Research On Cross-sectional Distortion And Springback Phenomenon Of Multi-point Stretch Bending Based On Internal Filling Support

For products manufactured in small batches,multi-point stretch bending is characterized by agile manufacturing,which can manufacture products with different curvatures at a lower cost in a short R&D time.However,when the hollow rectangular profile is formed by multi-point stretch bending,the shape structure of the cross-sectional has weak resistance to deformation,so it is easy to produce serious cross-sectional distortion,resulting in the profile unqualified.As we all know,springback is inevitable,so in order to form a profile with qualified shape,we must take certain measures to make the springback shape match the target curvature as much as possible.The finite element model was built based on the basic principle of multi-point stretch bending process with internal filling support,and the simulation results are reliable by reasonably dividing the mesh,setting constraints and loads.Through the simulation results,certain measures can be taken to reduce the cross-sectional distortion and springback error,which is essential for actual production.The detail content are as follows:(1)The principle of multi-point stretch bending forming based on the internal filling support was studied and analyzed.In multi-point stretch bending,the profile was reasonably meshed,the contact properties and boundary conditions were reasonably set by using the finite element analysis platform ABAQUS,so that the simulation results were reliable.(2)Based on the multi-point stretch bending forming principle with internal filling support,this paper studies the effects of pre-stretching,post-stretching and the shape of internal filler on the cross-sectional distortion during the forming process by analyzing the stress-strain distribution inside the hollow rectangular profile.By establishing the bending limit diagram of profile: the upper area of the bending limit curve is the safe forming area,and the lower area is the cross-sectional distortion area.The forming process can be reasonably planned,and the qualified parts are always formed within the allowable range of errors.(3)In this paper,a springback analytical prediction model related to the internal stress-strain of the profile is proposed.The stress-strain of the profile can be measured by finite element numerical simulation or strain gauge bridging experiment,so that the springback error of the profile can be predicted by using the springback model.The theoretical calculation,numerical simulation and experimental results are compared to verify the accuracy of the multi-point springback analytical model.(4)The biggest advantage of the multi-point stretch bending is that the mold surface can be adjusted,so the displacement reverse compensation method is used to reduce the springback of the profiles.The efficiency of springback compensation is mainly determined by springback compensation factor.In this paper,the secant method is used to calculate the springback compensation factor,which greatly improves the springback compensation efficiency,so that the springback error of the profile is small under the limited numbers of springback iteration compensation.