Dynamic Response Of Graded Thin-walled Circular Tubes Under Axial Impact Loading

As a common energy absorbing structure,thin-walled tubes has been widely applied in the fields related to safety such as vehicle safety,construction engineering and so on.The thin-walled tubes is relatively stability in the aspect of structure,its crushing mode is regular for the fold buckling deformation under axial impact loading,and the buckling compaction energy absorption is controlled.Researches on the buckling deformation behavior of the thin-walled tubes under axial load emerged from 1960 s,but most of these studies are analysis theory and experiments study on the fold deformation of uniform thin-walled circular tube.The dynamic response behavior of graded thin-walled circular was rarely mentioned.In recent years,a large number of studies on the shock wave model in the process of axial impact of foam materials provide a new idea for the establishment of the research model of the dynamic response of thin-walled circular tubes under axial impact load.Based on the dynamic buckling deformation of the uniform thin-walled circular tube,the shock wave model is applied to analyze the buckling deformation process of the thin walled circular tubes under axial impact,and analyzed the dynamic response and energy absorption of the structure.Fitting of the theoretical model and the finite element simulation results shows that directly using the initial thickness of thin-walled tube are not good predictors of the velocity time duration characters of the additional weight in the process of impact velocity.Through fixing the thickness of the round wall in model to its wall thickness of actual compaction process in the buckling deformation,the theoretical model and the finite elementsimulation results are fitted well.This proves that the modified shock wave model can better predict the axial dynamic load dynamic response of thin walled tube.On the basis of the shock wave model of uniform wall tube,a gradient tube with constant external diameter and varied wall thickness presented in this paper.When the weak side of the gradient tube and impact end are the same side,the buckling in the process will be generated from the impact end;otherwise,the buckling produced from both sides of tube.This paper carries on theoretical derivation and finite element simulation for these two conditions respectively,and analyzed the effect of mass ratio,thickness-radial ratio and the gradient parameters on the structural energy absorption characters.Following conclusions are got: the use of shock wave model can better predict the axial dynamic response and the energy absorption of the uniform and gradient thin-walled tubes;energy absorption capacity of gradient tube are better than that of the uniform circular tube,and the structural energy absorption capacity increased with the increasing of the thickness difference of the two ends of tubes.