Analytical Modelling of Electromagnetic Bulging of Thin Metallic Tubes

Abstract

The main objective of this paper is to develop an analytical method based on the energy balance equation to model the plastic deformation of thin metallic tubes in a high velocity forming process under axisymmetric conditions. A yield criterion is proposed, which involves the coupled effect of the axial and circumferential internal force resultants. Using a combination of power-law strain hardening and strain rate hardening flow stress models, both strain hardening and strain rate effects are included. The proposed method permits consideration of the influence of different terms of kinetic energy and plastic work of the tube. The study presents a typical electromagnetic tube expansion model, using a dynamic high strain-rate forming method with strain-rates above 103 s−1. In this process, the deformation of the workpiece is achieved by the interaction of a current generated in the workpiece with a magnetic field generated by a coil adjacent to the workpiece. The results reveal that the achieved high strain rates influence the plastic flow stress and the final permanent radial deformation, consequently. The study concluded that an appropriate shape function eventuates a more accurate estimation of both the radial displacement and the deformed meridian profile.