Study On Elastic-plastic Constitutive Relationship Of Regular Hexagonal Honeycomb Structure

The honeycomb structure has many excellent mechanical properties such as light weight,high specific strength,high specific rigidity,good thermal insulation and sound insulation effect,strong energy absorption,diverse shapes and strong designability,and even can be designed by different configurations.To meet such special needs as zero Poisson's ratio or negative Poisson's ratio honeycomb structure.These characteristics make the honeycomb structure widely used in many fields such as aerospace,transportation,machinery,packaging,medicine and so on.Among them,the regular hexagonal honeycomb structure is the most common and commonly used honeycomb configuration,and people have studied it the most in-depth.However,when the external load is large,the research on the deformation and stress of plastic hexagons in the plastic deformation stage of the regular hexagonal honeycomb structure is still rare.Calculating the size of plastic hinges and studying the mechanical properties and constitutive relations of honeycomb structures with plastic hinges are of great significance for practical application.In this paper,the regular hexagonal honeycomb structure is taken as the research object,and single honeycomb cells are extracted.Based on the Euler-Bernoulli beam theory and the beam's large-deflection deformation bending theory,the honeycomb cell structure and load symmetry are simplified Stress deformation of honeycomb cells,and separate the cells into inclined wall plates and straight wall plates to study separately,thus establishing the elastic theory model and plastic theory model of the regular hexagonal honeycomb structure.The calculation formula of the plastic hinge and the nonlinear constitutive relationship of the honeycomb structure are derived.The elastoplastic theoretical analysis model established in this paper is based on solving a series of differential equations,and theoretically has higher accuracy than the finite element method.Then,the difference between the nonlinear constitutive relations of the honeycomb structure without considering plastic deformation and considering plastic deformation is analyzed,which shows that the plastic model is more "soft" than the elastic model.In addition,it is also found that the honeycomb structure in the stage of plastic deformation will produce a phenomenon that the rigidity decreases first and then increases due to the appearance of plastic hinges,and the conclusion that the tensile performance of such honeycomb structure is stronger than the compression performance The honeycomb structure has important reference significance.Then,in order to verify the accuracy of the theoretical model,the finite element software ANSYS was used for numerical simulation,a single regular hexagonal honeycomb cell model was established,and the nonlinear constitutive relationship of the model was obtained and compared with the theoretical results The error is about 7.9%,this error value can be accepted,which shows the accuracy of the ANSYS model.Finally,in order to study the factors that affect the nonlinear constitutive relationship of the regular hexagonal honeycomb structure,the effects of the material yield limit,the angle between the honeycomb cell sloping wall plate and the horizontal axis and the thickness-to-length ratio of the honeycomb wall plate on the nonlinear constitutive relationship of the honeycomb structure are analyzed.The results show that the yield limit of the material only changes the position of the plastic hinge,but does not change the shape of the constitutive curve;The angle between the honeycomb cell sloping wall and the horizontal axis has a great influence on the constitutive relationship of the honeycomb cell.It can be found that the smaller the angle,the longer the elastic deformation stage of the cell and the greater the elastic modulus,in other words,the greater the structural rigidity;From the results,the greater the thickness-to-length ratio of the honeycomb wall plate,the greater the Young's modulus of the honeycomb structure.This shows that the thicker the honeycomb siding,the less likely it is to deform.Based on the analysis results of these parameters,it can be concluded that the tensile performance of this type of honeycomb structure is better than the compression performance,and the vertical tensile and compression performance is better than the lateral tensile and compression performance.This conclusion can be used as a reference for the future production of this type of honeycomb structure.