Equivalent Model And Structure Optimization Of Impact Protection Periodic Structure

With the progress of science,technology and society,superstructure has attracted the attention of researchers.The most common of these structures are negative Poisson’s ratio structures,which have light mass,crashworthiness,high shear stiffness,high strength,low density and the ability to absorb impact energy.In this paper,topology optimization was used as an optimization tool to construct a honeycomb structure with negative Poisson’s ratio effect,which had a good impact performance.The impact dynamics of this structure was studied and analyzed by finite element simulation.Then the thickness gradient was introduced and a new gradient optimization algorithm was proposed.Finally,the equivalent mass-damped-spring model of honeycomb structure was proposed and its application range was given.The main contents were as follows:Using returnable hexagonal honeycomb structure(RHH)as primitive cell,a new concave hexagonal honeycomb structure was constructed by topology optimization method.Compared with other common negative Poisson’s ratio honeycomb structures,this new concave hexagonal honeycomb structure had a more prominent energy absorption capacity.The stress formula of the plateau of this structure was deduced by the energy method and verified by finite element software(ABAQUS).The mechanical properties of the new concave hexagonal honeycomb structure were further investigated,among which there were three deformation modes: type I,type V and type XV.The negative Poisson’s ratio effect decreases with the increase of the impact velocity.The densification strain was related to the thickness of the structure and the impact velocity.In addition,the influence of the geometric parameters of the structure on its energy absorption was also studied.Selecting the appropriate geometric parameters can give full play to the energy absorption capacity of the structure.The influence of thickness gradient on the energy absorption of the structure was investigated.Different thickness gradient arrangement would have different influence on the structure energy absorption.In order to find the appropriate thickness gradient,ABAQUS software was integrated into Isight software for thickness gradient optimization,and a set of ideal thickness gradient values were found,which made the new honeycomb structure more prominent in energy absorption.In addition,in order to improve the efficiency of gradient optimization,a new gradient optimization algorithm was proposed and its formula was derived.By comparing two optimization algorithms,namely software integration method and formula optimization algorithm,it was found that formula optimization algorithm was more efficient.A mass-spring-damping model is established to describe the constant velocity impact behavior of honeycomb structures.The equivalent model of honeycomb structure was rare.In order to simplified the mechanical analysis of honeycomb structures(displacement and energy absorption),an equivalent model of mass-spring-damping system was proposed to describe the displacement and energy absorption of honeycomb.Taking hexagon honeycomb structure as an example,the equivalent theory was presented,and its correctness was proved by numerical simulation.Different honeycomb structures were also discussed and the applicable range of the theory was given.The new hexagonal honeycomb structure belongs to the applicable scope of the theory,so the theory is applied to the new hexagonal honeycomb structure,which can be described by the mass-spring-damping model.