Investigation of the thermomechanical interactions in the shear zone during the fine blanking of heated high strength sheet materials (HotFib)

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The research project is based on the research hypothesis that by means of inductive sheet heating, high-strength materials can be processed reliably, the cutting force can be significantly reduced and the component quality can be improved by fine blanking. Thus, the manufacturing process fine blanking may be capable of the thermo-mechanical mechanisms need to be understood and explained in the shear zone. Heating the sheet metal leads to a lower flow stress, which promotes the plastic material flow and reduces the necessary process forces during fine cutting. By lowering the blanking force, the fine blanking process will be qualified for processing thicker sheets and offers additionally the possibility to process ultra-high sheet metal materials. The interactions between the heating of the sheet material, the blanking force, the achievable component quality as well as the knowledge of the precise thermomechanical mechanisms is unknown for fine blanking. In order to confirm this research hypothesis experimental and numerical investigations will be carried out. By means of the system TTH25 different heating profiles will be applied to sheet metal materials (16MnCr5, 42CrMo4). Furthermore, different inductor designs will be tested in order to analyze the influence of the heat distribution during the fine blanking process. The thermomechanical mechanisms of action are described by analyzing the section quality (microstructure, surface quality) and their correlation with the heating profiles as well as the process characteristics (blanking force, v-ring force, counter force). The numerical FE process simulations support the experimental methods to allow further correlations with the stress-strain state and other difficult to measure quantities (true strain). All partial results (blanking force reduction, section quality, hydrostatic stress state, elongations) are combined with each other to form a holistic explanation model considering the sheet thickness, the sheet metal material and the thermomechanical mechanisms of action. The aim is to extend the calculation of blanking force, v-ring force and counter force for the fine blanking process with a temperature factor. This allows the analytical calculation of the process forces as a function of the temperature. Furthermore, different empirical-analytic function surfaces will be derived that reflect the functional relationship between heating temperature, part quality and part properties considering on the sheet material, the sheet thickness and the hydrostatic stress state. In this way, the postulated research hypothesis is examined and, in conjunction with the validation of the explanation model, the superior research objectives will be achieved.