Crashworthiness Simulation And Optimization Of Octagon Thin-Walled Structures

As effective absorbers,the thin-walled structures have been widely used in automotive crashworthiness design.It is a significant task for protection of passenger safety to design light and efficient energy absorbing devices with excellent crashworthiness.In present work,a series of research work was carried out in order to improve the structural crashworthiness and energy absorption characteristics of thin-walled metal structures.With a deep research on the basic of deformation modes and energy absorption,three new types of octagon thin-walled structures with good performance were proposed,and its energy absorption characteristics and crashworthiness were analyzed and optimization designed numerically,experimentally and theoretically.The main contents of this paper are as follows:(1)The main deformation modes of thin-walled metal structures were introduced.The deformation modes of octagon multi-cell thin-walled tubes were simulated and the energy absorption principle of the tubes had been carried based on the theoretical analysis by dividing the profile into several typical parts.(2)The energy absorption characteristics of the octagon multi-cell thin-walled tubes under quasi-static axial loading were simulated using finite element software ABAQUS.The effects of cross sections shape and structural parameters on energy absorption characteristics of the multi-cell tubes were analyzed.Based on Super Folding Element theory and constituent elements method,the energy absorption of the tubes under axial crushing was theoretically analyzed.According to indicator of the energy absorption characteristics,side to side distribution of the octagon multi-cell tubes(S2S)were optimized using the non-dominated sorting genetic algorithm.The results show that the energy absorption characteristics of the side to side distribution is better than the corner to corner distribution,and the octagon multi-cell S2S tubes is optimal;and structural parameters influence its energy absorption characteristics significantly.The analytical prediction results show a good agreement with the numerical results.The octagon multi-cell S2S tubes optimized has better energy absorption characteristics;the specific energy absorption is increased by 33.11%,and the peak crushing force is reduced by 3.78%.(3)The effects of impact angles and structural parameters on the crashworthiness of the octagon sandwich thin-walled tubes were analyzed,and the dynamic responses and energy absorption of sandwich thin-walled tubes under the oblique impact loading conditions were studied by using multi-objective optimization method.The results show that the impact angles and structural parameters significantly influence its crashworthiness;the optimal configuration parameters of the sandwich thin-walled tubes are different under different impact angles.The weighting factor for different load angles is critical on the crashworthiness optimization of the sandwich thin-walled tubes for multiple oblique load cases;the study will provide a guideline for design of energy absorber under multiple oblique loading.(4)In order to improve the safety of buses under frontal impact,the energy-absorbing structures were added to the buses to absorb more crash energy,thereby reducing the values of acceleration and deformation of the driver’s cabin.A new octagon combination structure was used in the front of buses,the energy absorption characteristics of octagon combination structure on frontal impact were studied by sled test.The results show that the support device having sufficient strength and can be used to support the octagon combination structure;the frontal impact energy can be absorbed better and the initial peak acceleration can be reduced effectively by the structure made of material A16063.The octagon combination structure can improve the impact security of bus.