Research On Forward Design Method Of Vehicle Frontal Impact Safety Based On Force Transmission Path Stiffness

Evaluation and optimization of vehicle impact safety performance is an importan t subject of modern car industry research. Reversing technology is widely used in vehicle body design in the domestic, usually the design of new vehicle refers to benchmark ones when analysis and optimization of passive safety performances is processing, which often rely on engineering experience and lack of effective theoretical guidance. Forward design is a conception that finish the body structure prediction and guide the detail design according to the performance target s of structure and design requirements. The problem of solving structure design variables through the design targets belongs to the category of forward design, which often solved by optimal algorithm that needs many times iterative calculation, it reveals the character of model must be efficiency and precision. However, using finite element model to solve highly nonlinear large deformation problem usually takes a few hours for single calculation, and more calculation time will be needed when processing thousands of iterative calculation. Thus it is significant and valuable to find out efficiency design method of vehicle crashworthiness.In concept design phase, research on distribution of collision force transmission path stiffness according to targets of crashworthiness belongs to forward design conception. In order to find simulation method which is efficiency and precision, a modeling procedure as well as modifying and optimization method of full-width front impact performance is presented based on multi-rigid-body model(MBM). Finite element model(FEM) of a benchmarking which have been identified by test is used in obtaining joint stiffness, coordinate, rigid body mass and inertia to build raw MBM. By defining reliability function, using computer reversing technique, the MBM stiffness is modified and match perfectly with FEM. MBM developed by this procedure is precise and efficient, thus it can be used on body stiffness distribution and force transmission path forward design at early stage of vehicle design.The optimization platform is built based on revised MBM and multi-objective genetic optimization algorithm as long as o ptimization design targets are decided according to the characteristics of collision acceleration curve, and consider deformation as one of constraint conditions. After the optimal stiffness scale factor combination is found, the key force transmission path stiffness distribution pattern is solved.In order to verify reliability and precision of the optimal soluti on, the correlation between metal thin-walled straight beam energy absorption or collision average force on cross section and parameter of cross section size, material properties or thickness is discussed. So the relation of optimal stiff scale factors and these component properties is found, with which the material, thickness and cross section size of several key component can be designed based on FEM and the optimal solution is verified eventually. Result indicates that optimization on force transmission path stiffness distribution based on MBM seems both high efficiency and precision.This optimization method that based on multi-rigid-body simplified model and engineering optimization platform is used to obtain good vehicle crashworthiness, with which the conception of body stiffness forward design and structure optimization is exactly realized. The method can improve calculation efficiency as well as avoid repeatability and blindness in later design. Thus, it has important guiding significance on the whole body design process and also can be helpful with the auto industry forming effective passive safety optimization strategy and engineering design process.