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Engbert, T.; Heymann, T.; Biermann, D.; Zabel, A.:
In: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 225 (2011) 3, S. 398-407
Light-metal extrusions are widely used as frame-structure elements. Joining these profiles via screw coupling is a challenging task due to the small wall thickness of the extrusions and the missing accessibility within a frame structure. The combination of flow drilling and thread forming offers a possibility to cope with this task. These processing techniques allow the manufacture of stable threads in thin-walled structures with the profile accessible from one side only. Nowadays, aluminium profiles can be continuously reinforced through composite extrusion. Mechanical properties, like increased tensile strength compared with homogeneous profiles, make reinforced profiles preferable for applications such as safety-relevant components. However, the reinforcement can seriously affect machining processes as well as the machining results. Therefore, the flow-drilling operation, the thread-forming operation, and the process results have been analysed in detail with a new, difficult-to-machine material combination, namely steel-wire-reinforced aluminium extrusions. The crucial factor when machining lightweight extrusions are the forces acting perpendicular to the thin walls, so the influence of the reinforcement and the processing parameters on the feed force during flow drilling is presented. To examine the effect of the reinforcement on the thread-forming result and to quantify the benefit of flow drilling, the threads are stressed with a defined tensile load until failure.