Research On Energy Absorption Mechanism And Design Method Of Bionic Multi-Cell Thin-Walled Structures

In recent years,with the gradual increase of car parc in our country,the occurrence of traffic accidents has become more and more frequent.Car travel not only brings convenience to people,but also poses a great threat to t heir lives and property.Therefore,the research on the crashworthiness design of the body structure has become a key topic at present.At the same time,the rapid development of new energy vehicles has put forward higher requirements for the lightweight of the body,which is also a great challenge to the crashworthiness design of the body structure.Metal thin-walled structures are widely used in body structure design due to their excellent energy absorption properties.However,the existing metal thin-walled structures have shortcomings such as low energy absorption efficiency and poor load stability.To further improve their energy absorption capacity,in-depth analysis of their energy absorption mechanism reveals the key factors affecting its energy absorption capacity and proposes corresponding designs guidelines are imperative.In addition,the design of the existing thin-walled structure mostly relies on the experience of the designer,and the design efficiency is low.After thousands of years of evolution,natural biological structures have excellent load bearing capacity,and the bionic design of natural biological structures can greatly improve the design efficiency.Therefore,bionic design has become a research hot spot in various engineering application fields in recent years.In this paper,through the biomimetic design of the macroscopic and microscopic characteristics of natural biological structures,four novel design methods of biomimetic multi-cell thin-walled structures are proposed,and their energy absorption mechanism and crashworthiness performance are systematically studied.The main research focuses and innovations are as follows:(1)By analyzing the energy absorption mechanism of thin-walled energyabsorbing structures,the design criteria of multi-cell thin-walled structures are proposed.Firstly,based on the simplified super folding element theory and the constituent element method,the energy absorption mechanism of the multi-cell thin-walled structure was deeply analyzed and the key factors affecting its energy absorption capacity were revealed.Then,the design guidelines of the multi-cell thin-walled structure was further proposed.The analysis of the energy absorption mechanism of thin-walled structures can reveal the essence of its energy absorption behavior,so as to further explore its energy absorption potential,which is of great significance for improving the design efficiency of multi-cell thin-walled structures,and also for further research on bionic multicellular structures.The research provides theoretical guidance on the design method of thin-walled structures.(2)Inspired by the structural characteristics of lotus leaf veins,a design method of bionic lotus leaf multi-cell thin-walled circular tubes is proposed.Firstly,according to the bifurcation structure of the lotus leaf vein,a bionic lotus leaf multi-cell tube is proposed and the corresponding finite element model is established.The accuracy and reliability of the finite element model are verified by quasi-static compression test of the bionic lotus leaf multicellular tube specimen.The test results are in good agreement with the simulation results.Based on the simplified super folding element theory,the theoretical models of the mean crushing force and specific energy absorption of the bionic lotus multi-cell tube were deduced.And the energy absorption mechanism was revealed based on the obtained theoretical model.Furthermore,the effects of the cross-sectional geometric parameters of the bionic lotus multicell tube on its crashworthiness was studied through the established finite element model;the optimal cross-sectional parameter configuration was obtained through multi-objective optimization of the bionic lotus multi-cell tube.The research results show that the bionic lotus multi-cell tube has better crashworthiness performance than that of the traditional multi-cell thin-walled tube.(3)Inspired by the biological evolution law of plant stems,a design method of bionic gradient multi-cell thin-walled structure is proposed.Firstly,a bionic gradient multi-cell thin-walled structure was proposed by structural biomimetic of the gradient features highlighted in the evolution of plant stems.Then,the theoretical prediction model of the mean crushing force and specific energy absorption of the bionic gradient multi-cell thin-walled tube was deduced based on the simplified super folding element theory.And its energy absorption mechanism was revealed.Furthermore,the finite element model of the bionic gradient multi-cell thin-walled tube was established,and the corresponding quasi-static compression test was carried out to verify the reliability of the established finite element model.The results show that the simulation results of the bionic gradient multi-cell thin-walled tube are basically consistent with the experimental test results.The effects of key geometric parameters on the crashworthiness of the bionic gradient multi-cell thin-walled tube was further studied,and the results showed that the number of layers and wall thickness had a significant effects.The accuracy of the theoretical prediction model of the mean crushing force and specific energy absorption of the bionic gradient multi-cell thin-walled tube is effectively verified by comparing with the simulation results.Compared with the traditional multi-cell circular tube,the bionic gradient multi-cell thin-walled tube has greatly improved crashworthiness performance.This study provides a good reference for the crashworthiness design of the multi-cell thin-walled structure.(4)Inspired by the bionic hierarchical structure,a design method of a vertex-based hierarchical multi-cell square tube is proposed.Firstly,a novel multi-cell square tube is proposed by changing the connection mode of the cells of the conventional multi-cell square tube,and then a vertex-based hierarchical multi-cellular square tube is proposed.Then,the theoretical prediction models of the mean crushing force and specific energy absorption are derived based on the simplified super folding element theory.Based on the theoretical prediction model,the crashworthiness advantages of the novel multi-cell square tube and the vertex-based hierarchical multi-cell square tube are revealed by compared with the corresponding traditional multi-cell square tube.Furthermore,the finite element models of the novel multi-cell square tube and the vertex-based hierarchical multi-cell square tube are established and the model accuracy is verified by experiments.Then,the deformation mode and energy absorption mechanism of the novel multi-cell square tube and the vertex-based hierarchical multi-cell square tube are compared with the corresponding traditional multi-cell square tube from the point of simulation.The results show that both theoretical and simulation analysis results strongly prove that the proposed cross-section configuration method of multi-cell square tube is more efficient than that of traditional method,and the vertex-based hierarchical multi-cell square tube is an efficient energy-absorbing thin-walled structure.(5)Inspired by the bionic hierarchical structures,an design method of the edge-based hierarchical multi-cell square tubes is proposed.First,the finite element model of the edge-based hierarchical multi-cell square tube is established and verified by experiments.The simulation results are in good agreement with the experimental results,and the finite element model is effectively verified.Further,the crashworthiness performance of the edge-based hierarchical multi-cell square tube was studied with the established finite element model,and the effects of the hierarchical level on the crashworthiness of the edge-based hierarchical multi-cell square tube was studied.Compared with the traditional multi-cell square tube,the crashworthiness performance of the edge-based hierarchical multi-cell square tube has been greatly improved,and the hierarchical level has a significant effect on the energy absorption efficiency of the edge-based hierarchical multi-cell square tube.Finally,the theoretical prediction model of the mean crushing force and specific energy absorption of the edge-based hierarchical multi-cell square tube is deduced based on the simplified super folding element theory.Based on the theoretical prediction model,the energy absorption characteristics of the edge-based hierarchical multi-cell square tube were theoretically analyzed,and the energy absorption mechanism and energy absorption advantages of the edge-based hierarchical multi-cell square tube were revealed from the theoretical point of view.The research results show that the introduction of the bionic hierarchical structure significantly improves the crashworthiness of the multicell thin-walled square tube.In this paper,four biomimetic multicellular thin-walled energy-absorbing structures are proposed based on the bionics of the macro and microscopic features of natural biological structures,which have been proved to have excellent crashworthiness performance.These bionic multi-cell thin-walled structures can be applied to the design and development of the front longitudinal beams and bottom cross beams of new energy vehicles,and play an important role in reducing the damage of occupants in frontal collisions of vehicles.At the same time,the research in this paper also has important reference significance for the in-depth application of the bionic design method in the structural crashworthiness design.