Sectional Multi-point Forming Of Three-dimensional Surface Parts And Its Numerical Simulation

With the development of economy and technology,people are gradually pursuing diversification of products.Traditional mass and single production can no longer meet people's needs.As a flexible sheet metal forming method with the function of reconstructing die surface,multi-point forming can satisfy people's diversified and individualized production needs.Different from traditional dies,multi-point dies can realize a set of die devices to form a variety of workpieces,which greatly reduces the manufacturing cost of dies and shortens the manufacturing cycle of products.Therefore,the research of multi-point forming technology has important value.In this paper,sectional multi-point forming of three-dimensional surface parts is studied.The sectional multi-point forming technology is a flexible forming technology which combines the idea of sectional forming and the multi-point forming technology.The sectional multi-point forming technology makes full use of the discrete deformable forming characteristics of the multi-point forming equipment,and separately forms the large workpiece in different regions without division,the large workpiece is formed by small equipment.In this paper,multi-point die with fixed punch is applied to the multi-point forming of medium and heavy plate.By optimizing the factors affecting the forming quality,the forming parts with good forming quality are obtained.In addition,the application of multi-point forming with swing punch in thin sheet metal forming process is also studied.The application of swing punch can effectively restrain the defects of indentations,wrinkles and edge effect in sheet metal forming process.The main contents and conclusions of this paper are as follows:1.Numerical simulation study on influencing factors of sectional multi-point formingThe finite element model of sectional multi-point forming is established,and the material parameters,load and boundary conditions,contact and friction types,element types and meshing settings in the finite element model are discussed.The influence of overlapping region size,stamping direction and transition region design on forming results was studied.The results show that the reasonable design of overlapping region size can reduce the severe plastic deformation in sectional region,reduce the sectional indentation,and effectively improve the sectional forming efficiency of sheet metal.The design of stamping direction can make the overlapping region of the two forming processes coincide well,and the stamping stroke of the multi-point forming press can be minimized.This helps to keep the stress state in good condition,make the deformation uniform,reduce the non-uniform deformation of the transition region and improve the forming quality of the parts.The optimum design of the die in the overlapping region can make the buffer connection between the effective forming region and the rigid region,alleviate the severe plastic deformation in the transition region during the sectional forming process,and alleviate and eliminate the defects such as dimples,wrinkles and sectional indentations in the forming process.2.Experimental study on sectional multi-point forming processThe experimental scheme of sectional multi-point forming process for three-dimensional surface parts is conceived.The influence of the size of overlapping region,stamping direction and design of transition region on the results of multi-point forming is studied by sectional multi-point forming experiments.The results show that reasonable setting of overlapping region size,stamping direction and design of transition region can improve the efficiency of sheet metal sectional forming,reduce the stroke of press,alleviate the sectional indentation and non-uniform and severe plastic deformation of transition region during sectional forming,and restrain dimples,wrinkles and sectional indentations.3.Study on the influence of the ball radius of punch of multi-point die on the forming quality of sheet metalThe influence of ball radius of punch of multi-point die on sheet metal forming quality is analyzed.The results show that reasonable increase of ball radius of basic body can increase the contact area between forming surface and multi-point die,disperse the stress and strain between basic body and forming surface,weaken the local severe deformation of contact position,and improve the quality of forming parts.In order to avoid interference between multi-point die and sheet metal caused by too large ball radius,a multi-point forming device with swing punch was proposed.4.Numerical simulation of multi-point forming with swing punchDifferent from the multi-point die with fixed punch,the punch of multi-point die with swinging punch can swing freely.The envelope surface formed by the swinging punch can replace the traditional die surface for sheet metal forming.The forming quality of sectional multi-point forming with swing punch is simulated and analyzed by means of finite element numerical simulation,and compared with that of multi-point forming with fixed punch.The results show that the sectional multi-point forming with swing punch can effectively restrain the forming defects such as dimples,wrinkles and sectional indentations,and the experimental parts with good forming quality can be formed.5.Experimental study on sectional multi-point forming process with swing punchThe characteristics and advantages of multi-point die with swing punch and the forming principle and process were explored.According to the principle of single variable,the sheet metal forming experiments were carried out under the conditions of multi-point die with swing punch and multi-point die with fixed punch respectively.The results show that the punch of the multi-point die with swing punch can swing with the shape of sheet metal,increase the contact area between the multi-point die and the sheet metal and the normal constraint of the multi-point die on the sheet metal,effectively reduce and eliminate the forming defects such as dimples,wrinkles and sectional indentations in the forming process of the multi-point die with fixed punch,and the experimental parts with good forming quality can be obtained.