Elasto-viscoplastic FEM simulations of the aluminium flow in the bearing area for extrusion of thin-walled sections

The use of the finite element method (FEM) is getting increasingly important in the understanding of processes that occur during aluminium extrusion. The bearing area is one of the most difficult areas to model in a numerical simulation. To investigate the phenomena that occur in the bearing, detailed 2D simulations of the aluminium flow in this area are presented in this paper. In the simulations the effects of material behaviour, friction coefficient, bearing length and bearing angle art: investigated. It is demonstrated that elastic effects play an important role when the aluminium flows through the bearing channel. To accurately model this effect an elasto-viscoplastic constitutive model is necessary. It is observed that the resistance in a parallel bearing can be very sensitive to small changes in bearing geometry. This can explain the unpredictable behaviour of extrusion dies observed in practise. A design approach is suggested that reduces the sensitivity of the bearing. (C) 2001 Elsevier Science B.V. All rights reserved.