| Traffic accident situation is various, among which, frontal collision is the most frequent,which topped the death toll list. The purpose of automotive design for crash safety is occupant protection, when frontal crash happen, the vehicle is involved crumple, impact pulse can not only characterize the collision response and reflect the crashworthiness but also has close relation with occupant injury, reasonable impact pulse can effectively reduce occupant injury. So the optimization for impact pulse is not only of great significance, and also the hot spot of crash safety. This thesis took SUV as research object, studied the relationship between the frontal impact impact pulse and the occupant injury, developed the target impact pulse, and carried out the optimization design of impact pulse based on energy management and material thickness matching, which effectively reduced the occupant injury.The main research work and achievements are as follows,(1) The vehicle FE model has been developed and its reliability has been verified through energy analysis.According to the characteristics of vehicle general arrangement,EDTW has been selected as simplified form of impact pulse. It is found that EDTW is effective when substituting both the detailed and simplified pulse into occupant restraint system. The results of occupant injury sensitivity analyzed through DOE shows that the parameters h1 and h2 have greater impact on occupant injury. Formulated from the results of sensitivity analysis and the difficulty of matching the restraint system, the target pulse points out the direction for structural optimization.(2) The pulse objective was converted into energy target and, according to the deformation characteristics, bumper and first segment were selected as structure to be optimized. Improvement schemes for first segment have been proposed, and optimal scheme has been selected by results analysis and comparision. Shape variables with high sensitivity were selected for induced groove optimization based on RSM and GA genetic algorithm, and the energy absorption is closer to the target after optimization. Improvement schemes are proposed for bumper structure, and eventually optimal scheme has been elected.(3) The thickness matching scheme for impact pulse optimization was proposed.Improvement schemes for excessive intrusion problem were proposed, and through the comparative analysis, the optimal scheme has been elected. The Half vehicle model was built and its reliability was verified. 13 sheet metal thickness properties with high sensitivity were chosed for optimization by means of DOE. The RSM of NISE, mass and intrusion response with hige accuracy were built on the sample data. Multi objective optimization was performed on RSM with minimization of mass and NISE as objective, intrusion as constraint condition and MOPS as optimization algorithm, and the pareto and recommended solution were obtained. 10 pareto were selected to be compared with the recommended solution, and finally the recommended solution was chosed as the best thichness group. After optimization,the impact pulse is more close to the target, the NISE and vehicle mass decreased by 0.5%and 68.1% respectively, the intrusion of some parts has increased, but it is within the scope of the constraint. Occupant injury index HIC36, chest T3 ms, chest compression and WIC has fallen by by 11.54%, 10.87%, 3.92% and 10.74% respectively. The thickness matching not only improved the pulse, reduced the occupant injury, but also realizes the lightweight which is the requirement of the times. |
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