Abstract
Controlling the direction and profile of the electromagnetic force (EMF) is a key of improving the tube axial-uniformity and wall thickness during the electromagnetic forming process. In this regard, this article proposes a new tube electromagnetic-bulging topology using internal negative-external positive three-coil system. This structure is aimed at realizing effective bidirectional loading of axial and radial EMFs on the tube. An electromagnetic-structure coupling two-dimensional model is proposed to study the effect of the coil structure on the EF profile, bulging profile and the tube wall-thickness. The performance of the proposed method is compared with the traditional method through several performance metrics that include the electromagnetic force distribution cloud map, the tube bulging uniformity and its wall thickness. Numerical simulation results show that by changing the coil structure, the radial EMF profile can be effectively enhanced, and the free bulging contour of the tube can be further regulated. The additional axial EMF due to the proposed structure can promote the axial-flow of the material, thereby suppressing the reduction in the tube wall-thickness which is unavoidable using the traditional method. In comparison to the traditional single-coil system bulging, the maximum axial uniformity range of the tube is increased from 6.5mm to 35.2mm, and the wall thickness of the most severely thinned area is increased from 1.43mm to 1.77mm which verifies the effectiveness of the proposed method.
Highlights
The use of lightweight alloy materials has been of a great significance to the rapid development of aerospace, transportation and large machinery [1,2,3,4,5]
As such traditional forming methods have been replaced by electromagnetic-based techniques that employ electromagnetic force (EMF) to accomplish the forming-process of alloy materials [7,8,9]
In order to improve the homogeneousness of the axialdeformation of formed tube, Mo Jianhua [20] incorporated the idea of progressive forming into the traditional electromagnetic bulging process
Summary
The use of lightweight alloy materials has been of a great significance to the rapid development of aerospace, transportation and large machinery [1,2,3,4,5]. [22] proposed a 3D numerical simulation model of a magnetic-structure field coupling to study the metal tube uniformity under electromagnetic bulging. When the plate is deeply formed, the material flow is reduced in the radial-direction which results in a severe reduction in the plate’s wall-thickness and makes it more prone to breakage. The above methods suggest that by changing the relative position of the driving coils and / or its structure, the uniformity of the workpiece can be effectively improved and the decrease in the workpiece wall-thickness can be suppressed. An effective topology to simultaneously solve the two issues of tube deformation uniformity and wall thickness reduction has not been given much attention. To simultaneously increase the forming homogeneousness of the tube and suppress the wall-thickness reduction, this article presents an electromagnetic-forming topology based on inner negative-outer positive three-coil system tube. Effectiveness of the proposed topology is examined using an electromagnetic structural finite element analysis for the tube wall displacement in electromagnetic bulging as elaborated below
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