Design And Optimization Of Buckling Mode Of Tubular Members

Under the action of axial force,different forms of buckling modes occur in tubular members due to different factors such as slenderness ratio,diameter-thickness ratio,and cross-sectional shape.When slenderness is large,the members are prone to be low-order overall flexural buckling.When the members undergo low-order buckling,their bearing capacity is greatly reduced,which seriously affects the safety of the structure.In addition,the members only form plastic zones in the middle,and the energy dissipation capability is poor.In this paper,the origami concept is introduced into the common square tube to change the geometric configuration of the member,so that the symmetrical axial buckling mode can also occur for the members with larger slenderness,and the energy dissipation capacity of the member can be enhanced.The influence of various origami configurations on the buckling mode of the tubular members was studied as well as its mechanical properties under axial unidirectional loading and cyclic repeated loading.In order to increase the energy dissipation capacity of ordinary square tubes,a rigid Miura origami configuration is introduced into the tubular member to form a rigid origami tubular member.The influence of cross section length a,parallelogram angle ?,plate thickness t,and crease weakening degree factor ? on the buckling mode of members is studied.The results show that the larger the side length a is,the easier the axial buckling mode of the member would be;The greater the parallelogram angle ?,the plate thickness t,the degree of crease weakening factor ? is,the greater the axial stiffness of the member would be and the more prone to the out-of-plane bending buckling mode.Moreover,when the length a of the cross-section not less than 150 mm,the degree of weakening of the crease not greater than 0.8,the thickness not more than 12 mm,and the angle ? between the parallelograms not more than 60°,the buckling mode of the member is mainly the axial buckling mode.Through the above study,it is found that deformation of paper folding unit at the boundary is smaller under the constraint conditions while the deformation at the middle unit is larger.The crease thickness and geometric dimensions of a typical unit are two major factors affecting the rigidity of the origami unit.In this paper,the effect of the thickness distribution of a typical unit with a side length of 200 mm,a plate thickness of 10 mm and an angle of parallelogram of 65° on the buckling mode of the member is studied.It is concluded that the greater the decrease in crease thickness attenuation value ?,the smaller the bearing capacity of the member and it would mainly be the mode of axial flexion;The influence of the distribution of angles of parallelograms on the buckling mode of a typical unit with a side length of 200 mm,a plate thickness of 10 mm,and an unweakened fold is also studied.It shows that when the gradient difference ?of the parallelogram angle is larger,the stiffness of the typical unit at both ends would be smaller,and the axial buckling modes of the two ends would be in the main.Unlike rigid origami configurations,non-rigid origami is a stable structure after determining geometric parameters.Non-rigid origami-shaped tubular members have higher axial stiffness.Among three typical origami models(pyramid model,crash-box model and triangular six-fold crease model),the triangle six-crease model was selected for the study.Parameters such as section shape,side length,relative section angle,and plate thickness were analyzed.The greater the relative rotation angle of the section is,the smaller the axial stiffness of the member would be and the more prone to the axial buckling mode;The larger the section side length a,the larger the slenderness ratio of the member and the less likely the bending buckling mode to occur;The greater the plate thickness is,the smaller the axial stiffness would be and more bearing capacity the members would have.However,when the thickness of the plate is greater than a certain limit,a lower order bending buckling mode would also occur.