END FORMING OF THIN-WALLED TUBES USING A DIE Gouveia B. P. P., Alves M. L., Rosa P. A. R., Rodrigues J. M. C. e Martins P. A. F.
Resumo: The term 'end forming of tubes' usually refers to a wide variety of shapes and profiles such as expansions, reductions, inversions, flares, flanges and tapers that can be obtained by means of single or multiple metal forming processes.
Basic design rules for the end forming of thin-walled tubes using a die are mainly derived from the accumulated experience of both manufacturers of tubular parts and suppliers of machine-tools. Very few systematic studies have been done, as far as authors are aware, on the influence of process parameters on the formability limits induced by ductile fracture, wrinkling and local buckling. These topics are crucial for a wider comprehension of the mechanics of the process and for accomplishing an adequate characterization of the different modes of deformation (i.e. for successfully predicting the geometrical profiles found in daily practice).
The research work supporting this paper was based on a comprehensive numerical and experimental investigation on the expansion, reduction and nosing of thin-walled tubes using a die with the purpose of complementing some of the above mentioned gaps of knowledge.
The theoretical investigation was accomplished by the utilisation of virtual prototyping modelling techniques based on the finite element method and combines axisymmetric and three-dimensional simulations in order to successfully model the full geometrical details of the tube and tooling and to take into account the non-symmetric characteristics of certain modes of deformation that are induced by wrinkling, buckling and fracture. The experimental work on industrial Al6060 Aluminium alloy tubes under laboratory-controlled conditions was mainly utilized for supporting and validating the theoretical investigation.
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