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Influence of the forming pre-strain on the fatigue performance of upset bulge formed tubes
BECHLER Jan, WEBER Florian, BULZAKOVSKI Tose, VÖLLMECKE Jörg, SULAIMAN Hosen, TEKKAYA A. Erman
download PDFAbstract. Safety-relevant components in the automotive industry must fulfill stringent requirements for performance, particularly in endurance. The height adjustment system in a car seat is one example. The height adjustment system is made up of sheet metal parts which are joined with steel tubes through axial compression – also referred to as upset bulge forming. As a result of the forming process, initial cracks occur at the inner bending radius of the tubes which, along with the forming history, decrease the fatigue life by 450%. The aim of this study is to identify whether the initial cracks occur due to shear bending generated by the process or elastic springback. The influence of the elastic springback on the crack initiation is investigated through bending experiments of DP600, Al99.5, and 1.4301. To prevent elastic springback, the specimens are secured with screws post-bending and are removed afterwards. The bending radius is investigated with respect to the equivalent plastic strain to determine a minimum without failure. Cyclic tests of bulges with two different forming histories are tested to investigate the influence of the forming pre-strain on the fatigue behavior. In all bent materials, initial cracks occur at the inner bending radius where the elastic springback increases the initial cracks and Scanning Electron Microscopy (SEM) analysis confirms shearing as the cause. It was also found the grain shape and orientation have a significant influence on the crack propagation in the forming zone of the tube through the upset bulging process.
Keywords
Fatigue, Forming Pre-Strain, Upset Bulging
Published online 4/24/2024, 9 pages
Copyright © 2024 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: BECHLER Jan, WEBER Florian, BULZAKOVSKI Tose, VÖLLMECKE Jörg, SULAIMAN Hosen, TEKKAYA A. Erman, Influence of the forming pre-strain on the fatigue performance of upset bulge formed tubes, Materials Research Proceedings, Vol. 41, pp 968-976, 2024
DOI: https://doi.org/10.21741/9781644903131-106
The article was published as article 106 of the book Material Forming
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
References
[1] P. Grützner, Prozessentwicklung für das Fügen durch Knickbauchen, Winter Industries, 2014.
[2] I. Sizova, A. Sviridov, and M. Bambach, Avoiding crack nucleation and propagation during upset bulging of tubes, International Journal of Material Forming 10 (2017) 443–451. https://doi.org/10.1007/s12289-016-1292-9
[3] N. Triantafyllidis, A. Needleman, and V. Tvergaard, On the development of shear bands in pure bending, International Journal of Solids and Structures 18 (1982) 121–138. https://doi.org/10.1016/0020-7683(82)90021-X
[4] J. A. Haley and S. Kyriakides, Bending induced wrinkling and creasing in axially crushed aluminum tubes, International Journal of Solids and Structures 202 (2020) 368–383. https://doi.org/10.1016/j.ijsolstr.2020.06.003
[5] A. Sviridov, P. Grützner, M. Rusch, and M. Bambach, Joining by upset bulging–tooling design and new concepts for online process control using servo presses and local heating, Journal of Machine Engineering 17 (2017) 78–87.
[6] 6892-1: 2017-02, Metallische Werkstoffe-Zugversuch-Teil 1: Prüfverfahren bei Raumtemperatur (ISO 6892-1: 2016), 6892-1, DIN 6892-1 (2017).
