Large ellipsoid parts manufacture using electromagnetic incremental forming with variable blankholder structure

Abstract

The large ellipsoid parts are the main load-bearing components in the rocket tank, which are prone to wrinkle when using the traditional stamping. In order to solve the wrinkling problem in large parts, the EMIF method with a variable blank holder is proposed in this paper. The numerical simulation has shown that the sheet material near the blank holder is, as a consequence of stamping, subjected to circumferential compressive stress. When the drawing height was 100 mm, the sheet metal was notably wrinkled. In the electromagnetic forming (EMF) process, the sheet region facing the coil becomes thinner.However, the sheet metal thickness corresponding to the coil edge increases with the increase in forming height. If the EMF forming height is 150 mm, the sheet, which is in contact with the smooth mold, is deformed without a wrinkle. Compared to the traditional stamping, the EMF can signi cantly reduce the sheet metal wrinkling, improving the deformation height of the sheet metal smooth area.