Oblique Crashworthiness Study And Optimization Of Multi-cell Filled Thin-walled Tubes

When a car crashes,the body structures absorb energy by deformation,in which the front longitudinal beams are the main component of energy absorption structures.Traffic accidents take various form,Small angle oblique collision is a common form of traffic accidents..Therefore,it is important to study the crashworthiness of the front longitudinal beam under oblique impact for vehicle safety.Thin-walled structures are usually used as simplified forms of front longitudinal beam for crashworthiness analysis,so this paper takes thin-walled tube as the research object.Firstly,negative poisson's ratio(NPR)structure is used as filling cells,the crashworthiness of NPR cells filled thin-walled tube and empty thin-walled tube is analyzed and compared.Secondly,the material properties,placement method,concave direction,cell density and structural parameters of NPR structure are studied for the influence on the tube crashworthiness.Thirdly,a gradient section NPR filled thin-walled tube is proposed and compared with the equal section NPR filled thin-walled tube.It is found that the oblique crashworthiness of the gradient section NPR filled thin-walled tube is better than the one with equal section.Besides,for non-filled thin-walled tubes,four kinds of polygonal multi-cell tapered tubes are proposed.The Crashworthiness of four kinds of hexagonal multi-cell tapered tubes under different load angles is analyzed and compared.It is found that the hexagonal tapered tube with six cells have the best crashworthiness.The effects of the section size,taper angle and wall thickness of the tube on the oblique crashworthiness are studied.Finally,the structural parameters of polygonal multi-cell tapered tube are optimized by using proxy model technology.Taking the maximum specific energy absorption and the minimum peak crash force as the design objectives,and taking section size,taper angle and wall thickness of the tube as design variables,the Pareto sets of the structural optimization problem under multiple load angles is obtained.The results show that the crashworthiness of thin-walled tubes can be effectively improved by NPR structure and polygonal multi-cell tapered structure.Structural parameters have a great influence on the crashworthiness of thin-walled tubes.The two crashworthiness evaluating indicators can not be improved synergistically.The multi-objective optimization can significantly improve the crashworthiness of polygonal multi-cell tapered tubes.Moreover,the Pareto set is different under different load angles and different weight allocation schemes.