Basic Research On Electromagnetic Forming Process Of Point-by-point Continuous Flexible Sheet

With the pursuit of lightweight development in the fields of machinery,aerospace and automobile industry,lightweight aluminum alloy materials have been widely used.Using traditional methods to process aluminum alloy materials is prone to cracks,springback,wrinkling and other defects,which will reduce the performance and dimensional accuracy of the workpiece.Electromagnetic forming process is a high-speed forming process,which uses the instantaneous pulse magnetic field to form the metal workpiece.It has the characteristics of high forming speed,high efficiency and high surface quality.When applied to the forming of light alloy materials such as aluminum alloy,the plastic formability of materials can be improved and high-quality formed workpieces can be obtained.In this thesis,a point by point continuous flexible sheet metal electromagnetic forming process is proposed.The finite element model of electromagnetic forming with mutual coupling of electromagnetic field and structural field is constructed in ANSYS platform.The simulation calculation of sheet metal single point and point by point electromagnetic forming is carried out by using the sequential coupling method.Based on the simulation results,an experimental device for sheet metal electromagnetic forming is designed and manufactured.AA3003 aluminum alloy is selected as the experimental material for sheet metal electromagnetic forming experiment.The point-to-point continuous electromagnetic forming process of sheet metal is studied by the combination of numerical simulation and experimental research.Firstly,a two-dimensional finite element model of sheet metal single point electromagnetic forming in small area is constructed,and the influence of field shaper structural parameters on sheet metal forming factors is analyzed.The results show that the electromagnetic force on the sheet increases with the decrease of the thickness of the field shaper,the increase of the radius of the lower surface and the decrease of the ring width;The best field shaper parameters are thickness 4mm,inner radius 5mm,ring width 3mm,the maximum induced current density and node electromagnetic force peak on the sheet,faster deformation speed and high degree of fit;The field shaper effectively reduces the force on the formed coil.Then,the variation laws of magnetic line of force and electromagnetic force distribution,sheet metal structure deformation,forming speed,stress and strain in the process of sheet metal small area single point forming are analyzed and obtained.Due to the convergence effect of the field shaper on the induced current,the electromagnetic force of the sheet metal is mainly concentrated within 15 mm of the central area.The final forming effect of the sheet metal is good,and the stress on the central part is the largest.The bending deformation is completed first,and then the outer end of the sheet metal moves down and contacts the plane part of the punch.The stress zone and deformation velocity of sheet metal are mainly concentrated in the central region,which moves outward with the deformation time.The central deformation region is mainly affected by tangential and radial tensile strain and axial compressive strain.Then,the three-dimensional finite element simulation of sheet metal point by point forming is carried out,the structural deformation law of sheet metal is analyzed,and the interaction law of adjacent forming areas of sheet metal is obtained.The simulation results show that the electromagnetic force on the sheet metal is affected by the field shaper and distributed in an incomplete ring shape.The main deformation area is within 15 mm of the sheet metal center.The deformation shape of the second point forming area is affected by the deformed area.The deformation shape is different and overlaps with the deformation of the first point forming area to form a larger pit.Finally,through the electromagnetic forming experiment,the different forming effects of sheet metal under different discharge voltage,sheet metal and field shaper spacing are explored,and the best forming process parameters are summarized.The experimental results show that the forming height of sheet metal single point area increases with the increase of discharge voltage and the decrease of the distance between sheet metal and field shaper.Comparing the experimental results of sheet metal single point electromagnetic forming with the simulation results,it is found that the shape of the deformation contour curve of the two is consistent,and the relative error is less than 10%.The stress change curve of the experimental and simulation results is also similar,which verifies the finite element simulation results.The results of continuous forming of sheet metal point by point show that with the decrease of the distance between forming points,the overlapping part of adjacent forming areas becomes larger,and the final forming shape of sheet metal is more flat,forming a long strip-shaped pit.