Analysis of Electromagnetic Force And Formability of Tube Electromagnetic Bulging Based On Convex Magnetic Field Shaper

In order to solve the problems of non-uniform axial deformation and thinning of wall thickness in traditional tube electromagnetic bulging, a method of tube electromagnetic bulging based on convex magnetic field shaper is proposed in this paper. The electromagnetic-structure coupling model is constructed by using COMSOL software, and the influence of convex magnetic field shaper structure on radial and axial electromagnetic force, axial deformation uniformity and wall thickness reduction is analyzed, and compared with traditional tube electromagnetic bulging. The results show that by using this method, the axial deformation uniformity is increased by 4.2 times, and the relative wall thickness is reduced by 33%. Obviously, this method of tube bulging can effectively overcome the problems existing in traditional tube electromagnetic bulging and promote the wide application of electromagnetic forming technology.

Investigation on wrinkling behaviors of metal thin-walled tube in pulsating hydroforming with axial feeding

Pulsating tube hydroforming with axial feeding is an effective method to improve the forming performance of thin-walled tube. A beneficial wrinkle can make the tube wall thickness more uniform and create a greater bulging height during forming process. The method of expressing the degree of wrinkle with geometrical and mechanical criteria is applied to distinguish the wrinkle types, and thus, the wrinkles can be divided into beneficial ones and harmful ones based on the deformation wrinkle features with different forming parameters. The wrinkling behavior in tube pulsating hydroforming with axial feeding was investigated in this article by experimental study, numerical simulation and theoretical analysis. The results showed that loading parameters had great influence on formability and wrinkling behaviors and that the beneficial wrinkles could be identified and used effectively by controlling the relation of wrinkling degree and forming parameters. Furthermore, the evolution processes of wrinkling behaviors in tube-bulging experiment were observed, the characteristics of wrinkling in every stage were analyzed and the relationship between wrinkling degree and forming parameters was established in the experiment.

Effect of Pre-Bending on Formability of DQ Steel and Al 5182

The effect of the pre-bending operation on ductility can be significant in determining the limit strains of the final product. The strain path experienced in straight tube bulging is significantly different from that of elbow (tube with pre-bending), leading to a reduction in bulge height. The Tube bending introduces strain gradient both along the tube and across the tube. In this work the effect of pre-bending on limit strains during tube bulging process is predicted — and the results are compared to the limit strains of bulged tubes without pre-bending. The Finite Element (FE) model of the bending operation is developed which utilizes an explicit dynamic finite element formulation. The PAMSTAMP 2G code is used to perform the numerical pre-bend (and bulging) simulations. Tension side of bend tube axial strain is found to be positive and hoop strain as negative and vice versa along the compression side. During the bulging, the neck usually develops perpendicular to major strain direction. During bend tube bulge test with fixed expansion and axial feed expansion of bend tubes, in both cases the crack is found to be in the axial direction.