Fraunhofer Institute for Mechanics of Materials IWM
Engineering (Mechanical engineering)
Natural Sciences (Physics)
The video shows the simulation of a tensile test. The tensile specimen is shown in a half-section. The color scheme represents the plastic strain occurring during the strain. The end of the videos shows a stress-strain diagramm of the simulation in comparison with the experiment.
The dynamical evolution of the yield stress is approximated by a Johnson-Cook model. The JC parameters are determined by an experiment using a 20MnCr5 tensile speciment that was carried out beforehand. Since the experiment was carried out with very low, quasi-static, strain rates, only the JC parameters for the plastic deformation are considered. No model for the material failure at high plastic deformations is applied.
The tensile specimen is 25mm long and has a diameter of 6mm in center. The resolution, and hence the initial particle spacing, is 0.2mm yielding 144'000 SPH particles. On both sides of the specimen tensioning pistons are applied that stretch the specimen with a constant velocity.
In comparison with the experimentally derived stress-strain curve, the numerical simulation can reproduce the stress states for a wide range of strains. For large strains, the numerically derived values deviate from the experiment due to the calculation of the technical stress which uses the constant initial cross section in the center of the specimen and therefor can not account for the necking area for large strains. This underestimates the stress states for high technical strains.
This numerical investigation was carried out using SimPARTIX.
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