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 importan t 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, detail ed 2D simulations of the aluminium flow in this area are presented in this paper. In the simulations the effects of material behaviour, friction coeff icient, bearing length and bearing angle art: investigated. It is demonstra ted that elastic effects play an important role when the aluminium flows th rough the bearing channel. To accurately model this effect an elasto-viscop lastic constitutive model is necessary. It is observed that the resistance in a parallel bearing can be very sensitive to small changes in bearing geo metry. This can explain the unpredictable behaviour of extrusion dies obser ved in practise. A design approach is suggested that reduces the sensitivit y of the bearing. (C) 2001 Elsevier Science B.V. All rights reserved.