Title: Evaluation of the effects of a movable tool in the hydroforming process

Authors: Gianfranco Palumbo, Luigi Tricarico, Shi-Hong Zhang, L.X. Zhou, Joachim Danckert, Karl Brian Nielsen

Addresses: Department of Mechanical and Management Engineering, Politecnico di Bari, Bari, Italy. ' Department of Mechanical and Management Engineering, Politecnico di Bari, Bari, Italy. ' Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China. ' Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China. ' Department of Production, Aalborg University, Fibigerstraede 16, DK-9220 Aalborg, Denmark. ' Department of Production, Aalborg University, Fibigerstraede 16, DK-9220 Aalborg, Denmark

Abstract: In this paper, the production of stainless steel hemi-toroidal parts has been investigated using three different processes: the conventional stamping, the standard sheet hydroforming and the hydroforming adopting a movable die (MD) which can have a vertical stroke and whose shape completes the female die cavity. Tests adopting the MD were performed at Aalborg University using a specific experimental equipment; numerical simulations were performed using ABAQUS\Explicit and were aimed at investigating the effect of the friction condition of the MD tool on the blank deformation. The friction coefficient was varied on both the whole surface of the MD tool and locally (in the region of the MD corner radius). The role of the MD in the hydroforming process was thus studied by comparing results in terms of thickness and strain distributions on the final part obtained adopting the same geometry of tools, but different forming techniques. Simulations put in evidence that a moderate increase of the friction can be successfully used for reducing thinning if the MD is adopted; in addition, the friction in the region of the MD corner radius shows to play a key role in forming sound parts.

Keywords: sheet hydroforming; movable tools; hemi-toroidal shapes; finite element method; FEM; stainless steel parts; stamping; movable dies; friction coefficient; blank deformation; thickness; strain distribution; forming techniques; simulation.

DOI: 10.1504/IJMPT.2010.033818

International Journal of Materials and Product Technology, 2010 Vol.38 No.4, pp.386 - 398

Received: 27 May 2008
Accepted: 13 May 2009
Published online: 02 Jul 2010 *

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