Investigate On Multi-cell Thin-walled Structures Under Axial Collapse And High G Shock

The multiple acceleration or deceleration is sustained by lightweight measurement and control components such as fuzes and photoelectric devices in missile and rocket systems during launch and penetration.The acceleration or deceleration can be as high as tens of thousands or even hundreds of thousands of g(g=9.8 m/s~2).Therefore,the better protection of measurement and control devices in such extreme environments and improving their survival have become key factors in the development of weapon technology.The commonly methods for protecting components such as the circuits of measurement and control devices include reinforcement design and isolation buffer.The internal reinforcement design is restricted by the potting technology and some photoelectric measurement and control devices cannot be potted and reinforced.The reinforcement design also has the problem of low buffer efficiency,so it is particularly important to adopt updated structures for buffering.The foam materials or foam materials to fill single-layer tubes was adopted on the passive buffer protection technology.However,considering the continuous high g impact load in extreme environments,it was difficult to achieve multiple buffer effects by foam strength or foam filling single-layer tubes.Thus,it was urgent to find materials or structures with higher energy absorption efficiency during dynamic impact.Compared with foam materials or foam filled single-layer tubes,the multi-cell thin wall tubes(MT)own the better ability of energy absorption.However,MT and polyurethane foam filled multi cell tubes(FMT)lacked the relevant research on key issues such as dynamic response,energy consumption mechanism and buffer efficiency evaluation.In this paper,the analysis was conducted about the axial crushing mechanical characteristics and high g impact response characteristics of different materials and structural types of MTs in depth.The specific research work was summarized as follows:(1)The MT with Nylon or 6060 aluminum alloy were prepared by using 3D printing method or electrical discharge cutting method,respectively.Quasi-static tensile tests were conducted on nylon and 6060 aluminum alloy materials to obtain the stress-strain curves of these two materials.The dynamic tensile test of 6060 aluminum alloy shows that the strain rate effect is not obvious.Static and dynamic compression experiments were carried out on polyurethane foam(PUR)materials with densities of 0.080 g/cm~3 and 0.180 g/cm~3,respectively.(2)Quasi-static compression experiments were conducted on 6060 aluminum alloy single layer circular tubes(Cir T),MT,and FMT to obtain the load curves,energy absorption(EA),and deformation modes of three different types of thin-walled structures.Based on the theory of Simplified Super Fold Element(SSFE),the SEA of MT was discussed,and the structural coefficients of homeomorphic thin-walled structures were compared and analyzed.The results show that the IPF(Initial Peak Force)under quasi static load is positively correlated with the section length L_c.(3)The dynamic impact experiments were conducted on Cir T,MT,and FMT with 6060aluminum alloy to obtain the load curves and deformation modes of thin-walled structures.The compression displacement was acquired in dynamic impact experiments by using the MATLAB.The load characteristics,energy absorption,coupling effects,and deformation mechanisms of the structure were discussed and analyzed.The strain hardening effect of the material was analyzed using numerical methods.The results show that multicellular can weaken the dynamic reinforcement effect of thin-walled structures,and foam filling can improve the dynamic reinforcement effect of MT.(4)Three typical MTs with Nylon were tested using quasi static compression experiments.The finite element model was calculated based on numerical simulation to obtain the load curve and deformation mode of the structure.The wall thickness,primary and secondary rib plates,and energy absorption of the inner and outer tubes of the structure were analyzed.The polynomial response surface models were constructed.Based on the Non-Dominated Sorting Genetic Algorithm(NSGA-II),the dimensions of two structures with secondary ribs was optimized.The mean crushing force(MCF)formulas for two types of MTs with secondary ribs were constructed using the SSFE theory.The results show that the secondary rib plate can improve the folding deformation of nylon MT and enhance the energy absorption level.(5)The experimental platform of high g impact was conducted and the foam aluminum filled tube and aluminum cone were used as shapers to conduct high g impact tests on Cir T and MT,and the factors affecting the acceleration amplitude of excitation(AAE)were analyzed.Based on the conservation of momentum and energy,the high g impact theory was constructed,which could accurately predict the compression of thin-walled structures during each buffer.Numerical studies were conducted on the cone angle of the shaper,the length of the steel bullet,the impact velocity,and the wall thickness of the thin-walled tube.A polynomial response surface model was constructed,and the AAE and EA were optimized based on NSGA-II.The results show that when the impact speed is to 80 m/s,the AAE of the base can reach 15000 g and can be repeatedly loaded.The dynamic loads,energy absorption characteristics,and excitation acceleration amplitude of multi cell thin-walled structures through dynamic impact experiments and high g impact experiments were obtained and the conclusions could provide technical support for the dynamic buffering of multi cell thin-walled structures.