Optimization Of Crashworthiness For A Passenger Car Based On Lightweight Design Of B-pillar

In present-day society, lightweight has become a hot research topic inautomotive industry due to the severe problem of fuel crisis and environmentpollution. The statistics show that petrol consumption may decrease6-8%if thelightweight effect of full vehicle reaches10%. As the automotive structure possessesabout40%weight of full vehicle, the weight reduction in body structure is one keyway to achieve fuel efficiency, harmful emissions reduction and raw materials saving.At the same time, there have been growing concerns over vehicle safety cases byincreasing legal and market demands. Thus, lightweight and crashworthiness are twocrucial aspects of automobile design. The lightweight design should not compromisethe safety of the car occupant.A lot of literature research on lightweight design and crashworthiness has beendone firstly in the paper. We also described several lightweight design technologiesincluding Tailor Rolled Blanks. Then the research status of vehicle crashworthinessand the relevant collision regulations were introduced. The finite element methodused in collision simulation was presented. Some experimental design method,mathematic surrogate model and optimization algorithm were summarized briefly.The full side impact car model, including side impact barrier was establishedaccording to the China New Car Assessment Program (CNCAP). A real car sideimpact experiment has been already done, by comparing the time history ofacceleration of the car body and deformation modes of key parts, the simulationgives a reasonable fit into the experiment results. Then we evaluated and analyzedthe simulation result of side impact. Base on the simulation result, some componentsincluding the door, the threshold, the B-pillar and the floor were selected to make asensitivity analysis. The result of sensitivity analysis shows that the B-pillar is themost key factor influencing the occupant safety in side impact. The computersimulation of roof crush is based on the test of FMVSS216. Another sensitivityanalysis on roof crush was also been done. Compared with the A-pillar, C-pillar andthe roof-rail, B-pillar is also one of the most important components that mainlyaffect the roof strength.An integrated approach is applied using uniform design, finite element method,Kriging approximation and genetic algorithm. Optimization of the B-pillar isproposed by using tailor rolled blanks (TRB) concept under the constraint of vehicleside impact and roof crush. The weight, intrusion, intrusion velocity at the middlepoint of B-pillar and the resistant force of roof crush were chosen as the optimization objects, and the thickness of5segments of the B-pillar were chosen asthe design variables. After optimization, two types of TRB structure (TRBⅠ andTRBⅡ) are proposed in the paper. It is shown that the weight of the B-pillar can bereduced by36.43%and31.57%，respectively, without the loss of safety by TRBstructure. Compared with two TRB structure, TRBⅠ is the best in weight reduction,while TRBⅡ is more reliable and more suitable for engineering due to smoothtransition.The result of this study shows that: Through the sensitivity analysis, we foundthat B-pillar is the most important component that affects side collisioncrashworthiness and roof strength. It demonstrates that the optimization method bycombination of uniform design, finite element method, Kriging approximation andgenetic algorithm is available in lightweight design of B-pillar. Moreover, TRB canbe potentially used to design B-pillar to reduce weight, without loss safety.