Numerical simulation of the integral hydro-bulge forming of non-clearance double-layer spherical vessels: deformation analysis

The integral hydro-bulge forming (IHBF) process of non-clearance double-layer spherical Vessels is analyzed by means of the explicit finite element code LS-DYNA3D. The deformation process of the double-layer shell from the initially flat-blank frustum shell to the final spherical shape is discussed, the final diameter and its variations, the development of the contact situation and the thickness distribution are fully analyzed. The numerical results agree well with the experimental results. During hydro-bulging, the inner shell is firstly deformed and then the outer shell begins deformation under the contact pressure from the inner shell, the two layer shells contact gradually each other, at the end of the process the two layers completely contact and are deformed into spherical shapes. The thinning is higher near every blank centre, lower at every blank edge and blank corner. The corners can be deformed into spherical shapes with appropriate deformation. (C) 1998 Elsevier Science Ltd. All rights reserved.