| Electromagnetic forming technology uses the principle of electromagnetic induction to generate pulsed Lorentz force in metal workpieces to cause plastic deformation of metal materials,thus achieving the purpose of forming,which is one of the hot research topics in the field of forming technology in recent years.Its high-energy and high-speed technology is perfectly suited to the processing needs of lightweight alloys,and it is one of the important methods to achieve the goal of lightweighting and thus the goal of "double carbon".Traditional electromagnetic forming technology is usually single coil unidirectional electromagnetic forming,forming a single force field,the flexibility is poor.In response to this problem,some scholars have proposed multi-temporal electromagnetic forming as a green and flexible advanced manufacturing technology,using multi-coil multi-directional electromagnetic force to achieve more flexible forming,which is of great significance to achieve the manufacturing capability of lightweight alloy forming.Multi-temporal electromagnetic forming technology perfectly embodies the characteristics of flexible electromagnetic force regulation.At present,multi-temporal electromagnetic forming technology mostly focuses on axial-radial multi-temporal,with the development of electromagnetic forming technology,the emergence of attractive electromagnetic forming provides more possibilities for multi-temporal.Therefore,this paper proposes the attractionrepulsion composite electromagnetic forming scheme under the combined coil,and analyzes the feasibility and reliability of the attraction-repulsion composite electromagnetic forming technology in detail with the attraction-repulsion step-by-step loading as the time dimension and the attraction-repulsion mixed loading as the space dimension.In the time dimension,this paper proposes the attraction-repulsion time multi-step electromagnetic forming scheme under the combined coil,and introduces the current loading sequence and force loading mode of the time multi-step electromagnetic forming scheme from the principle of electromagnetic forming.The first reversal of the Lorentz force causes the tube to be expanded by attractive forces,and the second reversal causes the tube to be expanded with inward repulsive forces in the most uneven region.This matches the design of the stepwise electromagnetic forming scheme,and the final time multi-step electromagnetic forming scheme greatly improves the flatness of the tube expansion.In the spatial dimension,this paper proposes a scheme of attraction-repulsion spatial multidirectional hybrid force electromagnetic forming under combined coils.The distribution of magnetic field and eddy current of this scheme is analyzed theoretically,and then the force loading method is analyzed,and the feasibility of this scheme is verified by finite element simulation.It is found that 1)the compensation coil can effectively improve the magnetic field environment and eddy current competition,thus improving the electromagnetic environment during workpiece forming.2)Comparing the forming effect of spatial multidirectional hybrid force electromagnetic forming scheme,dual coil attractive force forming and first attractive force and then repulsive force forming scheme,it shows that the spatial multidirectional mixed force electromagnetic forming scheme is not a simple superposition of attraction and repulsive force.3)The forming effect of spatial multi-directional hybrid force electromagnetic forming scheme is closely related to the number of turns of the compensation coil,and the forming effect of the plate is poor when the number of turns of the coil is small.When the number of turns of coils is small,the forming effect is poor and it leads to competition failure.As the number of coil turns increases,the competing failure area disappears and the displacement will further increase.Further research shows that although the combined coil electromagnetic forming technology is effective,the coils are subjected to complex forces.Therefore,this paper investigates the reliability of the attraction-repulsion composite electromagnetic forming technology and conducts force analysis on the typical combined coils for electromagnetic forming under composite working conditions.It is found that in the horizontal coaxially distributed combined coil,the radial force of the inner coil is reversed during operation,so the force state of the inner coil skeleton should be paid attention to when designing the inner coil;the radial force of the outer coil is further increased after the inner coil is energized,so the force state of the outer coil reinforcement layer should be paid attention to when designing the outer coil.Vertical coaxial distribution of the combined coil induction eddy current coil great axial electromagnetic force combined force can make the coil skeleton lower end plate rupture,so in the axial direction should focus on the analysis of the coil skeleton lower end plate stress;coil radial Lorentz force due to changes in the electromagnetic environment shift,and when the discharge energy increases the coil great radial combined force can make the glass fiber fracture lead to coil explosion,so in the radial direction should focus on the analysis of The stresses on the glass fibers should be analyzed in the radial direction.And an optimization scheme for two typical combinations of coil forces is proposed. |
