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Influence of weld imperfections on the fatigue behaviour of resistance spot welded advanced high strength steels

: Rethmeier, M.


Clark, G.:
Fatigue 2014, 11th International Fatigue Congress. Pt.2 : Selected, peer reviewed papers from the 11th International Fatigue Congress 2014, March 2-7, 2014, Melbourne, Australia
Durnten-Zurich: TTP, 2014 (Advanced materials research 891-892)
ISBN: 978-3-0383-5008-8
International Fatigue Congress <11, 2014, Melbourne>
Conference Paper
Fraunhofer IPK ()

The use of advanced high strength steels (AHSS) in the automotive body-in-white is increasing. Those steels are predominantly joined by resistance spot welding. For the performance of the whole body-in-white, the fatigue behaviour is of high interest, especially as during production, weld imperfections such as cracks and manufacturing-related gaps cannot be avoided. In this study the TRIP steel HCT690 was used as it is a typical advanced high strength steel in automotive production. The investigation into the influence of cracks was split depending on the crack location in the weld area. Surface cracks in the electrode indentation area as well as in the heat affected zone were produced during welding and analyzed. The results showed that surface cracks independent of their position have no effect on the fatigue life. The produced internal imperfections have shown only a marginal impact on the fatigue life. It was ascertained that gaps of 3 mm lead to a significant drop in fatigue life compared to gap free shear tension samples under a load ratio R of 0.1. This fact was attributed to decreased stiffness, higher transverse vibration and higher rotation between the sheets. Furthermore, FE-simulations have shown an increase in local stresses in gapped samples.