轴向压溃下多胞薄壁结构的吸能特性研究

Study on Energy Absorption Characteristics of Multi-cell Thin-walled Structure under Axial Crushing

为了研究截面拓扑构型对薄壁结构吸能效果的影响,设计出耐撞性能较优的结构。首先,在单胞薄壁结构的基础上,通过添加正交肋板得到四胞薄壁结构,并进一步设计出内接方形、圆形、菱形、六边形和八边形的五胞薄壁结构。然后,建立了准静态轴向压溃有限元仿真模型,以总吸能量、比吸能、峰值压溃力、平均压溃力和压溃力效率作为评价多胞薄壁结构耐撞性能的指标,通过有限元仿真试验得出五胞管薄壁结构具有较优的吸能特性。随后,从理论预测的角度出发,研究薄壁结构的基础角单元变形模式,运用简化超折叠单元(SSFE)理论推导出多胞薄壁结构的平均压溃力理论公式,与有限元仿真结果对比显示误差能够控制在±6%以内,具有较好的一致性。最后,以结构壁厚和内接形状的大小作为设计变量,以比吸能和峰值压溃力作为优化目标,采用全因子试验设计方法建立了近似代理模型,运用第二代非支配排序遗传算法(NSGA-Ⅱ)对多胞结构进行了多目标优化设计,得到4种结构的Pareto解集。结果表明:针对峰值压溃力要求为20 kN以下的薄壁结构,4种结构相比于单胞薄壁结构的比吸能均增加了50%左右,经多目标优化设计后的多胞薄壁结构耐撞性能得到了明显的提升。

In order to study the influence of cross-section topological configuration on energy absorption effect of thin-walled structure,the structures with better crashworthiness are designed.First,on the basis of singlecell thin-walled structure,the four-cell thin-walled structure is obtained by adding orthogonal ribs,and the five-cell thin-walled structures with inscribed square,circle,diamond,hexagon and octagon are further designed.Then,the quasi-static axial crushing finite element simulation model is established.Taking total energy absorption,specific energy absorption,peak crushing force,mean crushing force and crushing force efficiency as the indicators for evaluating crashworthiness of multi-cell thin-walled structures,it is verified that the five-cell thin-walled structure has better energy absorption characteristics by using finite element simulation test.Subsequently,from the perspective of theoretical prediction,the deformation mode of basic angular unit with thin-walled structure is studied,the theoretical formula of mean crushing force of multi-cell thin-walled structure is derived by using simplified super folding element(SSFE)theory,and the error can be controlled within±6%compared with the result obtained by finite element simulation,which has good consistency.Finally,an approximate proxy model is established by using a full-factor experimental design method with the structural wall thickness and the size of the inscribed shape as the design variables,and with specific energy absorption and peak crushing force as the optimization objectives.Multi-objective optimization design of multi-cell structure is conducted by using the second generation of non-dominated sorting genetic algorithm(NSGA-Ⅱ),and the Pareto solution set with 4 types of structure is obtained.The result shows that for thin-walled structure with peak crushing force requirement of less than 20 kN,the specific energy absorptions of the 4 types of structure are all 50%higher than that of single-cell thin-walled structure,and the crashworthiness of multi-cell thin-walled structure with multi-objective optimization design is improved significantly.