PSI - Issue 2_B

Joern Berg et al. / Procedia Structural Integrity 2 (2016) 3554–3561 Joern Berg, Natalie Stranghoener, Andreas Kern, Marion Hoevel / Structural Integrity Procedia 00 (2016) 000–000

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1. For both loading types the slope of the S-N lines can be approximated with m = 3 for the as welded toe condition and m = 5 for the HFHP treated weld toe condition although most of the HFHP treated specimens of the VAL tests failed from crack initiation differing from the HFHP treated weld toes. 2. The results of specimens tested with maximum stresses close or even above the yield strength show a fatigue life increase due to HFHP treatment by factors of ~4 (transversal stiffener) and ~2 and ~5 (butt weld). In spite of the high maximum loads of the spectrum loading, the beneficial effect of the induced residual stresses due to HFHP treatment is not vanished. 3. The evaluation of the fatigue strengths of the CAL fatigue tests results with 50 % survival probability correspond to a FAT class increase by +9 FAT classes (butt weld) and +8 FAT classes (transversal stiffener) confirming existing design proposals for the consideration of HFHP treatment. 4. The real damage sums lie between D = 1.3 and D = 2.5 for the as welded toe condition and between D = 0.8 and D = 2.2 for the HFHP treated condition confirming the recommended damage sum of D = 0.5 according to Hobbacher (2016) as a conservative value for both weld toe conditions. The discussed results are part of an ongoing project and represent preliminary conclusions. Further VAL fatigue tests will be carried out for the notch details transversal, longitudinal stiffener, cover plate and butt weld with transition in thickness. Acknowledgements The authors want to thank DEPA Gesellschaft für Kranauslegerteile mbH, Leverkusen for welding the Berg, J., 2016. Zum Einfluss des Höherfrequenten Hämmerns auf die Ermüdungsfestigkeit geschweißter ultrahochfester Feinkornbaustähle (in German), PhD-Thesis, University of Duisburg-Essen, in preparation. Berg, J., Stranghöner, N., 2016. Fatigue behaviour of high frequency hammer peened ultra high strength steels, International Journal of Fatigue 82, 35-48. Dürr, A., 2007. Zur Ermüdungsfestigkeit von Schweißkonstruktionen aus höherfesten Baustählen bei Anwendung von UIT-Nachbehandlung (in German), PhD-Thesis, University of Stuttgart. Fischer, R., 1977. Eine dem stationären Gaussprozess verwandte Beanspruchungs-Zeit-Funktion für Betriebsfestigkeitsversuche (in German), VDI-Verlag, Düsseldorf. Gurney, T. R., 1991. The fatigue strength of transverse fillet welded joints. A study of the influence of joint geometry. Abington Publishing, Cambridge. Haagensen, P. J., Maddox, S. J., 2010. IIW recommendations on post weld fatigue life improvement of steel and aluminium structures, International Institute of Welding, Doc. XIII-2200r7-07. Hummel, H., 2003. Ermüdungsverhalten geschweißter Bauteile aus hochfesten Sonderbaustählen in Mobilkranen (in German), PhD-Thesis, University of Aachen. Hobbacher, A., 2016. Recommendations for fatigue design of welded joints and components, Springer International Publishing, Cham. Maddox, S. J., 2015. Allowance for bending in fatigue design rules for welded joints, International Institute of welding, Doc. XIII-2580-15. Melz, T. et al., 2015. Erweiterung des örtlichen Konzeptes zur Bemessung von LCF-beanspruchten geschweißten Kranstrukturen aus hochfesten Stählen (in German), Forschungsvereinigung Stahlanwendung e. V. FOSTA, Düsseldorf. Mikkola, E., Doré, M., Khurshid, M., 2013. Fatigue strength of HFMI treated structures under high R-ratio and variable amplitude loading, Procedia Engineering 66, 161–170. Stranghöner, N., Berg J., 2015. Einfluss des höherfrequenten Hämmerns auf die Ermüdungsfestigkeit ultrahochfester Stähle der Festigkeitsklassen S960, S1100 und S1300 am Beispiel geschweißter Kerbdetails (in German), Final report project P 938, Forschungsvereinigung Stahlanwendung e. V., FOSTA, Düsseldorf. Ummenhofer, T. et al., 2011. REFRESH - Lebensdauerverlängerung bestehender und neuer geschweißter Stahlkonstruktionen (in German), Final report project P 702, Forschungsvereinigung Stahlanwendung e. V. FOSTA, Düsseldorf. Yildirim, H. C., Marquis, G. B., 2012. Overview of fatigue data for high frequency mechanical impact treated welded joints, Welding in the World 56, No. 7-8, 82-96. Yildirim, H. C., 2013. Design aspects of high strength steel welded structures improved by high frequency mechanical impact (HFMI) treatment, PhD-Thesis, Aalto University, Finland. specimens. References Kern, A., Schriever, U., Hamme, U., Hauser, J., 2002a, Steel the way, Cranes today, No. 2, 54-59. Kern, A., Schriever, U., Hamme, U., Hauser, J., 2002b, Steel the way part 2, Cranes today, No. 3, 55-59.