Finite Element Modelling of Complex Thin Profile Extrusion

The paper presents the development of the Finite Element model for simulation of thin aluminium profile extrusion of both solid and hollow shapes. The analysis has shown that the material flow in simulation is very dependent on the friction model. Experimental and theoretical studies show that friction traction on the interface between the tool and the deformed material can be represented as a combination of adhesive friction force and the force that is required to deform surface asperities. In aluminium extrusion we can clearly distinguish two different areas with respect to friction conditions. The first area covers the inner surface of the container, feeding channels and pockets. Here the contact pressure is very high and the deformation friction factor is close to 1. The second area is the bearing. In this area we deal with combinations of different friction models in sticking, sliding and transient zones. The sticking zone has predominantly deformation friction. It is situated at the entrance to the bearing and may extend when the bearing has a choke angle. Thus the lengths of these zones are also dependent on variation of the choke angle and actual thickness of the profile. To get these values the material flow problem is to be coupled with the simulation of the tools deformation. A series of experiments with specially designed tools have been done to investigate how the bearing length and choke angle may influence the extension of different friction zones and by these means vary the material flow pattern. The friction models have also been tested with industrial profiles of complex shapes and have shown good correspondence to reality.