Extrusion as a metal forming process has previously been dealt with in Sec. 2.2.5 and Ch. 18. In Ch. 12, commonly used experimental grid pattern techniques were described, and it was shown that such techniques are required in order to be able to describe the deformations occurring in forward and backward extrusion. The treatment showed that metal flow and deformational behavior in the extrusion processes are indeed complex.

It will now be shown how simple axisymmetric aluminum extrusion can be modeled by FEA, with respect to both forward and backward extrusion. A comparison of results obtained by means of simulation models with corresponding results from experimental grid pattern analysis confirms that these simulations describe the real metal flow in extrusion with good accuracy. Finally, the FEM models are used to show some differences in deformation characteristics in forward and backward extrusion.

Forward Extrusion of Aluminum

Forward Extrusion Divided into Subprocesses

A new concept has been proposed to explain the complex metal flow phenomena taking place in the unlubricated forward extrusion process, as applied for hot extrusion of Al and Al alloys. The concept is based on considering the process to be partitioned into four subprocesses. Then, by FEA, it is possible to model and to analyze each of the four different subprocesses by individual FEM models, which each describe particularly well the different deformation phenomena encountered in the forward extrusion process.