TP4: Interactions of thermal phenomena with the formation of adiabatic shear bands in high-speed blanking

本课题组的研究假设是基于绝热剪切带的形成与热边界条件的依赖性这一假设。这是最大工艺温度（T）和热冲击（T_punkt），即温度曲线的时间导数，与熔化温度和片材的热膨胀系数（T_S和α_s）相互作用。目的是建立一个唯象模型，该模型结合参数Ts，T和T_punkt与α_s，描述了材料特有的下限变形速度之间的相互关系，在该速度之上，绝热剪切带的形成发生。此模型还允许对其他材料和板材属性（如板材厚度）进行内插或外推。结果也被用来研究动态再结晶理论，其中剪切带的形成是直接相关的再结晶温度，这与各自的熔化温度。一种创新的方法，包括一个实验工具上使用的机械冲压机和测量技术的基础上热电，可以确定这些参数。在测量设置中使用热电技术，可以在有源元件的切割边缘进行即时、现场温度测量。这种瞬时测量方法可以确定高速冲裁过程中的热冲击（T_punkt）。预热板允许通过减小变形开始和绝热剪切带形成时间之间的温差来影响热冲击。通过使用特殊的插入物提供对成形区的光学访问，高速相机可用于记录裂纹扩展以及应变和应变率，从而评估剪切带的形成。熔融温度参数（T_S）可以通过改变片材材料来影响。不同的合金用于此目的-从低熔点金属如锡和锌到铝合金EN AW-5754和钢材料如22 MnB 5。

The research hypothesis of this subproject within the research group is based on the assumption of a dependence of the formation of adiabatic shear bands on thermal boundary conditions. This is the maximum process temperatures (T) and the thermal shock (T_punkt), i.e. the time derivative of the temperature profile, in interaction with the melting temperature and the coefficient of thermal expansion of the sheet material (T_S and α_s). The aim is to develop a phenomenological model that describes the interrelationships of the material-specific, lower limit deformation speed, above which the formation of an adiabatic shear band occurs, combined with the parameters T_S, T and T_punkt with α_s. This model also allows interpolation or extrapolation to other materials and sheet properties, such as sheet metal thickness. The results are also used to investigate the theory of dynamic recrystallization, in which shear band formation is directly related to the recrystallization temperature, which correlates with the respective melting temperature. An innovative method consisting of an experimental tool for use on a mechanical stamping press and a measurement technique based on thermoelectricity, allows the determination of these parameters. The use of thermoelectricity in the measurement setup enables instantaneous, in-situ temperature measurement at the cutting edge of the active elements. This instantaneous measurement method makes it possible to determine the thermal shock (T_punkt) during a high-speed blanking process. Preheated sheets allow influencing the thermal shock by reducing the temperature difference between the start of deformation and the time of the adiabatic shear band formation. By using special inserts that provide optical access to the forming zone, a high-speed camera can be used to record crack propagation, as well as strains and strain rates, and thus evaluate shear band formation. The melting temperature parameter (T_S) can be influenced by varying the sheet material. Different alloys are used for this purpose – from low melting metals such as tin and zinc to the aluminium alloy EN AW-5754 and steel materials such as 22MnB5.