Optimization Design And Research On Impact Resistance Of Structure With Negative Poisson’s Ratio Of Functional Gradient

The negative Poisson’s ratio lattice structure has higher shear modulus,fracture toughness,indentation resistance and impact resistance,which makes it have a wide application prospect in aerospace,vehicles,airdrop packaging and other anti-collision structures.In particular,the expansion effect of negative Poisson’s ratio structure makes its ability to absorb energy significantly improved,which has great research value for the research of lightweight protective materials.Therefore,it is of great significance to study the dynamic energy absorption properties of negative Poisson’s ratio grid materials.In order to establish the relationship between mechanical properties and geometric parameters of arrow type negative Poisson’s ratio lattice structure,and use it to deduce the relationship between energy absorption performance and geometric parameters.This paper first establishes two-dimensional and three-dimensional geometric models of structure by using Solid Works software.Based on the related knowledge of theoretical mechanics and material mechanics,the relationships among relative density,equivalent elastic modulus,equivalent Poisson’s ratio,equivalent plastic collapse stress and geometric parameters are derived.The accuracy of the theoretical relationship is verified by the comparison of quasi-static compression simulation with ANSYS software.In order to establish the relationship between energy absorption performance and geometric parameters of arrow type negative Poisson’s ratio lattice structure,and use it to provide guidance for the subsequent optimization design of geometric parameters.This paper fist establishes the simulation model under impact load,and observes the deformation mode.Then combined with the existing theory of calculating platform stress,the relationship between platform stress,platform enhanced stress,platform enhanced strain,densification strain and geometric parameters is derived.On this basis,this paper obtains the equivalent stress-strain curve,and then the energy absorption performance curve is obtained by integration.In order to optimize the design of arrow type negative Poisson’s ratio lattice structure with the aim of maximum specific energy absorption and minimum peak stress.This paper first establishes the optimization model.Because of the contradiction between the optimization objectives and the complexity of the optimization model itself,nine groups of sampling points are determined by optimizing Latin square design in the design domain of optimization model.This paper fitters an approximate second-order response surface model by the simulation results of sampling points,and a series of Pareto non inferior solutions are obtained by using non dominated sorting genetic algorithm NSGAII,then the comprehensive optimization solution is selected by satisfaction function.Finally,the energy absorption performance of positive gradient,negative gradient and uniform structure under different strain conditions are compared by means of theory and simulation.