Joint Design for Strut Connections in Airplane Structures Produced by Electromagnetic Forming

Electromagnetic forming offers high potential for producing high-quality joints of similar and dissimilar materials. This can be exploited e. g. in aircraft design for assembly of struts. In order to give insight in the interactions between different influencing parameters and their effect on the loadability of the resulting joint in electromagnetic form-fit joining, design of experiments was used in a comprehensive study. Groove parameters (shape, depth, width and edge radius) and the capacitor charging energy were varied in joining experiments considering tubes made of EN AW-2024 (T351) with an outer diameter of 70 mm and, a wall thickness of 1.6 mm together with end parts made of the same material with a diameter of 66.8 mm. The loadability of the resulting compound was evaluated considering axial compression force. One important finding was that triangular grooves can provide highest loadability if relatively deep grooves, well-adjusted groove width and suitable capacitor charging energy are applied. An optimized groove edge radius can contribute to further improvement of the loadability. Numerical simulations on different groove shapes were performed in order to study the development of the forming stages during the process and to explain the trends observed in the experimental study.