Design And Mechanical Properties Of Structure With Negative Stiffness On A New Type Of Friction Energy Dissipation

Negative stiffness metamaterials have unique deformation mechanisms and mechanical responses,such as reusability,jump properties,multi-steady state properties,etc.,which are different from common lightweight structures/materials(hard foam,honeycomb,lattice).Because of these characteristics,this kind of metamaterials show some unique advantages that other structures do not have in such aspects as energy absorption buffer,vibration reduction and noise reduction,so it has a broad application prospect.However,due to structural characteristics and deformation mechanism,the stiffness and strength of traditional negative stiffness metamaterials are much lower than that of common lightweight structures,which limits their application to a large extent.In order to solve this problem,a new type of friction-resistance negative stiffness structure is proposed in this paper.Compared with the traditional curved beam negative stiffness structure,it has a good bearing capacity,while retaining or even strengthening its advantages(reusability,series,no reflexibility,etc.).Compared with the existing friction-resistance negative stiffness structure,it also has good continuity,which makes the structure more widely used.In this paper,a single material structure,a composite structure and a new type of friction-resistive negative stiffness structure were designed and prepared successively,and a complete theoretical,finite element and experimental system was established to characterize and evaluate the performance of various structures.The main research contents are as follows:Single material structure: six kinds of single material structure with different parameters are designed firstly.The main design parameters are the number of rings and the length of rings.Using nylon as the base material,the structure was prepared by melt deposition(FDM)technology,and the modulus of the material was measured.Secondly,the flat-pressing experimental simulation of the single material structure with six parameters was carried out by using the finite element software.Among them,three parameters of the structure exceeded the elastic strain limit of the material and were not considered in the future.The compression-unloading method is used to verify the correctness of the numerical model.Finally,cyclic load-unloading experiments are carried out to verify the structure's good reusability.2.Compound structure: on the basis of single material structure,in order to further improve the mechanical properties of the whole structure,the compound structure was prepared by adding silica gel.It can be observed that there is a gradient in the strain distribution and the maximum strain appears at both ends of the uppermost ring by using the finite element software to simulate the flat compression experiments of the structures with three parameters.In the experiment,we first compare the single material structure with the composite structure,and find that the composite effect of 1+1 >2 is produced,which reflects the value of the composite structure.Secondly,the structural parameters that best meet our design requirements are found through the flat pressure experiment,which can be used for the subsequent design of internal teeth.Finally,cyclic load-unloading experiments are carried out to verify the structure's good reusability.3.New friction resistance type negative stiffness structure: friction resistance type negative stiffness structure is further based on the compound structure of the tooth design to get,the main design parameters of tooth height and convex tooth Angle.Firstly,four kinds of friction-resistance negative stiffness structures with different parameters were designed and fabricated.The choice of base material and preparation method were the same as the composite structure.In the aspect of finite element,the flat compression experiment was carried out on the finite element model.At the same time,the energy dissipated was calculated through the load-displacement curve in the compression process and the comparative analysis was carried out.The results show that when the tooth Angle is constant,the higher the tooth height,the smaller the maximum principal strain.When the tooth is higher,the tooth Angle is closer to 45°,and the maximum principal strain is smaller.Finally,we compare the theory,simulation and experiment,and find that the curve trend is consistent.In terms of experiments,the structure parameters with the strongest bearing capacity and the best energy dissipation effect were obtained by compressing and unloading the structure.Finally,the impact test of the friction-type negative stiffness structure shows that the friction-type negative stiffness structure has more prominent advantages in cushioning and shock absorption.Finally,the reusability of the frictional negative stiffness structure was verified by cyclic load-unloading experiments.