Flow stress measuring by use of cylindrical compression test and special application to metal forming processes

In recent years the finite-element-method (FEM) simulation has become appli cable for the development, design and optimisation of metal forming process es. To obtain accurate results within the simulation the exact description of the flow stress kr during the process is essential. The implementation o f the flow curve into FE-packages can be realised through different methods . Using the measured data in tabular form seems to be the easiest way, but special interpolation methods are necessary and extrapolation is strictly f orbidden. Hence the exact flow stress measurement up to highest strain rate s (between 0.0001 and 300/s) to simulate industrial processes like rolling or extrusion is essential. This paper presents actual studies in the field of high-speed testing by use of a servohydraulic testing system in a temper ature range between room temperature and 1300 degreesC. Furthermore the use of material models to describe the material behaviour is getting more and more popular. Therefore hot compression tests must be carried out to determ ine the necessary parameters for reliable prediction. Specifically for alum inium alloys, where homogeneous deformation in the temperature range above 300 degreesC is not possible at present, new strategies for the determinati on of the material models have been developed. The compression tests are de liberately performed under sticking conditions to obtain strong gradients o f the forming and microstructure parameters within a sample. The model equa tions are then adapted by consideration of the local parameters. Finally an optimisation coupled with an FEM program is applied to the models.