Design And Experimental Study Of Composite Negative Stiffness Structures And Mechanical Properties

In recent years,negative stiffness structures have been widely used in vibration control,energy absorption,shock buffering,motion control and other fields.However,in view of the increasingly complex service conditions,the existing structures with negative stiffness characteristics only under compression load or a single working condition can not meet the increasing application requirements,which directly hinders its application.In order to solve the above problems,on the basis of existing research,three kinds of composite negative stiffness structures are proposed in this paper,and their performance is studied through theoretical analysis,simulation analysis,optimization design,experimental analysis and other ways.Specific research contents are as follows:Firstly,based on the theory of correlative curved beam design,three kinds of composite negative stiffness structures are proposed,which are bidirectional tensile negative stiffness structure,bidirectional torsional negative stiffness structure and bidirectional tension-torsional negative stiffness structure.Three kinds of composite negative stiffness structures are studied theoretically and optimized.The results show that the bidirectional negative stiffness structures have negative stiffness characteristics in both tensile and compressive directions.The bidirectional torsional negative stiffness structure has two negative stiffness characteristics: active torsional and passive torsional.The bidirectional tension-compressive-torsional negative stiffness structure has the negative stiffness characteristics of both tensile and torsional loading directions,which can realize the negative stiffness effect under compound working conditions.Then the finite element analysis model of the composite negative stiffness structure was established by optimizing the base material and obtaining the mechanical property parameters.The finite element method is used to analyze three kinds of composite structures with negative stiffness under complex load.The correlation between key structural parameters and mechanical properties of composite structures with negative stiffness was obtained.The influence law of the number difference of curved beams on the performance of bidirectional tension-compressive-torsional negative stiffness structure is studied,which provides reference for the selection of key parameters of bidirectional tension-compressive-torsional negative stiffness structure.Finally,three kinds of composite negative stiffness structures were fabricated by additive manufacturing technology,and the complex load test was carried out on the three kinds of composite negative stiffness structures.The two-way tensile and compression negative stiffness structures were tested.Two torsional directions of negative stiffness structure were tested.The two load directions of tensile and torsional negative stiffness structures were tested.The experimental results are compared with the simulation results.The results show that the three composite structures with negative stiffness all have stable energy absorption function.Their experimental curve is basically consistent with the simulation curve.For the three composite structures with negative stiffness,the load threshold increases with the increase of the beam thickness and the increase of the beam height.In the test curve of bidirectional tensile negative stiffness structure,the load threshold under compression load is greater than that under tensile load.Finally,cyclic loading and unloading tests were carried out for three kinds of composite structures with negative stiffness.After ten cyclic loading and unloading tests,the load threshold of the three composite structures with negative stiffness changes little.In conclusion,the three composite structures with negative stiffness all have negative stiffness characteristics and reusability under complex loads.The research work of this paper enriches the negative stiffness structure,makes up the design blank of the existing negative stiffness structure for the compound load condition,which provides theoretical and experimental support for the design and application of negative stiffness structure under complex service condition.