Solid-state welding takes place during the extrusion of hollow shapes and tubes made from selected metals such as aluminum and magnesium and their alloys. In this thesis, an industrial extrusion trail with the extrudate of the "Double Hat" hollow shape has been examined. The process parameters of this trail have been employed into finite element simulation as initial settings then. DEFORM(TM) is one of the most frequently used FEM software packages to analyze the metal flow in deformation processes. This software has been used as the main tool of the simulations for this work. However, it has some limitations while applied to study the extrusion welding. Both of the 2D and 3D versions of DEFORM(TM) cannot determine if extrusion welding takes place in a port-hole die. This limitation is a result of a lack of ability to transfer the localized deformation conditions to a judgment about a good or poor weld. In the meantime, the collection of the information about localized state variables in the welds is inaccurate. In this study, a new modeling method has been proposed to obtain the localized information at the extrusion welding seam. A so-called pressure plate was virtually inserted in the position of the extrusion welding seam, which plays a role of a sensor and has been recording all the information at the given seam during the entire extrusion process. Analytical methods have been utilized to study the data collected from this sensor to evaluate the probability of the formation of the sound extrusion welding seam. The generated results have been used to verify Plata & Piwnik extrusion welding criterion and can be implemented into existing extrusion models to achieve better prediction of weld integrity.
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