Forming of thin-walled tubes into toroidal shells

The purpose of this paper is to introduce a new forming process that is capable of shaping thin-walled industrial tubes into toroidal shells in a single-stage operation. The methodology draws from the existing know-how on conventional end forming of tubes to aspects of deformation mechanics that are necessary to identify the typical modes of deformation and to establish the formability limits in terms of the major process variables. The approach is illustrated and enriched with selected test cases obtained from finite element modelling and experimentation and the overall presentation is expected to effectively contribute to transferable of original technological knowledge. The new proposed process is a fast and low-cost manufacturing alternative to existing solutions for producing toroidal shells that are based on incremental forming and hydroforming. However, it is shown that the overall feasibility of the process is limited to toroidal shells having slenderness ratios within a compact range in order to avoid superposition of material along the equatorial plane and to prevent fracture during forming.