Research On Electromagnetic Blanking-flanging Compound Forming Of Aluminum Alloy Y-shaped Tube

For the high requirement of lightweight manufacturing and high reliability in aerospace field,based on the characteristics of the electromagnetic forming,an new electromagnetic blanking-flanging compound forming is proposed for aluminum alloy thin-walled Y-shaped tube forming.The lateral punching of tube is realized by electromagnetic force generated by a helix coil,and the flanging of Y-shaped oblique hole is completed by inertia force.Not only the forming process and die structure are simplified,the formability of the material is also improved by high strain rate.Taking6063 aluminum alloy pipe as the research object,the die design method and the blanking and flanging process of tube were systematically studied,and the effects of process parameters on forming quality were discussed.Firstly,based on the consistency assumption of circumferential forming height of branch and the flow characteristics of material in the process of lateral flanging of tube,the geometric design scheme of the oval section profile of blanking edge was established through mathematical derivation,and a complete set of compund forming tools was designed and manufactured.Secondly,the Johnson-Cook constitutive model and failure criterion of 6063-O aluminum alloy were established by reverse identification method and electromagnetic flanging experiment.The analysis model of blanking-flanging process was established by LS-DYNA,and the deformation behavior of the workpiece was simulated.The results show that: After the blanking process,the electromagnetic force rapidly attenuates,and the workpiece is mainly flanged by inertia force.Due to the uneven distribution of electromagnetic force and the asymmetry of material flow,the deformation of flanging branch is not uniform,and finally results in the uneven distribution of branch height,thickness and die-fitting gap along the circumferential direction.According to the strain analysis of deformation region,the rounded region is approximately plane strain,the edge of branch is single tension zone,and the middle region is double tension zone.The plane strain region and the double tension region are conducive to the increase of material flow and forming height,while in the single tension region,the circumferential strain is the largest,and the axial strain is negative,which is not conducive to flanging forming.Therefore,the single tension region should be suppressed while the other two regions should be expanded by regulating and controlling the distribution of electromagnetic force and the fillet of flanging die.In addition,the effectiveness of blanking edge profile design scheme is verified preliminarily by simulating the forming process.And the effect of edge angle on the subsequent flanging process.The results show that the suitable edge angle can restrain the uneven deformation of branch area and promote the flanging forming,If the edge angle is too large,the edge will be passivated and the inhomogeneity of deformation will be intensified,which is not conducive to the subsequent flanging forming.If the edge angle is too small,the mold will be easily worn and the durability will be reduced.Considering comprehensively,the blanking edge angle is designed as 40°.Finally,the 6063-O aluminum alloy tube with outer diameter of 50 mm and initial thickness of 1 mm,1.2 mm and 1.5 mm respectively were formed by a series of electromagnetic blanking-flanging compound forming,which verified the feasibility of the process scheme and the effectiveness of the mold design method.The die-fitting gap of formed branch is less than 0.2 mm,and the end height difference is less than 0.25 mm.The maximum thickness reduction rate is 35.33%.The distribution of flanging height,thickness and die-fitting gap were compared with the simulated results,and the relative error between the simulation values and the experimental values was small,which verified the accuracy of the analysis model.The experimental results show that when the initial thickness of tube is constant,the flanged height of branch increases with the increase of discharge voltage,the thickness reduction of branch edge increases,and the die-fitting gap decreases firstly and then increases.The discharge voltage has an optimal value,at which the flatness of the flanging branch end is the best and the precision of die-fitting is the highest.When the discharge voltage increases at the same rate,the smaller the initial tube thickness is,the larger the die-fitting gap,the higher the flanged height and the thinner the wall thickness are.When the ratio of the long axis of the blanking edge to the length of the coil is too large,it will aggravate the uneven distribution of electromagnetic force in the flanging area,and the flanged area at the long axis of the blanking edge is prone to fold.And when the discharge voltage is too high,the flanged area at the short axis of the blanking edge will rebound severely,and affects the sticking precision.