Conclusions
-
1.
The notch sensitivity of structural steels increases (practically linearly) when the proportion of high-strength structural components (sorbite and pearlite) in their structure increases; this is determined by their suitability for more intense piling up of dislocations at obstacles.
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2.
The greater notch sensitivity of the high-strength structural components is the reason why the fatigue limit of specimens with stress raiser increases less with increasing tensile strength than the fatigue limit of smooth specimens, and from some value of σu onward it remains practically unchanged (and in isolated cases even decreases). The use of high-strength steel, especially temper hardened one, is therefore not always expedient.
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3.
The rate of increase of the fatigue limit of specimens due to increased σu slows down when the stress concentration increases and also under the effect of the scale factor.
-
4.
For making parts subjected to fatigue in operation, it is best to use steels with high static strength and to apply surface plastic strain (SPS) to them. The effectiveness of strengthening by SPS increases with increasing σu of the steels.
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Additional information
Kramatorsk Industrial Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 34–39, January, 1989.
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Belkin, A.M., Belkin, M.Y., Vishnevskii, A.P. et al. Notch sensitivity of structural steels in different structural states. Met Sci Heat Treat 31, 42–49 (1989). https://doi.org/10.1007/BF00735328
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DOI: https://doi.org/10.1007/BF00735328