T. Hammers

Influence of Mandrel s Surface on the Mechanical Properties of Joints Produced by Electromagnetic Compression

Electromagnetic compression of tubular profiles with high electrical conductivity is an innovative joining process for the manufacturing of lightweight structures. Taking conventional interference fits into account, the contact area’s influence on the joint’s quality seems to be of significance, as e.g. the contact area and the friction coefficient between the joining partners determine an allowed axial load or torsional momentum proportionally. Therefore, different contact area surfaces were prepared by shot peening and different machining operations and strategies. The mandrel’s surfaces were prepared by shot peening with glass beads and Al2O3 particles. Alternatively, preparation was done using simultaneous five axis milling, because potential joining partners in lightweight frame structures within the Transregional Collaborative Research Centre SFB/TR10 would be manufactured similarly. After that, the manufactured surfaces were characterized by measuring the surface roughness and using confocal whitelight microscopy. After joining by electromagnetic compression, the influence of different mandrel’s surface conditions on the joint’s mechanical properties were analyzed by tensile tests. Finally, conclusions and design rules for the manufacturing of joints by electromagnetic compression are given.

Prototype Manufacturing of Extruded Aluminum Aircraft Stringer Profiles with Continuous Reinforcement

For an increase in safety against crack initiation and growth in metallic structures of airplanes different concepts were developed in the past. In the focus of this work are profiles made of continuously reinforced extruded aluminum. The production and the used die set of these profiles is presented as well as problems occurring in terms of geometrical inaccuracies of the embedded high strength wires. In addition, this paper attends to the problem of lateral seam weld formation. The interface between the AA-2099 as well as AA-6056 aluminum alloy and the high strength wires Nivaflex and Nanoflex were characterized by metallurgic investigations and push-out tests. As a result it can be stated that a sufficient geometrical accuracy could be achieved and a high interface strength can be accomplished even if a slight gap is still present in the interface layer between matrix and reinforcing element.