Nosing of thin-walled PVC tubes into hollow spheres using a die

In a recent work, the authors presented a new single-stage nosing process for manufacturing metallic hollow spheres from thin-walled tubes that is capable of extending the formability limits of conventional nosing (Alves and Martins in J Strain Anal Eng Des 43:205-216, 2008). The fundamentals of the process were investigated by means of standard finite element analysis and its technological viability was evaluated by means of experimentation on industrial AA6060 aluminium alloy tubes. This paper is aimed on extending the scope of single-stage nosing so as to include the production of polymer hollow spheres. The investigation draws from the development of an innovative extension of the flow formulation that is capable of modeling cold plastic deformation of pressure-sensitive yield surfaces under a nonassociated flow rule to the identification and analysis of the major process parameters that influence formability and quality of the polymer hollow spheres. The overall performance of the process is assessed by means of a combined theoretical and experimental investigation made with industrial polyvinyl chloride (PVC) tubes. Results show that the innovative extension of the finite element flow formulation is capable of successfully modeling cold forming of polymers and that single-stage cold nosing of thin-walled PVC tubes can be successfully utilized for manufacturing sound hollow spheres.