Optimization Design Of Frontal Bumper System For Requirements Of Both Pedestrian Lower Leg Protection And Low Speed Impact

As one of the key components of car, the frontal bumper system plays an important role in the requirements of pedestrian lower leg impact and low speed impact. Frontal bumper system has a direct influence on pedestrian low leg injuries as the most front-end body part. In addition, frontal bumper system protects the principal parts of the car such as fender, radiator, hood and longitudinal beam at low speed impact. Therefore, the frontal bumper system needs to be analyzed and designed to meet the requirement for both pedestrian protection and low speed impact.The purpose of this thesis is to optimize the design of the vehicle front bumper system, improve the characteristics of collision energy absorption to meet the requirements of the regulations on pedestrian lower extremity protection and vehicle front performance at low speed collision.Firstly, the FE HBM-LEG model constructed by the center of vehicle and traffic safety is used to compare the biofidelity of TRL-LFI and LSTC-LFI legform impactor. Analysis results show that neither TRL-LFI nor LSTC-LFI can predict the knee injury well, especially the knee shear displacement. But just compared the TRL-LFI and LSTC-LFI, LSTC-LFI is superior to TRL-LFI. In the follow-up study, we adopt the LSTC-LFI to evaluate the original car’s pedestrian lower leg protection performance. The results show that the original car’s performance is not idea and cannot satisfy the value of pedestrian lower leg required by the EEVC.At the same time, we evaluate the low speed impact performance of the original car according to Chinese GB17354-1998and Canada CFVSS215respectively. For the impact speed regulated by the CFVSS215is larger than the GB17354-1998, the pendulum’s energy of CFVSS215is also larger than the GB17354-1998. The CFVSS215has more strict requirements on the frontal bumper system. The results show that the original car model can meet the requirements of the GB17354-1998, but cannot satisfy the requirements of the CFVSS215.The study adopts the surrogate model theory and the relevant optimization method, using the crash simulation software LS-DYNA to bring out the optimization method and process for both pedestrian protection and low speed impact requirement. Through compared analysis, the metal energy absorber (EA) structure on GEELY EC7was adopted in this paper. Then the sensitivity analysis between the6design variables of the front bumper system and targets was assessed with the help of orthogonal experimental design and comprehensive equilibrium methods. Four design variables of the energy-absorbing plate thickness, energy absorbing plate X dimension, energy absorbing plate size in Z direction, the height of the bumper beam center were selected for the frontal bumper system optimization. The Response Surface model was established by using Latin-hypercube design methodology to provide the Response Surface approximation with experimental samples. At last, the NSGA-Ⅱ algorithm was used to optimize the frontal bumper system for lower leg impact and low speed impact. The pedestrian lower leg protection and low speed impact performance was improved significantly at the same time the requirements were meted respectively...