Performance Analysis And Forming Technology Optimization Of Egg-Box Structure

Egg-box structure is a new type of lightweight plate with periodic characteristic.By stamping,the sheet metal can be changed to lightweight structure with low density,high specific strenth,high specific stiffness,and high energy absorption capacity.However,at present,there are few studies on the mechanical properties and the relationship between compression characteristics and structural parameters.Meanwhile,the traditional stamping method has limited the production and popularization and application of this kind of structure because of the limitation of the size and the low processing efficiency.To deal with these questions,this paper studies the performance of egg-box structure and the manufacturing process separately by using theory,experiment and finite element etc.This study provides a theoretical basis for the manufacture and application of the egg-box structure.The main contents and main conclusions of the paper are as follows:(1)The variational asymptotic method is used to establish the numerical calculation model of the equivalent stiffness characteristic of the egg-box structure.Due to the change of the topography,the equivalent rigidity characteristic is lower than that of the base plate,and the bending stiffness is more larger.The effect of structural parameters and material parameters on the equivalent stiffness characteristic is analyzed.The equivalent negative Poisson’s ratio of the egg-box structure under small strain is analyzed by using the calculated equivalent stiffness characteristic.The regression model of the equivalent Poisson’s ration is obtained.(2)The compression characteristics of the aluminum egg-box structure are analyzed by experiments and finite element methods analysis.The relationship between compression characteristics and the structural parameters is obtained.The effect of the thickness,periodic spacing,height of the egg box structure of the basic structure after forming on the compression characteristics is discussed.The quasi-static compression characteristics of a multi-layered egg box structure are experimentally analyzed.And the influence of the thickness distribution of the base plate on the compression failure of the double-layer egg box structure are analyzed.The failure modes of the compression process of different layer egg box structure and the unit mass energy absorbing capacity of different thickness structure are obtained.(3)The finite element method is used to analyze the influence of the punch radius and the process parameters on the forming result in the egg-box structure stamping process.The design method of the size of the punch is proposed,and stamping die is designed and machined according to this method.The structure of aluminum egg-box is obtained by this forming mould.Comparing the result of finite element calculation with the result of stamping,the correctness of the finite element model is validated.Using this model,the formability range and the maximum stamping force of the egg-box structure in a typical size range are obtained.(4)The roll forming method is applied to the forming process of the egg-box structure.By analyzing the relationship between the envelope and roll radius in roll forming process,the theoretical calculation formulas of rolling forming process and actual stamping process profile error are obtained,which provide a basis for the choice of roll radius.The mechanics parameter of the roll forming process is analyzed by finite element method.Comparing the shape error and the thickness distribution after forming,the roll forming result shows the directionality.Then the influence of roll radius and friction coefficient on the related mechanics parameters,morphology and thickness during roll forming process are analyzed,which provides some theoretical basis for the design of rolling forming die and process design of egg-box structure.(5)The advantages and disadvantages of egg-box structure are obtain by comparing with some other lightweight structure.By combining with the stiffness characteristics,compression characteristics and formability of the structure,the optimal design model of egg-box structure parameters is established.And the rolling forming die design method is proposed for specific structure.This study provides theoretical guidance for the future practical application and production of the egg-box structure.