Theoretical Models Of The Deformation And Energy Absorption Of The Circular Tubes Under Axial Compression Over Die

In collision,energy absorption structure protects people and important component by dissipating impact energy.The large plastic deformation and ductile fracture of the thin-walled metal structure are the major mechanisms to absorb impact energy because they are able to absorb considerable energy irreversibly with low weight.Compared with other deformations,expansion,shrink and inversion of circular tube under axial compression of the die are used widely for high Specific Energy Absorption(SEA),steady compression force without peak,insensitivity to load.It is important to understand and optimize the energy absorption of deformation of the circular tube in the impact protection.In this thesis,the theoretical models for the expansion,shrink and inversion of tube are established and validated by the experiments and simulations.And the principles to the design energy absorption structure of this type is given.The main contents and the conclusions are as follows:(1)The theoretical model of the metal tube expansion is proposed.The model is deduced based on the arc deformation profile;the critical die radius is defined and the deformation of the tube is classified into three modes;the theoretical model is validated by the previous models,the experiments and the numerical simulations,and the results show that the current model has higher accuracy and wider applicability.(2)The theoretical model of the metal tube shrink is proposed.The model is deduced based on the arc deformation profile,and validated by the experiments and simulations.The results show the current model has high accuracy and wide applicability;The energy dissipated is classified into different deformation mechanisms,and the classification is validated by the simulations.(3)The theoretical model of the metal tube inversion is proposed.The basic model is deduced based on the assumption of the linear distributed curvature;the energy dissipation in the meridional direction is obtained by the equilibrium,and introduced into theory to refine the basic model;the current model is validated by the experiment and the simulations,and it is found to be accurate and widely applicable.