Zähigkeit von kaltumformbarem Stahlfeinblech

In the past, the toughness of high-strength sheet materials with product thicknesses below 2.5 mm has only been insufficiently investigated. In this thesis, therefore, an experimental technique is developed to determine the toughness of thin sheets. Especially thin sheets below a thickness of 1.5 mm can be investigated by impact tensile testing. For the investigations, a pendulum impact tester was equipped with an impact pendulum. An impact test was then carried out on notched flat tensile specimens to determine energy values. The impact tensile test on a dual-phase steel of the DP1000 grade showed a previously unobserved behaviour. It was determined that the impact strength of the initially tested samples showed no energy loss in the low temperature range. For this reason, further investigations were carried out to analyze the influence of the stress state on the energy absorption. For this purpose, a specific adjustment of the investigated stress state was carried out using various notched specimen geometries. As a result, it could be observed that the stress triaxiality had the greatest influence on the energy absorption potential of the material, while the temperature showed a decisive influence on the existing fracture mechanism. These theses are supported by extensive investigations in impact tensile tests and by fracture surface analyses in the scanning electron microscope. In the following, a method was then developed which allows the determination of toughness values in the impact tensile test in accordance with the component. For this purpose, a damage-mechanical material model was first calibrated, which takes into account the effects of temperature, strain rate and stress state. This model is the phenomenologically modified Bai-Wierzbicki model. The calibration of the model and necessary extensions are also part of this thesis. Furthermore, a method for computer-aided specimen generation based on a Python tool was developed. It is intended to identify specimen geometries that represent the stress state at the most stressed point of the considered component. For this purpose, the detail of a B-pillar was examined as an example, for which the method for the determination of toughness appropriate to the component was successfully tested. A correlation method was ultimately developed to link the new test technology to the Charpy-V-notch test. Different correlation possibilities were shown. On the one hand, a correlation of both tests is possible by means of comparable stress states via a ratio value based on the upper shelf behaviour. On the other hand, a comparison of the test results can be made by analysing the fracture surfaces. An extension of the impact tensile test to component-related geometries or semi-finished products could also be shown by adapting the testing technique for a seamless tube