Verallgemeinerte Berücksichtigung der Dauerfestigkeit im Ermüdungsfestigkeitsnachweis mittels Lebensdauerlinien

Generalized consideration of endurance limit for fatigue stress analysis by means of fatigue life curves.

The S-N curve in the original form applies for constant amplitude loading. For fatigue assessment by damage accumulation theory under the most likely variable amplitude loading, several approaches exist to account for the endurance limit. The design S-N curve with two knee points used in Eurocode 3 is one of these approaches. By means of implementing the fatigue life curves, a well-known concept in mechanical engineering, a generalized consideration of different, even nonlinear approaches of endurance limit is possible for fatigue life assessment.
Considering a nonlinear endurance limit for variable amplitude loadings is to date not included in the codes and guidelines for design and assessment of new and existing structures, respectively. It has a considerable economical significance, though: An increase of the calculated fatigue life by 10 times is by no means improbable.
In this article, the calculation and evaluation of fatigue life curves are represented. These are dependent on the shape of the stress range spectrum, the total number of stress cycles as well as the approach for considering the endurance limit. Calculations via fatigue life curves are demonstrated using examples of offshore wind turbines and an existing highway bridge.