The aluminium extrusion process is a forming process where a billet of hot aluminium is pressed through a die to produce long straight aluminium profiles. A large variety of products with different and complex cross-sections can be made. The insight in the mechanics of the aluminium extrusion process is still limited. Design of extrusion dies is primarily based on trial and error. The wasted scrap and time in these trail and error iterations, can be reduced by gaining more insight in the extrusion process. Numerical analysis is a valuable tool in obtaining that insight. In this thesis reports new developments for the analysis of the aluminium extrusion process are treated. The subject matter is presented in four chapters. Attention is focussed on three topics: • A comparison between experiments and simulations of container flow • Modeling the start-up of the extrusion process in an Eulerian formulation • Deriving a new finite element for ALE simulations Extrusion experiments have been performed at Boalgroup to visualize the flow inside the container during extrusion. These experiments are compared with simulations. The results of the simulations are steady state results that are post-processed to be comparable to the experimental results. If the simulations are not in agreement with the experiments, the material properties used in the simulations are adapted so the results agree. With this method it is possible to determine material properties under extrusion conditions. Correcting the dies after trial pressings is performed by die-correctors. The correctors use the first part of the profile (nose piece) to asses the work that has to be performed on the die. To be able to model this nose piece, is very valuable during designing of the die. In chapter 4 and 5 new strategies to simulate the shape of the nose piece are treated. In the last chapter the possibilities of the proposed strategy are demonstrated on a porthole die for a tube. The simulated nose piece is in very good agreement with the experimental results.
|Award date||11 Jun 2009|
|Place of Publication||Enschede, The Netherlands|
|Publication status||Published - 11 Jun 2009|