Torsional Buckling Analysis And Bistable Design Of Thin Pre-twisted Strip

The thin pre-twisted strip structures are often used as blades for large industrial equipment such as aircraft engines,wind turbines equipment such as aircraft engines,wind turbines and so on.Previous studies have shown that the structure exhibits special mechanical characteristics due to its special geometry.In this paper,the governing equations for the buckling of thin pre-twisted strip are derived and the analytical expressions for the critical buckling load of torsion on both ends simply supported and both sides free are solved.Secondly,The jumping characteristics of torsional postbuckling are studied and the influence of different design parameters on the torsional jump characteristics of structures is discussed.Finally,three kinds of twisted bistable structures are proposed by using the jumping characteristics of torsion post buckling and by changing their topology.(1)Analytical solution for the torsional buckling of the thin pre-twisted strip.The static linear solution and nonlinear solution of the strip plate with both ends simply supported and the other two free conditions are derived by using the theoretical method.the linear solution is taken as the internal force expression,and the governing equation of the buckling of the strip is deduced by using the equilibrium method.An analytical expression for the torsional critical buckling of the thin pre-twisted strip is obtained by the inverse method.The correctness of the static linear solution is verified by comparing with the finite element analysis results.When the load smaller,compared the linear solution with nonlinear solution,the rationality of the linear solution is verified.The validity of the analytical solution is verified by comparing with the numerical results.(2)Study on the jumping characteristics of the thin pre-twisted plate subjected to torsion postbuckling.The postbuckling characteristics of structures are mainly studied by numerical analysis.The load displacement curve shows that the structure has a sudden torsional jump behavior after torsional buckling,with the increase of the displacement load,the reaction force suddenly decreases greatly.Then the effects of different geometric parameters,material properties,structural shapes and topological configurations on the torsional jumping performance of structures are also discussed.The results show that the torsional jump characteristics after torsional buckling are adjustable,and reasonable design is expected to achieve bistable characteristics.(3)Design and analysis of the novel twisted bistable structures.Based on the influence of the design parameters on the torsion jumping characteristics of the thin pre-twisted strip structures,three different types of twisted bistable structures are designed: pre-twisted beam structure,pre-twisted wing frame structure and pre-twisted stiffened plate structure.Their bistable characteristics are confirmed by postbuckling analysis of three types of structures under torsional loading.It is proved that the bistable structure is repeatable by analyzing the continuous jump between two steady states.The effects of pre-twist angle,aspect ratio and material properties on the jump characteristics of bistable configuration are discussed and the influence of different parameters on each kind of bistable structures is obtained.