Estimation of Endurance Limit under Multiaxial LoadingMultiaxial criteria for endurance limit prediction of metallic materials will be discussed in this paper.The Shear Stress Intensity Hypothesis SIH is improved under consideration of the variable fatigue limit ratio zwlow and mean stress effects. Fatigue behaviour under synchronous and nonsynchronous stresses and influences such as mean stresses, out-of-phase stresses, different frequencies, nonsinusoidal stress time function are analysed theoretically and verified with test results. The prediction according to SIH shows good agreement with the test results. Based on an extensive statistical investigation it can be recommended to use the SIH for "crack free materials" and the normal stress hypothesis NSH for "materials with cracks".For components the hypothesis SIH and NSH are developed under consideration of the notch effect. In this study a concept for the prediction of endurance limit under multiaxial loads has been developed.

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zum 65. Geburtstag gewidmet Im vorliegenden Beitrag wird ein Modell zur Dauerfestigkeitsberechnung in [ 111 auf den Zeitfestigkeitsbereich erweitert. Beriicksichtigt werden der statistische GrGDeneinfluB nach dem Fchlstellenmodell und die spannungsmechanische Stutzwirkung infolge der plastischen Verformung im Kerbgrund. Das vorgestellte Modell wird fur die Grenzfalle besonders analysiert und rnit Versuchsergebnisscn aus der Literatur verifiziert. Nach dem vorgestellten Modell ist die Neigung dcr Wohlerlinie von der Wechselfestigkcit des Werkstoffes und von der KerbgrundgrGRe abhangig und unabhangig von der Formzahl. Die Wijhlerlinie wird desto flacher, je grol3er die KerbgrundgrGRe ist und j e hoherfester der Werkstoff ist.In this paper a concept for the estimation of fatigue limit in [11] will be extended to the calculation of S-N-curves. The statistical size effect is taken into account with the well known weakest link theory. The geometrical size effect is considered according to the cyclic plastic deformation in the notch root.This model gives good correlation with test results.According to the present model the slope of the S-N curve depends on the specimen size and strcngth of materials, but does not depend on the stress concentration factor. The S-N-curve becomes flatter with larger notch size and higher material strength.