A Study On The Bending Behavior And Energy Absorption Of Multi-cell Thin-walled Structures Under Transverse Loading

Because of their lightweight,excellent mechanical and energy absorbing properties,multi-cell thin-walled structures are widely used as energy absorbing components in the fields of transportation engineering and safety protection.A large number of theoretical,experimental and numerical studies have demonstrated that multi-cell thin-walled structures have excellent energy absorption capacity and efficiency under axial compression.However,at present,the studies on their transverse bending response are quite few.Some numerical studies show that multi-cell thin-walled beams have excellent energy absorption characteristics under transverse loading,but experimental and theoretical studies on their responses are not found in the open literatures.Based on experimental,theoretical and numerical methods,the bending behavior and energy absorption properties of multi-cell thin-walled tube are studied in this dissertation,which provides theoretical support for the applications of multi-cell thin-walled tubes in practical engineering fields.The main contents of this paper are as follows:(1)The bending responses and energy absorption characteristics of multi-cell beams with two different configurations(partition plates introduced in the axial direction and cross section,respectively)are studied.The nonlinear finite element code LS-DYNA is used to simulate the three-point bending process of the multi-cell tube,and a comparative analysis is carried out between simulation and experiment,which verifies the reliability of the present numerical model.By parametric analysis,the influences of various factors,including the number of partition plates,the conditions of load and the geometric configuration,are studied.The results show that the number of partition plates has a significant effect on the bending performance of multi-cell tubes,but the number of partition plates is not ‘the higher,the better'.A reasonable increase of the diaphragm can effectively improve the energy absorption efficiency of the structure.The optimal configuration of multi cell tubes with different geometric configurations is given,which can help the design of multi-cell tubes subjected to transverse loading.(2)Due to the lack of theoretical models for the bending of multi-cell tubes,two theoretical methods: dimensional analysis and energy analysis,are proposed to analyze and predict the bending responses of multi-cell tubes.Firstly,the bending responses of double cell tubes with different dimensions are studied by numerical simulations.By means of dimensional analysis,the theoretical formula of bending moment related to the ratio of sectional width to thickness,flow stress and bending angle is derived.At the same time,based on the theoretical model of Kecman,the deformation and energy dissipation analysis model of double-cell tubes is established.According to the energy balance of the system and the results of the dimensional analysis,a prediction formula for the bending moment response of double-cell tubes is given.A numerical method is used to simulate the pure bending process of multi-cell tubes,and the simulation results are compared with the two theoretical analysis methods.The numerical simulation results are found to be in good agreement with the theoretical predictions.The above theoretical methods are also suitable for the multi-cell tubes of other sections,and the bending responses of the quaduple-cell tubes are also well predicted as an illustration.(3)Considering the limitation of extruded multi-cell tubes,the bending behavior of an easily fabricated adhesive multi-cell tube is studied by experimental and numerical methods,and the deformation mode and energy absorption property under-three-point bending are analyzed.The experimental results show that the debonding of the adhesive multi-cell tube is related to the structure configurations.When there is no debonding,the performance of the multi-cell tube is basically the same as that of the extruded multi-cell tube.Even if the debonding happens,the energy absorption efficiency of the adhesive multi-cell tube is usually better than that of the constituent single cell tube due to the bonding effect.The three-point bending tests of adhesive multi-cell tubes are simulated by finite element method and the interface of the adhesive multi-cell tube is simulated by three different contact conditions.The calculated deformation mode and load responses are basically consistent with the experimental results.In addition,the energy absorption performances of adhesive multi-cell tubes and foam-filled tubes with the same mass are compared and analyzed.It can be concluded that when there is no obvious debonding,the adhesive multi-cell tubes have similar energy absorption characteristics as extruded multi-cell tubes,together with its good cross-section flexibility and low cost effectiveness.