Numerical modelling of the aluminium extrusion process when producing complex sections

摘要

This thesis reports the analysis by FEM of both continuum and structural models describing the extrusion process. They were compared with experimental work and the agreement is satisfactory. All the simulations were performed with the implicit finite element code Forge2009® with user input written in Visual Fortran®. Alloys AA2024 and AA6063 were utilised as the source materials in order to compare with published experimental work. The Forge2009® 2D module was used to investigate both direct and indirect axisymmetric rod extrusions. The extrusion load and the temperature rise were predicted and the load-displacement curves and the events that took place in both extrusion modes were also simulated, discussed and again verified. The effects of the difference between the two modes, especially friction and its consequences on the process were investigated. The indirect results point to a good method of improving efficiency. For complex solid section, the 3D module has been used to study the load required, temperature evolution, surface formation of the extrudate and material flow during the process. These all showed good correlation with experimental results. The microstructure evolution during the extrusion process and the following solution soaking process were simulated with physically-based mathematical microstructure models integrated into FEM through its Fortran® subroutine interface,. The agreement between the predicted microstructures using associated models and experimental measurements were acceptable. For hollow section, the emphasis was placed on the study of the complicated metal flow and the seam welding quality. Novel analyses were developed to analyse the metal flow.