Numerical and experimental investigations of thermal riveting of polymeric materials

通过实验与仿真的对比，可以真实地记录和模拟影响热塑性铆接的几何结构、材料和工艺技术因素。数值模型的使用应增加过程的透明度，并应导致可管理的塑料铆接接头的设计标准。热铆接方法的分类是基于能量输入的类型，如热空气铆接（对流）和热成形（热传导）。基于实验确定的材料行为，数值模型的开发，模拟热铆接过程接近现实。其目的是表征加热和成形行为之间的特定过程相互作用，并将它们与所得材料结构联系起来。此外，机械连接性能必须与使用FEM的不可测量或难以测量的物理参数（例如应力、应变）相关联。这些物理参数取决于所使用的铆销几何形状、压模设计和工艺参数。此外，在模拟和实验室测试中确定的准静态强度特性将被转移到动态载荷下的操作行为。用模拟和实验确定的短期性能评价长期性能的限制条件，应得到科学的解释。为此，进行了振动测试（振动器），动态压头拉伸测试以及介质和温度影响下的长期研究。通过断裂力学分析、光学显微分析和热分析，对失效模式、失效过程和材料状态进行了表征。

Due to the comparison between experiment and simulation, the geometrical-constructive, material and process-technical factors influencing thermal plastic riveting can be realistically recorded and modeled. The usage of numerical models should increase the process transparency and should lead to manageable design criteria for plastic riveted joints. The classification of thermal riveting methods are based on the type of energy input like the hot air riveting (convection) and the hot forming (heat conduction). Based on the experimentally determined material behavior, numerical models have to be developed which simulate the thermal riveting processes close to reality. The aim is to characterize the process-specific interactions between the heating and forming behavior and to link them with the resulting material structure. Furthermore, the mechanical joining properties have to be correlated with the non-measurable or difficult-to-measure physical parameters (e.g. stress, strain) using the FEM. These physical parameters are depending on the used riveting pin geometry, the stamp design and the process parameters. In addition, the quasi-static strength characteristics determined in the simulation and in laboratory tests are to be transferred to the operating behavior under dynamic load. It should be scientifically explained, under which restrictions the short-term properties, determined by simulation and experiment, can be used to evaluate the long-term properties. For this purpose, vibration tests (shakers), dynamic head tensile tests and long-term investigations under the influence of media and temperature are carried out. Fracture-mechanical, light microscopic and thermal analyzes are done to characterize the failure modes, the failure process and the material condition.