Design And Mechanical Properties Study Of Zero Poisson’ Ratio Plate And Shell Cell Based On SLM

Zero Poisson’s ratio(ZPR)structures exhibit almost no macroscopic deformation in the normal direction of the load when subjected to compression,and they have great application potential in biomedical field,aerospace field,automobile manufacturing field and so on.Nevertheless,most of the existing zero Poisson’s ratio structures have evolved from positive and negative Poisson’s ratio structures;the internal components of the structure are mainly circular and rectangular cross-section rods,and stress concentration is prone to occur at the connection nodes of the cell elements.In addition,the research on the mechanical properties of zero Poisson’s ratio structures mostly focuses on two-dimensional small strain cases.In order to solve the above problems,this paper designs a three-dimensional zero Poisson’s ratio mechanical metamaterial cell,and uses selective laser melting(SLM)technology to rapidly form zero Poisson’s ratio mechanical metamaterials.In addition,experiments are conducted to analyze the zero Poisson’s ratio characteristics over a large strain range,and numerical simulation methods are used to study the loaded deformation modes of threedimensional zero Poisson’s ratio mechanical metamaterial cells.Through the above works,problems such as stress concentration in traditional zero Poisson’s ratio structures,fewer dimensions of zero Poisson’s ratio,and narrow strain ranges caused by zero Poisson’s ratio effects can be solved.In order to achieve the above objectives,the main work arrangements of this article are as follows:1.In order to avoid stress concentration in traditional zero Poisson’s ratio cells,plate shaped components are used to design zero Poisson’s ratio cells;In order to achieve threedimensional zero Poisson’s ratio characteristics,zero Poisson’s ratio cells are designed based on cubic symmetric cells.By adjusting the deformation geometric parameters: plate thickness d and angle θ,structural models with different parameters were obtained.In addition,a new type of plate shell cell structure with zero Poisson’s ratio was obtained by optimizing the cell structure combined with SLM forming conditions.Finally,SLM technology is used to form zero Poisson’s ratio structures with various parameters,which is convenient for experimental verification.2.In order to obtain a zero Poisson’s ratio structural cell with better mechanical properties,the SLM forming process parameters(laser power,scanning speed,and scanning spacing)were optimized through orthogonal experiments with the density of the cube sample as the optimization objective;and obtaining the mechanical properties parameters of SLM forming 316 L under this parameter group,providing a basis for subsequent numerical simulation.3.The variation of Poisson’s ratio of the designed mechanical metamaterial cell with structural geometric parameters was studied through quasi static compression experiments;the variation of Poisson’s ratio within different strain values was analyzed;and by testing different plate thicknesses and the inclination angle of the inner plate of the cell,the effects of structural parameters on the Poisson’s ratio characteristics and mechanical strength of mechanical metamaterials were analyzed,and better structural parameters were obtained.4.In order to deeply study the relationship between structural parameters-zero Poisson’s ratio-mechanical properties-deformation modes,an elastoplastic finite element model was constructed to study the elastic deformation stage,yield stage,and densification stage under different structural parameters.In order to deeply analyze the relationship between deformation and failure behavior and mechanical response,to study the global and local deformation modes and failure modes under different geometric parameters,and to reveal the mechanism of zero Poisson’s ratio generation.5.Finally,the zero Poisson’s ratio plate shell cell structure is applied to the optimization of an engineering example.Taking the car crash beam and battery box as examples,the optimization model is obtained after filling the cell structure.Through comparison of numerical simulation results,it is found that the optimized model has better played the advantage of zero Poisson’s ratio characteristics,and plays a protective role in the surrounding structure during extrusion deformation.In addition,the anti-collision beam mass is reduced by 44.3%,and the battery box mass is reduced by 59.2%,which can achieve the design goals of lightweight and protection.