Crashworthiness Optimization And Application Of Step By Step Energy Absorbing Beam

Nowadays, automotive industry is highly developed, and safety has become an important factor that influences people's decision to buy a car. Front rail is the main energy absorption device during frontal impact, and its energy absorbing ability affects the vehicle's front safety deeply. During frontal impact, front rails are too short to absorb sufficient energy in a limited deformation scope, that will lead engine and other accessories to intrude into passenger cab, thus injury risk of passengers will be increased. However, oversized stiffness of front fail will result in bending buckling, which will cause the vehicle to absorb dynamic energy inefficiently, consequently, higher acceleration and severe deformation of passenger cab will be generated. These results are very disadvantaged for passenger protection.A step by step energy absorption method based on reverse design theory was presented in this paper, namely, reinforcing plates were added at different positions of the front rail. In this way, the plates could be deformed step by step, and the ideal requirement of crash acceleration curve would be achieved. According to this method, a quadrangular and an octagonal step by step energy absorbing structures were designed, the finite element models of these structures were also developed and validated by sled test.Based on experiment design method and response surface method, crashworthiness of the quadrangular and octagonal step by step energy absorbing structures were optimized. Firstly, the main structure factors that influenced crashworthiness effectively were filtered, thus crashworthiness formulations of the structure were constructed using Latin Square experiment design method and response surface method. Afterwards, numerical optimization method was used in optimization of crashworthiness formulations, so an optimal design was obtained. Secondly, crashworthiness formulations of the octagonal step by step energy absorbing structure were also constructed by uniform experiment design method, then multi-objective optimization of the formulations were performed, and a series of optimal designs were obtained.The quasi-static and dynamic load carrying capacities of octagonal step by step energy absorbing beam were studied by quasi-static collapse tests and sled impact tests. The optimal octagonal step by step energy absorbing beam was adopted to improve frame crashworthiness and SUV's safety performance. Front impact test results indicated that the deformation mode of octagonal step by step energy absorbing structure was steadier and the variety of acceleration was unobvious, furthermore the octagonal step by step energy absorbing structure could absorb more energy in shorter deformation.The research results showed that the crashworthiness of quadrangular step by step energy absorbing beam and the octagonal step by step energy absorbing beam were good, and the preferable design could be obtained by optimization. The results could be used to be guideline for the design and improvement of the crashworthiness of front rails.