Study of preform and loading rate in the tube nosing process by spherical die

This paper develops an approximate theory, which combines the volume incompressible condition and Levy–Mises equation, to calculate preform shape, nosing ratio, and loading rate in the tube nosing process by spherical die. An elasto-plastic finite element method based on the updated Lagrangian formulation is used to verify the nosing ratio, tube end strain rate and thickness distribution at the preform site after nosing. From comparison of the results obtained in the theory and FEM, the relations of nosing ratio and tube end strain rate to punch stroke ratio, shows good agreement between the approximate theory and finite element prediction. A uniform thickness distribution, with small deviation form the expected thickness, was obtained for the preform site after nosing process. It proves that the analytical expressions will be able to provide a good reference guide for the tube preform design in the nosing forming.