Research On Sheet-bulk Metal Forming Of Imitating Honeycomb Thin-walled Structure

Bionic design has great potential for realizing the lightweight of automobiles,and the imitation honeycomb structure is more and more used in automobiles because of its excellent performance.However,there are shrinkage defects when using common casting technology to produce this kind of structural parts,and the material utilization rate is low when using cutting method.In order to solve the above problems,the sheet-bulk metal forming process is proposed to fabricate the honeycomb like thin-walled structure.At present,the process of metal flow in the die cavity,the distribution of stress and strain in the deformed body and the formation of defects in the sheet-bulk metal forming process of imitated honeycomb parts have not been explored.This paper mainly carried out the following research work:(1)Mechanical analysis of the sheet-bulk metal forming process of the honeycomb structure.The principal stress method is used to study the mechanics of the deformation body in the deep drawing stage and the upsetting stage.The main flow types of metal in upsetting stage are axisymmetric upsetting and plane strain extrusion.The formulas of compressive stress and unit deformation force of each basic plate are derived.On the other hand,through the numerical simulation of bionic structure,the stress and strain distribution of the deformed body in the upsetting stage,the punching force and the die stress at the end of forming are mainly discussed.(2)Defect analysis in the sheet-bulk metal forming process of the imitated honeycomb structure.Due to the crisscross ribs and the complicated metal flow,defects are easily generated during the forming process and the forming quality is affected.In this paper,the three-dimensional numerical simulation test of single cell structure is carried out.Combined with the metal flow process and stress analysis,the basic defects of inner rib folding,outer rib folding and outer rib under filling are revealed when the metal filling cavity is uneven in the upsetting stage.It is concluded that promoting the metal flow to the outer rib cavity can control the defects.At the same time,the height difference of outer rib and punch stroke at typical deformation time are proposed as quantitative evaluation indexes of defects,and the safety range of evaluation indexes without under fill and folding defects is discussed.(3)Optimal design of process parameters for the sheet-bulk metal forming of imitated honeycomb structure.Unreasonable process parameters can not only reduce the yield,but also increase the forming load.Therefore,the optimization work is carried out based on neural network algorithm and genetic algorithm.The high precision prediction model of forming load,height difference of outer reinforcement and stroke was established by using Latin hypercube experimental design method.Then,the forming load was taken as the optimization objective to solve the optimal combination of process parameters.Finally,the simulation results show that the error between the predicted value and the test value is small,and the forming load value and the die stress peak are significantly reduced.It is proved that the optimization design method adopted in this paper is efficient and the optimization results are reliable.The optimization method proposed in the thesis can be used to solve similar problems.The research results provide a new idea for the integral forming of bionic thin-walled structures.