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Abstract
Surface cracking is generally recognised as one of the main defects occurring during the process of aluminium extrusion, especially in the case of the so called hard aluminium alloys. Previous experiments suggest that this type of defect is caused by the rise in temperature as the process proceeds. Some experiments indicate that the surface quality is good even though the temperature may be high during extrusion. It is also well known that crack criteria have been adopted to explain the cracking that occurs in extrusion, blanking and rolling, etc. In this study, a finite element method (FEM) is used in different ways to predict surface cracking during hot extrusion. The crack criteria are integrated into the FEM code FORGE®2.0. The effectiveness of these criteria in predicting surface cracking in the case of hot extrusion is discussed. The FEM simulation also provides some other quantitative data, such as the temperature rise during extrusion from different initial temperatures. In addition, the principal stresses at the die land area at different extrusion stages are also shown.