Research on hydro-forming of spherical shells with different preform types

Abstract

To avoid out of round during hydro-forming of the orange shell with small polar plates, a new preform shell with basketball type has been designed before hydro-forming. The theory for trending spherical shell from single-curvature preform shell was analyzed. The results demonstrated that the performance difference between original sheet and weld seam does affect the deformation behavior. The roundness was analyzed by numerical simulation for hydro-forming of the basketball and orange spherical shells; and the influence of preform type was discussed on out-of-roundness. It is shown that 0.65% out-of-roundness on the 90° cross section of orange preform shell still existed when the internal pressure made the basketball preform shell to a sound circle on each section. Furthermore, an experiment was conducted on hydro-forming of basketball and orange shells with diameter 160 mm. The deformation of the shell shapes, variations of the diameters, volume change, and thickness distributions were measured in the experiment. The basketball shell has more accurate shape and uniform thickness than orange shell under the same internal pressure. It is proven that hydro-forming of the basketball preform shell is reasonable and this new type is suitable for manufacturing of the spherical shell.