External inversion of thin-walled tubes using a die: experimental and theoretical investigation

External inversion of thin-walled tubes using a die is used for producing double-walled parts that are difficult to manufacture by any other technique. Previously published works in the field generally provide the main geometrical and material parameters that govern the process. However, insufficient knowledge can still be found in understanding the influence of interface friction on the material flow and of the strain path and material damage on the occurrence of fracture. Moreover, although the analytical conditions for the occurrence of buckling are easily available in the literature its numerical modelization is usually not commonly available. This paper presents a comprehensive numerical and experimental modelling of the external inversion of thin-walled tubes with the purpose of reexamining the process mechanics and obtaining a better understanding of the deformation modes associated with its formability limits. Fundamental research is undertaken by using virtual prototyping modelling techniques based on the finite element method. The experimental work is performed on Aluminium Al6060 industrial tubes and it is mainly utilized for supporting and validating the theoretical investigation. (C) 2003 Elsevier Science Ltd. All rights reserved.