An Optimization Study On Crashworthiness Of Front Bumper Assembly In Vehicle Frontal Impact

With the increase of the car ownership, the number of road traffic accidents anddeaths has always been at a relatively high level. The data shows that in all kinds ofcollision accident forms, the occurrence probability of frontal impact is the highest andgenerally more serious damage to the occupant. The probability of occurrence of theaccidents is the highest when the overlapping rate is40%and100%, and therefore,improvement of crashworthiness of full-front impact and offset impact is of greatsignificance.First, based on extensive literature study, this paper analyzed the developmentand status of automotive regulations both in the domestic and foreign. Developmentprocess of China’s laws and regulations were given an elaboration, and regulations offrontal impact and New Car Assessment Program (NCAP) of several typical countrieswere compared. Then combined with LS-DYNA, some finite element theory andmethods involved in the automotive crash simulation are briefly introduced.Then a brief description considering with parameters of the bumper system wasgiven. The strain rate’s influence on material performance was gained by comparinglongidunal beam material parameters and the non strain rate model. The reasonableparameters’ values were achieved by comparing the crashworthiness of bumper beamswith different heights and solder distances. On the basis of the work above, the vehiclefinite element model was established. The full and offset frontal impact models werealso established according to the2012C-NCAP regulations. The model validation wascompleted by comparing the acceleration curves of tests and the model results.Since the deformation of the front rail in the test is not ideal, the thickness ofthe rail was optimized to get the ideal collision performance. This paper emphasizedon optimization, in which process the sample points were selected by taking theuniform design method and an agency model was established through krigingmethod, the optimum point was found through the multi-objective genetic algorithm.The thickness of the longidunal beam was optimized three times for100%rigid wallcollision model,40%of the deformable barrier collision model and100%rigid wallcollision combined with model with40%deformable barrier collision model. Theresult showed that the acceleration of the B-pillar in full-front impact reduced4.7%and energy absorption per per unit of quality of longidunal beam in offset impactdecreased14%.The research shows that: the influence of strain rate on material is evident; during the collision process the strain rate should be considered to select parameters.The solder distances and the front bumper beam height should be in the reasonablerange to ensure a proper force passing path in the back-end components. Thelongidunal beam optimization proves that: taking into both kinds of the impactsituation account improved the crashworthiness in both offset and full front impacts,the comprehensive improvement of the vehicle front crashworthiness was achieved.