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Electromagnetic sheet metal forming is a high speed forming process using pulsed magnetic fields to form metals with high electrical conductivity such as aluminum. Thereby, workpiece velocities of more than 300 m/s are achievable, which can cause difficulties when forming into a die. The kinetic energy, which is related to the workpiece velocity, must be dissipated in a short time slot when the workpiece hits the die; otherwise undesired effects, for example rebound can occur. One possibility to handle this shortcoming is to locally increase the stiffness of the workpiece. A modal analysis is carried out in order to determine the stiffness of specific regions of the workpiece so that an estimation concerning the feasibility of the desired geometry is possible in advance without doing cost and time consuming experiments. Thereby, the desired geometry of the workpiece will be fractionized in significant sectors. This approach has to define the internal force variables acting on the cutting edge, which are required to constrain the numerical model. Finally, a method will be developed with the objective of calculating the stiffness of each sector. The numerical results will be verified by experiments.

A drop-weight high-speed tensile testing instrument was developed, in which the acting force and the specimen elongation can be obtained by measuring the displacement of the drop-weight by means of an optoelectronic transducer. The system was used to obtain the flow curves of AA5754 at strain rates up to 2,200 s -1 . The flow curves were verified with the help of finite element calculations by comparing the displacement and full-field strain measurement results. The developed instrument provides satisfying flow curves, in addition to being simple and cheap.

Three high speed tensile tests of the aluminum alloy AlMg3 and finite element (FE) simulations of these tests were performed. The strain rate dependency parameters for the Cowper-Symonds material model, which minimize the difference between measured and simulated displacement results, were determined. The verification of the determined parameters by means of strain distribution comparisons between an additional experiment and its simulation revealed the necessity for further consideration of the parameters.