Crashworthiness Analysis And Optimization Design Of Automobile Energy-absorbing Components Based On Negative Poisson’s Ratio Structure

Energy-absorbing box is the main energy-absorbing component in vehicle front-end collision.Therefore,it is of great significance to study the structure of energy-absorbing box with good energy-absorbing effect to improve the safety performance of vehicle front-end collision and reduce the cost of vehicle maintenance.The Negative Poisson ’s Ratio(NPR)structure not only has the characteristics of light weight,good impact resistance and shear resistance,but also has the ’expansion effect ’,which is widely used in automobiles,ships,aerospace and medical fields.In this paper,different thin-walled energy-absorbing structures are studied,and combined with the three-dimensional(3D)double-arrow NPR structure,an energy-absorbing structure with better crashworthiness is designed and applied to the front end of the bus as an energy-absorbing box.The main research contents of this paper are as follows:(1)Combined with the theoretical analysis method,the equivalent static mechanical properties of the 3D double-arrow NPR structure are analyzed.The influence of the cell parameters of the 3D double-arrow NPR structure on the relative density,equivalent Poisson ’s ratio and equivalent elastic modulus is explored.The simulation analysis and sample test verify that the 3D double-arrow NPR structure designed in this paper has a good negative Poisson ’s ratio effect.(2)Based on the traditional cylindrical thin-walled energy-absorbing structure,the stepped energy-absorbing structure is introduced.Combined with the 3D double-arrow NPR structure,under the seven cross-section shapes of triangle,quadrilateral,pentagon,hexagon,heptagon,octagon and circle,the finite element models of four different energy-absorbing structures,such as cylindrical energy-absorbing structure,stepped energy-absorbing structure,cylindrical energy-absorbing structure filled with NPR structure and stepped energy-absorbing structure filled with NPR structure,are established respectively.Under the condition of frontal impact,the influence of section shape change on the crashworthiness of four different energy absorbing structures is studied respectively,and the deformation mode is analyzed.On this basis,the influence of the filling of the NPR inner core on the crashworthiness of different energyabsorbing structures is analyzed.The results show that for different energy-absorbing structures,the thin-walled shell and the filled inner core will have a coupling effect during the frontal collision process,so that the filled energy-absorbing structure has an energy-absorbing coupling enhancement effect,which significantly improves the crashworthiness of the overall structure.Because the energy-absorbing structure designed in this paper is applied to the automobile energy-absorbing box,considering that there are many non-frontal impact conditions in the actual collision process of the front end of the automobile,the energy-absorbing structure with better crashworthiness in the above analysis is used.Under the multi-angle impact condition,the TOPSIS decision method is used to select the energy-absorbing structure scheme with the best comprehensive performance evaluation index.(3)Under the multi-angle impact condition,the effects of the step angle of the shell of the energy absorbing structure and the cell width and cell thickness of the filled inner core on the crashworthiness of the filled energy absorbing structure were studied respectively.Based on the principle of functional gradient,a mid-core enhanced filled inner core is proposed on the basis of the traditional gradient thickness filled inner core.The crashworthiness analysis is carried out under multi-angle working conditions.The results show that the energy-absorbing structure filled with mid-core enhanced inner core has better crashworthiness.(4)The multi-objective optimization design of the filled energy-absorbing structure with better crashworthiness is carried out.The optimal Latin hypercube experimental design method is used to establish the approximate model of each crashworthiness evaluation index of the filled energy-absorbing structure based on the second-order polynomial response surface model method.On this basis,the NSGA-II algorithm is used to optimize the design.The results show that compared with the stepped energy absorption structure and the unoptimized energy absorption structure,the optimized energy absorption structure has good comprehensive anticollision performance.Finally,the optimized energy-absorbing structure is arranged as an energy-absorbing box at the front end of a bus,and the simulation is carried out under the condition of frontal low-speed collision.The results show that the optimized energy-absorbing structure has a stable and good energy-absorbing effect during the collision of the bus,which can effectively reduce the energy absorption of other components and reduce the deformation of the bus during the collision process,thus ensuring the safety of the occupants in the vehicle.