Abstract: The dieless hydroforming of spherical vessels from combination frustum shells is put forward in the present paper,and the forming process is developed by means of elastoplastic finite element method and experiments.In this paper the principle and experimental procedure of the new technology are introduced,the simulation method and the calculating assumptions are presented,the deformation process and the deformation characteristics of the shells are discussed,as well as the stress and strain distributions of the shell during bulging are analysed.

Key words: spherical vessel, FEM, hydrobulging, numerical simulation