Study On The Design And Energy Absorption Mechanism In Tailored Multi-stable/Mono-stable Structure

Negative stiffness(NS)metamaterials can be divided into two types: multi-stable and mono-stable.Multi-stable metamaterials can use the multistability characteristics to trap the work force in the structure and avoid secondary damage effectively,but it needs extra force to recover to the original shape when repeated use.Mono-stable metamaterials can meet the requirement of shock isolation and repeatable energy absorption,while it can't achieve the function of trapping energy.Therefore,it is necessary to study a tailored multi-stable / mono-stable NS metamaterials with high mechanical performance,then make a structure with both trapping energy mode and repeatable energy absorption mode.In this paper,a new kind of multifunctional NS metamaterial was proposed,which can be tailored as multi-stable or mono-stable.The structural design,parameter influence and energy absorption performance were studied systematically.It mainly includes the following aspects:Firstly,based on the bistability principle of beam,a new kind of multifunctional NS metamaterial was designed,which can realize the function of tailored multi-stable /mono-stable.The new kind of conical multifunctional NS metamaterial was manufactured by FDM(fused deposition modeling)3D printing technology,which composed of soft and hard materials.Through the quasi-static compression tests and numerical simulation,the function of tailored multi-stable / mono-stable was verified.Secondly,through using the finite element model method,the influence of geometrical parameters on the function of tailored multi-stable / mono-stable was systematically studied.From the aspects of tilt angle,slenderness ratio,the ratio of offset distance and load capability gradient,determined the scope of geometrical parameter to realize the function of tailored multi-stable / mono-stable.Finally,through the displacement controlled repeated load experiments,the energy absorption performance of the structure under trapping energy mode and repeatable energy absorption mode was studied.Using the method of natural aging,the effect of residual stress on the energy absorption performance of the structure was studied.At the same time,through the repeated tensile tests on the standard specimens and using the microscope to observe the microscopic morphology,the mechanism of the abnormal increase of the bearing capability of the structure was revealed.Based on this,a kind of strengthening method was proposed,which can greatly increase the bearing capacity of the structure by adjusting the morphology of the microstructure through displacement loading.