LAUSR

Abstract The description and modelling of the forming behaviour is essential for the numerical prediction of material flow and the applied forming force. A representative stress state as well as comparable strain rate and temperatures should be considered during material characterization. In the presented investigations, an extruded aluminium alloy (EN AW-6060 T6) was formed for different compression tests with diverse specimen geometries (cylinders, discs, flat rings, cuboids) and compared with the tensile and torsion tests under the same forming conditions and with one and the same initial microstructure with an average grain size of 50 µm. To ensure that no microstructural changes during the deformation process (recrystallization) affect the measurement results due to load-related material anomalies, all tests for the material characterization were started at room temperature. The comparison is based on the cylindrical compression test, because this is standardised for room temperature (DIN 50106) and, due to the compressive stress, is the most suitable material description for bulk forming processes. However, in the stacked compression tests without additional guide elements, a much higher friction between the layers is required than between the workpiece and the tool, so that the deformation is not concentrated on the centre of the specimen (with regard to height) and the middle layers won’t get out due to high tangential stresses. By consideration of these conditions the stacked tests are comparable to the cylindrical compression test. However, the friction between material and die must be taken into account for compression tests as well as the resulting forming heat when calculating the flow curve. Based on this, the forming behaviour can be modelled according to various flow curve approaches for cold forming processes. In general, it was found that all flow curves of the tensile tests, torsion tests and the compression test were in the range of ± 7.5 % based on the cylinder compression test.