstrated using simulation results. Eventually the vehicle peak acceleration decreased by 6.6%, and the intrusions of steering column and foot pedals were dramatically reduced, so was the backward quantity of'A'column, the NCAP penalty is reduced from 2.86 points to 1 points, therefore the risk of injury is decreased greatly.A new vehicle body structure crashworthiness optimization method was advanced with uniform design, finite element method, artificial neural network and genetic algorithm, which was applied to the crashworthiness optimization design of the longitudinal beam of the car. The finite element model was built in Hypermesh, and validated by a sled crash test. According to the requirement of crashworthiness of longitudinal beam, the energy absorption, weight and maximum impact force were chosen as the optimization objects. A most appropriate thickness compounding of plate thickness of 4 parts of the longitudinal beam were obtained, they are t1=1.6mm, t2=2.2mm, t3=2.0mm, t4=2.6mm. The energy absorption is increased by 12% with limited increase of maximum impact force and weight. Then the optimization effect was demonstrated by a whole vehicle offset impact simulation with replaced longitudinal beam. The results show that the peak acceleration is decreased by 10.8%, and the energy absorption of the main components in frontal carbon is increased a lot. The offset impact safety of the passenger car is improved further.The results of the study show that: Crashworthiness of vehicle in offset impact could be enhanced greatly by targeted improvement from topology structure, plate thickness and the material aspects of relevant vehicle body components; the crashworthiness optimization method combined with uniform design, finite element method, artificial neural network and genetic algorithm is very suitable for multi-parameter optimization of automotive structural parts; the component crashworthiness optimization based on sled test is a good guidance of vehicle safety improvement, that can be used as an important reference for the vehicle optimization. |
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