Development and Validation of a Heat Generation Model for Friction Press Joining

摩擦压接技术（FPJ）是一种用于将热塑性聚合物与金属片以重叠形式连接的创新技术。它最初是由位于德国奥托布伦的空中客车创新工厂和慕尼黑工业大学（TUM）的机床和工业管理研究所（iwb）合作开发的，对于轻量化设计概念的发展来说，它是一项特别有前途的技术。该工艺与搅拌摩擦焊（FSW）非常相似，只是工具只有一个肩，材料没有混合。在工具-肩界面产生的热量被传导到金属-聚合物界面，导致聚合物熔化。冷却后，聚合物固化，连接完成。由于热塑性聚合物能够在较窄的温度范围内熔化而不发生降解，因此控制金属-聚合物界面温度的能力对于确保可靠的连接过程至关重要。目前，还没有关于FPJ热建模的文献。尽管已经发表了大量关于FSW产热建模的文献，但与这些过程相关的温度范围存在很大差异，研究表明FSW产热机制可能与FPJ产热机制不同。该项目的目标是能够为FPJ用户提供必要的方法来确定合适的工艺参数（重点是进料速度、转速和轴向力），以便在金属-聚合物界面产生所需的温度。实现这一目标的第一步是评估接触条件，并创建一个半解析模型来预测，例如，基于工艺参数的摩擦系数。然后对该模型进行调整和实施，以确定FPJ工具上任何给定点的热量产生，并描述工具表面热源分布的形状。生成的模型将通过采用简化和完整的FPJ设置的实验试验来支持和验证。此外，还将推导出一种测定金属-聚合物界面热传递的方法。关于热源分布的数值解将用于评估模型的有效性。此外，基于模拟的参数研究将用于构建从工具-工件界面到金属-聚合物界面的热量传递的元模型。在采取这些步骤之后，用户将能够根据工艺参数预测金属-聚合物界面的时间-温度分布。在最后一步中，模型将以相反的方式耦合和评估，以便为用户提供合适的工艺参数，以在金属-聚合物界面上生成所需的时间-温度剖面。

Friction Press Joining (FPJ) is an innovative technology used to join thermoplastic polymers with metal sheets in overlap configuration. It was first developed in a collaboration between Airbus Innovation Works in Ottobrunn (Germany) and the Institute for Machine Tools and Industrial Management (iwb) of the Technical University of Munich (TUM) and it is an especially promising technique for the development of lightweight design concepts. The process is very similar to Friction Stir Welding (FSW), only the tool consists of only a shoulder and the materials are not mixed. Heat generated at the tool-shoulder interface is conducted to the metal-polymer interface, causing the polymer to melt. Upon cooling, the polymer solidifies and the joint is complete. Because of the narrow temperature range, in which thermoplastic polymers are able to melt without undergoing degradation, the ability to control the temperature at the metal-polymer interface is critical to assure a reliable joining process. Currently, there is no literature available pertaining to the thermal modeling of FPJ. Although a vast amount of literature has been published regarding the modeling of heat generation in FSW, the temperature ranges pertinent to these processes are vastly different, and research suggests that the mechanisms for heat generation in FSW process may be different than those for FPJ. The goal of the proposed project is to be able to supply an FPJ user with the methods necessary to determine the suitable process parameters (focus on feed rate, rotational speed, and axial force) in order to produce a desired temperature at the metal-polymer interface. The first step in achieving this is to assess the contact conditions and create a semi-analytical model to predict, for example, the friction coefficient based on the process parameters. This model will then be adapted and implemented in order to determine the heat generation at any given point on the FPJ tool and to describe the shape of the heat source distribution over the tool surface. The generated models will be supported and validated by experimental trials employing simplified and full FPJ setups. Additionally, a means of determining the heat transport at the metal-polymer interface will be derived. Numerical solutions concerning the heat source distributions will be used to assess the model validity. Additionally, a simulation-based parameter study will be used to construct a metamodel of the heat transport from the tool-workpiece interface to the metal-polymer interface. After these steps have been taken, the user will be able to predict the time-temperature profile at the metal-polymer interface based on the process parameters. In the final step, the models will be coupled and assessed in an inverse manner in order to give the user the suitable process parameters to generate a desired time-temperature profile at the metal-polymer interface.