Wind Energy

300 T. Ummenhofer et al.
Stress range ∆σ a [N/mm 2]
540
480
420
360
300
240
180
120
preloaded + UP
shot-peened
UP
as welded
60
104 105 106 107 Load cycles
Fig. 55.3. S–N curves of the different treated notch details
specimens based on results of other studies [1]. The results of the preloaded
and subsequently UP-treated specimens are even better than the results of
the immediate treated ones but it has to be taken into consideration that the
UP treatment has been slightly optimized. For more details see [3, 4].
55.5 Conclusions
Test results show that the application of shot peening and UP on fatigue
loaded butt welds and double bevel seams produce a high enhancement of
the fatigue strength or life time. Ultrasonic methods proved to be simply
manageable preventive or repair methods with similar beneficial effects as
shot peening, also increasing the fatigue life of preloaded notch details. It
appeared that the positive effects are based on strain hardening connected
with positive residual compressive stresses.
References
1. Manteghi S., Maddox S. J. (2004) Methods for the Fatigue Life Improvement
of Welded Joints in Medium and High Strength Steels. Proceedings of the
International Institute of Welding, IIW Dokument XIII-2006-04
2. Garf E. F. et al. (2001) Assessment of Fatigue Life of Tubular Connections
Subjected to Ultrasonic Peening Treatment. The Paton Welding Journal, Vol. 2:
12–15
3. Ummenhofer T., Weich I., Nitschke-Pagel T. (2005) Lebens- und
Restlebensdauerverlängerung geschweißter Windenergieanlagentürme und
anderer Stahlkonstruktionen durch Schweißnahtnachbehandlung. Stahlbau 74
H.8: 412–422
4. Ummenhofer T., Weich I., Nitschke-Pagel T. (2005) Extension of Life Time of
Welded Dynamic loaded Structures. IIW Document XIII-2085-05