Research On Springback Prediction And Springback Characteristics Of Thin-walled Profile Components In Three-dimensional Stretch-bending Process

In recent years,with the rapid development of the transportation industry,the aluminum alloy materials applied to the structural parts of the vehicle body have been widely used.The aluminum alloy materials can effectively meet the strength requirements while ensuring the weight of the vehicle body.The multi-point three-dimensional stretch forming technology is a new forming process for processing aluminum alloy materials,which not only has the technical advantages of adjustable die surface,but also can realize precise forming in three-dimensional space.However,since spingback is an inevitable phenomenon in the process of metal plastic deformation,and is affected by various factors such as material parameters,geometric parameters and process parameters,it becomes one of the main problems affecting the accuracy of three-dimensional bending and forming.For this reason,the thin-walled profile members are taken as the research object.The numerical simulation and experimental methods are used to predict the springback in the three-dimensional bending and forming,and the springback characteristics that affect the springback deformation are quantitatively analyzed.The main research contents and conclusions of this paper are as follows:(1)The three deformation stages in the bending and forming process are analyzed.The finite element model of the three-dimensional bending and forming process of the rectangular profile is established,and the finite element construction such as numerical simulation algorithm selection,mesh division and boundary condition setting are introduced respectively.The key problems in the mold process are processed.the stress and strain results of the three-dimensional stretch forming process are obtained.The geometry of the formed parts is smooth and the changes in stress and strain are continuous,and the simulation results are ideal.(2)Decomposing the 3D springback deformation into the horizontal and vertical springback,and establishing the springback evaluation system;using the ABAQUS predefined field function,based on the simulation results of the forming process,the springback prediction model is established and the spingback is obtained.The results of the prediction;based on the flexible multi-point three-dimensional bending and forming equipment developed by the research group,the effectiveness of the springback prediction model is verified by experimental methods.The horizontal and vertical maximum absolute errors of the springback prediction are 0.52 mm and 0.36 mm.The relative error is less than 15%.(3)Based on the numerical simulation model established above,the influence law of the process parameters on the springback characteristics is studied.The results show that the springback decreases with the increase of the elastic modulus of the material;the pre-stretching amount is back to the vertical direction.The amount of the elastic force is significant,and decreases with the increase of the pre-stretching amount.When the pre-stretching ratio is 0,the amount of spingback in the vertical direction decreases with the increase of the amount of the complementary stretching,but does not follow the pull-up.The amount of stretch is further increased and continues to decrease;when the pre-stretching ratio is 100% yield point,the amount of spingback in the horizontal direction decreases as the amount of stretch is increased.in addition,the number of multi-point molds is appropriately increased.It helps to reduce the rebound of the formed part,appropriately reduces the width of the multi-point die,and has an inhibitory effect on the spingback.The reduction of the friction coefficient between the formed part and the mold can improve the forming precision.(4)Based on the model,the influence of the geometric parameters of the workpiece on the springback characteristics is also studied.The results are as follows: in terms of bending radius,the horizontal springback increases with the decrease of the horizontal bending radius.The amount of springback in the vertical direction decreases.During the process of decreasing the radius of curvature in the vertical direction,the spingback amount in the horizontal direction decreases,and the spingback amount in the vertical direction increases.In terms of sectional shape,the shape of the section is affected.The effect is that the rectangular and L-section profiles have similar springback trends,while the springback deformation of the T-profile is similar to the L-profile in the horizontal direction,similar to the rectangular profile in the vertical direction;vertical with the increase in the section thickness of the profile The amount of spingback in the direction is significantly reduced.The cross-sectional size has little effect on the amount of springback in the horizontal and vertical directions.In this paper,the research on various process parameters and geometric parameters affecting the springback in three-dimensional stretch forming provides a reference for improving the forming precision in subsequent processing.