PSI - Issue 13

918 Markus Könemann et al. / Procedia Structural Integrity 13 (2018) 914–919 Markus Könemann/ Structural Integrity Procedia 00 (2018) 000–000 5 In the first case, the eccentricity �� ( 1 ) of the elliptical notched sample is continuously adjusted. The Lode angle is in the range of approximately 1 and the stress triaxiality is evaluated by analyzing the time at which the sample is geometrically softened. A procedure based on the Considère criterion is used to determine this point. The force displacement curve of the relevant geometry is analyzed in elastic-plastic simulations. The stress-strain curve is then determined from the first main normal stress and the derivation of this curve is created. At the point where the stress strain curve and the derivative meet, the triaxiality is evaluated. This procedure is repeated for many variations of eccentricity and applied in a diagram. A compensation curve is created by the applied simulation results, so that a corresponding eccentricity can be selected directly if the desired triaxiality is known. �� � �� � � � ( 1 ) In the second case, the method for determining the stress triaxiality for plane strain samples is repeated. Now the radius of the notch is varied without changing the narrowest distance of the specimen. Here, a function is created that The new test procedure will help to facilitate the design of new components made of sheet metal materials. It is therefore necessary to carry out material simulations that describe the material behavior as precisely as possible. However, a pure von Mises plasticity is therefore not precise enough. For this reason, simulations were carried out in this study using a material model that takes into account the influences of stress triaxiality and Lode angle parameter. The modified Bai Wierzbicki model, which due to its modular design also allows the consideration of temperature and strain rate effects, is therefore used in this study. More detailed explanations of this model can be found in (Bai & Wierzbicki, 2008) and (Lian, Sharaf, Archie, & Münstermann, 2012). Damage to the material was not initially considered. A high-strength DP1000 is used as the test material. The parameters used are listed in Table 1. �� �� �� m �� �� �� �� �� �� 0,95 1,0 0,9 6 9,0 0,035 1,05 0,003 1,0 0,0006 allows the selection of a radius at a given triaxiality. 4. Simulation based investigation tensile impact tests Table 1. Parameters of the calibrated modified Bai Wierzbicki model for DP1000

Fig 6. Comparison of force and displacement for a tensile impact test with simulation and experiment