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Manufacture of tailored tubes at elevated temperatures by heat assisted incremental tube forming

Thursday (09.11.2017)
11:15 - 11:35
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Titanium (Ti-2) and Titanium-Alloys (Ti3Al2.5V) have a manifold range of use in the aerospace (Boyer, 1996). Due to the limited formability and high strength, the manufacturing of tailored products is often realized by individual segments, which are joined by welding. The proposed heat assisted incremental tube forming (ITF) technology is a new approach to enable the manufacturing of complex shaped products out of a single workpiece. Core of the technology is the combined spinning and bending, which are applied to adapt the tube diameter, wall thickness and to bend a three dimensional curvature simultaneously. The contribution shows the technological extension of the ITF process (Becker, 2014), as well as the main effects of the heat assistance on the bending process and achievable product properties.

To improve the formability of the titanium alloys , an induction heating system is integrated into the spinning unit. Thereby, the time of applied heat is reduced to a minimum, so that favourable forming properties are achieved and softening of microstructure is avoided. The spinning and bending at elevated temperatures results finally in strongly reduced spring-back, geometrical deviations and extended process limits. Due to the compressive stress superposition through the combined spinning and bending, already at room temperature an enormous reduction of bending stress can be observed (up to 95%). The low bending force is further reduced by the heat assistance so that secondary effects as the gravity forces or mass inertia become a significant influence. Beside the experimental analysis, the governing process parameters as the temperature and process speed are studied also by numerical simulations. Finally, the produced demonstrators reflect the high flexibility of the process to design tailored tubular structures for the aerospace industry, which also facilitate the setting of product properties by the in-situ heat treatment.

Gallus Stefan
TU Dortmund University
Additional Authors:
  • Christian Löbbe
    University of Dortmund
  • Dr. Nooman Ben Khalifa
    University of Dortmund
  • Martin Seibt
    PFW Aerospace GmbH