Journal of Materials Processing Technology 166 (2005) 150–161 Investigation into hydrodynamic deep drawing assisted by radial pressure Part II. Numerical analysis of the drawing mechanism and the process parameters Lihui Lang ∗ , Joachim Danckert, Karl Brian Nielsen Department of Production, Aalborg University, DK-9220 Aalborg, Denmark Received 29 January 2003; received in revised form 4 August 2004; accepted 4 August 2004 Abstract A new method, named hydrodynamic deep drawing assisted by radial pressure, is proposed. Different from the conventional hydrodynamic deep drawing process (HDD), a radial pressure is loaded along the blank rim to reduce the drawing force. To explore the internal deformation mechanism, the numerical simulation was used for analyzing the forming process of an Al–Mg–Si aluminum alloy by using explicit dynamic finite element calculations utilizing non-quadratic yield criteria. Firstly, the loading boundary conditions were studied for the purpose of calculating the forming process accurately. The effects of sheet anisotropy on the material flow velocity distribution, the stress distribution, the strain distribution and the sheet thickness distribution were investigated. The optimum parameters were studied so that the flange wrinkling and fracture can be predicted and controlled effectively. The simulated results were in good agreement with the experiment. © 2004 Elsevier B.V. All rights reserved. Keywords: Hydroforming; Hydrodynamic deep drawing assisted by radial pressure; Aluminum alloy; Finite element simulation 1. Introduction The process of hydrodynamic deep drawing (HDD) as- sisted by radial pressure is shown in Fig. 1. This process is almost the same as the conventional hydrodynamic deep drawing [1–3]. In the HDD process assisted by radial pres- sure, when the punch goes down into the die cavity, the blank is forced into the die cavity filled with oil or the other liquids. The liquid in the die cavity will be pressurized and will push the blank tightly onto the punch surface. In the meantime, the liquid in the die cavity may flee out from the gap between the blank and the die. At the same time, because the gap g where the liquid flees out is very small, a liquid pressure exists around the blank rim. This is different from the conventional HDD process. The radial pressure can decrease the drawing ∗ Corresponding author. Tel.: +45 96357111; fax: +45 98153030. E-mail address: lang@iprod.auc.dk (L. Lang). force and the drawing ratio can be increased. Like the con- ventional HDD process, this process can also make a very high drawing ratio possible compared with the conventional deep drawing (CDD). Also, by using this process, many other advantages are obtained such as good surface quality, high dimensional accuracy and complicated formed parts, which can also be obtained with the conventional HDD process. Compared with other types of sheet hydroforming, the tools for this process are much simpler and no special sealing de- vices are needed [4,5]. This process is like the hydromechan- ical deep drawing without a draw die [6], however, there is a static lubrication in hydromechanical deep drawing without draw die which is different from a dynamic lubrication in HDD assisted by radial pressure. In recent years, the weight reduction of vehicles has been of great concern, consequently the production of high- strength aluminum alloys continue to increase. Particularly, the Al–Mg–Si aluminum alloy sheets are widely used in the 0924-0136/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2004.08.015