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

本研究项目是基于这样一个研究假设，即通过感应加热，可以可靠地加工高强度材料，可以显著降低切削力，通过精冲可以提高零件质量。因此，精冲的制造过程可能需要了解和解释剪切带中的热机械机理。加热金属板材会产生较低的流动应力，从而促进塑料材料的流动，并减少精切削过程中所需的加工力。通过降低冲裁力，精冲工艺将有资格加工更厚的板材，并为加工超高板材提供了额外的可能性。对于精冲来说，板材加热、冲裁力、可实现的部件质量以及对精密热机械机制的了解之间的相互作用是未知的。为了证实这一研究假设，将进行实验和数值研究。利用该系统对16MnCr5、42CrMo4等金属薄板材料进行了TTH25不同加热方式的试验研究。此外，还将对不同的电感设计进行试验，以分析精冲过程中热分布的影响。通过分析截面质量(显微组织、表面质量)及其与加热曲线和工艺特征(冲裁力、V形环力、反作用力)的关系，描述了其热力学作用机理。数值有限元过程模拟支持实验方法，以允许进一步关联应力-应变状态和其他难以测量的量(真实应变)。所有部分结果(冲裁力减小率、截面质量、静水应力状态、伸长率)相互结合，形成一个考虑板材厚度、板材和热机械作用机理的整体解释模型。目的是扩展带温度因素的精冲工艺的冲裁力、V形环压力和反力的计算范围。这允许作为温度的函数的过程力的解析计算。此外，还将推导出不同的经验解析函数曲面，它们反映了加热温度、零件质量和零件性能之间的函数关系，这些函数曲面考虑了板材、板厚和静水应力状态。这样，假设的研究假设被检验，并与解释模型的验证相结合，将实现更好的研究目标。

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.