Springback Analysis And Control For Stainless Steel Butterfly Diaphragm In Stamping Process

The diaphragm-shaped workpiece has the advantages of compact structure,low cons?med material and light weight and so on,and it is widely used in aerospace,automobile,petrochemical,electrical equipment and shipping industry.With the rapid development of these industries,the demand of diaphragm-shaped workpiece also acquisiton sustainable growth.The kinds of materials and structure of diaphragm-shaped workpiece exhibit a diversity step by step.The traditional processing methods such as rolling forming and turning are limited by the small stiffness of diaphragm-shaped workpiece,and they also have a relative lower production efficiency witch can not meet the industry demand.Stamping forming can solve the low stiffness weakness of diaphragm-shaped workpiece and it also have the advantage of high production efficiency.But this kind of workpiece also have a relative big springback amount after stamping forming because of its geometric dimension and material property.Springback is a confusing phenomenon for many thin-wall workpiece.Predecessors have do a lot research on mold technological parameter optimization and profile surface compensation,much research achievement have gained for these years,but they mainly focus on U-shaped workpiece and V-shaped workpiece,there is a little study for diaphragm-shaped workpiece,especially for diaphragm-shaped thin-wall workpiece.This paper focus on the springback analyze and control,all research are based on 304 stainless steel.Firsty the springback analyze for different kind of diaphragm-shaped thin-wall workpieces are done by the proving and validated finite element model.And the auxiliary structure with internal boss and external brake bead are raised.The effectiveness of this kind of auxiliary structure are certified under the condition of different case by finite element model and one case by experiment.The springback percentage influence of structure parameters for boss are analyzed by single factor method,and combine with response surface method,the structure parameters processing window is determined for a certain workpiece,which help to the design and manufacture of the forming mold.The research contents and results can be concluded as bellow:1)Build the stamping experiments platform and finite element model for the diaphragm-shaped thin-wall workpiece;The stamping mold are designed and manufactured.Based on 304 stainless steel,the basic material parameters such as elasticity modulus are obtained though uniaxial tensile tests and microhardness test,also the fitting relation between Vickers hardness and ture stress is obtained.The stamping and springback finite element model for diaphragm-shaped thin-wall workpiece is set up,and it is certified by forming height and stress distribution condition in the macro and micro respectively,which help to lay a solid foundation for the further springback study of diaphragm-shaped thin-wall workpiece.2)Analyze the spingback phenomenon and put forward the control method for diaphragm-shaped thin-wall workpiece;Based on the certified finite element model,further springback study for diaphragm-shaped thin-wall workpiece is developed.The influence of inner radius,forming angle,forming height,fillet radius and plate thickness for springback percentage are discussed and their effects are concluded to the influence on the corner stress condition of the diaphragm-shaped thin-wall workpiece.Results showed that inner radius,forming angle,fillet radius and plate thickness have relative important influence on springback percentage but forming height,and diaphragm-shaped thin-wall workpiece witch has bigger inner radius,bigger forming angle,binger fillet radius and thinner plate thickness may have relative striking springback percentage.3)Investigate the influence of boss structure and determine the structure parameter processing window;The auxiliary structure of internal boss and external brake bead to change the corner stress condition of diaphragm-shaped thin-wall workpiece is proposed,which can help to increase the plastic strain and enlarge the material range at corner for plastic strain.Base on the finite element model the results showed that this structure has effective influence on springback for different kinds of diaphragm-shaped thin-wall workpiece,which has been proved by experiments.What's more,as for a certain case like bellows accumulator's key component,the single factor method and response surface method are used to determine the boss structure.The single factor method pointed out the boss draft angle,boss distance and boss forming height have relative important effects on springback percentage.Furthermore,based on three factor and three level Box-Behnken method the response surface analyze are carried out,and the boss structure windows is obtained to guide the design and manufacture of forming mold,the spingback percentage is control at about 5% finally which says this method has a effective control results and meets the processing demands.