Electromagnetic Form-Fit Joining

As a way to reduce a vehicle's weight, the application of space frame structures has been increasing. This innovative lightweight design concept is already commonly applied in the low volume production of cars. Due to the high stiffness and low mass, extruded aluminum profiles are particularly suitable for the manufacturing of such structures. But the potential for great weight reduction using space frames is curtailed by the difficulties associated with manufacturing the space frames. These structures have complex demands on joining technologies, and conventional processes often are pushed to their technological limits. A promising alternative to connect extruded aluminum profiles without heating or penetration is joining by electromagnetic crimping. Compared to adhesive bonding and welding, the process also requires a less extensive preparation of the joining zone. This technique is characterized by the use of pulsed magnetic fields to form a profile made of an electrically conductivity material into form-fit elements, like grooves, of the other joining partner. Thereby, an interlock is generated which enables the load transfer. However, existing process and joint design methodologies require either sophisticated numerical modeling or extensive experimental studies. The influence of some major process and joining zone parameters, like the forming direction and the groove shape, on the joint strength is also still unknown. Additionally, it has not been analyzed how a mass reduction in the joining zone and the resulting change of the radial strength of the joining partners affects the crimping process and the transferable load. Therefore, a fundamental process understanding of the manufacturing and the load transfer of form-fit connections manufactured by electromagnetic crimping is developed in this thesis. Based on analytical, experimental, and numerical studies, major parameters are identified and their influence on the joining process and the achievable joint strength is analyzed. For the analytical investigations a continuous approach describing the manufacturing of the connections as well as the load transfer is introduced here. This model also facilitates the process and joining zone design of electromagnetically crimped connections. Furthermore, a process window considering the influence of a mass reduction in the joining zone on the connection strength is developed based on the experimental results and the analytical approach.