FEM SIMULATIONS OF FLOW THROUGH PORTHOLE DIES FOR EXTRUSION OF ALUMINIUM

ABSTRACT Three-dimensional nonlinear FEM (Finite Element Method) simulations have been applied to the study of the flow through porthole dies for aluminium extrusion. The applied model for the stress-strain relationship is based on mechanical tests, and has been verified by comparing press trials with simulations. A commercially available flow simulation program has been used for building the models, and the calculations have been performed using common workstations. Particle velocities, temperature fields and pressure fields are obtained by the modelling. The analyses are transient, and thus allowing to study the time dependencies of all parameters of interest. From the calculated results it is possible to quantify important aspects related to die design. The calculations do also support the general understanding of the process, and common problems related to the process. Critical studies can be made of the flow in the outlet region and the welding zones in order to get a better understanding about how these factors influence the process stability. Further, it is possible to trace the paths of any particle in the material through the die. The temperature and the deformation history of a material element during the extrusion process are known to influence grain growth and particle dissolution, and thereby the physical properties of the extruded material. This gives the opportunity to combine results from the thermo-mechanical simulations with metallurgical models to improve the understanding of the relations between die design aspects and product quality.