| Metal thin wall structure is widely used in the structural design of automobile energy absorption box for its excellent mechanical properties and light weight.Its energy absorption characteristics can be improved by improving the structure.In order to break the bottleneck of energy absorption characteristics of traditional thin-walled structures,the introduction of bionic elements for energy absorption structure design has become a research hotspot in recent years.Based on the microscopic structure and fractal principle of bionic beetle coleoptera,this paper proposes three series of bionic multicellular thin-walled circular tubes,and uses finite element method,theoretical analysis and experimental methods to study their energy absorption characteristics,average load prediction expression and optimization design under axial compression.The specific contents are as follows:(1)Carry out the design of bionic beetle coleoptera energy-absorbing structure and research on its energy-absorbing characteristics.Firstly,three series of bionic thin-walled tubes are designed based on the microstructure and fractal principle of beetle’s coleoptera;A6061 sample was prepared and its material properties were obtained by tensile test;The reliability of the finite element model is verified by reproducing literature simulation and quasi-static test,and the appropriate mesh size is determined.Then,LS-DYNA software is used to simulate the quasi-static axial compression of the structure,and the influence of different mass,different branch numbers and different characteristic structures on the energy absorption characteristics and deformation modes of the structure is studied.The results show that the maximum error between the simulation and experimental results is 4.16%;Compared with the traditional rib plate structure,the bionic thin-walled tube can effectively improve the energy absorption characteristics(up to 36.75%);When the number of ribs directly connected to the central small column is 3,the central small column has the best resistance to deformation.(2)Derivation and verification of average load formula of energy-absorbing structure with branch number N=3.Firstly,based on the simplified superposed principle,the energy absorption of thinwalled circular tubes is divided into two parts: bending deformation energy and membrane deformation energy.Then,according to the structural characteristics,the energy absorption of the bionic thin-walled tube is divided into four parts,including the bending deformation energy,the membrane deformation energy of the circular element,the circular element,and the rib plate element.The basic folding element is analyzed using the law of energy conservation and the principle of minimum energy.Further,theoretical derivation is conducted based on the number of basic elements to analyze the impact of structural parameters on energy absorption characteristics.Finally,the accuracy of the proposed average load formula is verified using finite element analysis.The theoretical calculation results and simulation results agree well,with a maximum error of 9.56%.(3)Carry out the research on energy absorption characteristics and optimization design of multi-cellular porous thin-walled conical tube.Firstly,based on the numerical simulation results of the bionic thin-walled tube and the design criteria of the automotive energy absorbing box,the bionic multicellular thin-walled tube with t of 0.8mm～2mm and d of 8mm～20mm was selected for optimization design research,in order to obtain the bionic thin-walled structure size with the optimal energy absorbing characteristics.Then,based on the optimal multicell thin-walled tube,the Pareto front is used to provide a set of optimal solutions under axial compression,providing guidance for engineering design.The results show that compared with the traditional rib plate structure,the optimal bionic thin-walled tube has a 45.50% increase in specific energy absorption and an 18.54% decrease in initial peak load;... |
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