Aluminium extrusion investigated by theory, experiment and FEM-analysis
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The process of aluminium extrusion has important influence in metal forming industry because of its ability to produce profiles with different shapes, sizes and complicated geometries. The required extrusion load is depending on the process parameters such as the flow stress of the billet material, velocity field, strain rate distribution, and thermal conditions within extrusion. These conditions are so important for industries, and interesting for academia, that research has been performed since many years to develop better understanding about extrusion. The first aim of this research work has been to gain increased understanding about extrusion welds, deformation characteristics and required extrusion force when extruding aluminium at hot conditions. During the study it is focused on the topic of gas pocket formation in porthole die, the velocity fields establishing and developing, strain rate distributions, thermal conditions and extrusion force. Further it was aimed to simulate an industrial and laboratory extrusion set up, validated by experiments and compares it with the available theory. It has been shown that finite element analysis today is n excellent tool to investigate the load stroke characteristics, velocity fields and strain distributions within the billet (workpeice) while extruding. Initially the challenge was to map and address the questions about extrusion welding, extrusion load and the extrusion process parameters by use of DEFORM 2D, but as the work preceded the study was expanded by including 3D situations of extrusion corresponding to what is occurring in industrial extrusion.