Research article Special Issues

Effect of interaction of embedded crack and free surface on remaining fatigue life

  • Received: 29 September 2016 Accepted: 23 November 2016 Published: 05 December 2016
  • Embedded crack located near free surface of a component interacts with the free surface. When the distance between the free surface and the embedded crack is short, stress at the crack tip ligament is higher than that at the other area of the cracked section. It can be easily expected that fatigue crack growth is fast, when the embedded crack locates near the free surface. To avoid catastrophic failures caused by fast fatigue crack growth at the crack tip ligament, fitness-for-service (FFS) codes provide crack-to-surface proximity rules. The proximity rules are used to determine whether the cracks should be treated as embedded cracks as-is, or transformed to surface cracks. Although the concepts of the proximity rules are the same, the specific criteria and the rules to transform embedded cracks into surface cracks differ amongst FFS codes. This paper focuses on the interaction between an embedded crack and a free surface of a component as well as on its effects on the remaining fatigue lives of embedded cracks using the proximity rules provided by the FFS codes. It is shown that the remaining fatigue lives for the embedded cracks strongly depend on the crack aspect ratio and location from the component free surface. In addition, it can be said that the proximity criteria defined by the API and RSE-M codes give overly conservative remaining lives. On the contrary, the WES and AME codes always give long remaining lives and non-conservative estimations. When the crack aspect ratio is small, ASME code gives non-conservative estimation.

    Citation: Genshichiro Katsumata, Valéry Lacroix, Yinsheng Li. Effect of interaction of embedded crack and free surface on remaining fatigue life[J]. AIMS Materials Science, 2016, 3(4): 1748-1758. doi: 10.3934/matersci.2016.4.1748

    Related Papers:

  • Embedded crack located near free surface of a component interacts with the free surface. When the distance between the free surface and the embedded crack is short, stress at the crack tip ligament is higher than that at the other area of the cracked section. It can be easily expected that fatigue crack growth is fast, when the embedded crack locates near the free surface. To avoid catastrophic failures caused by fast fatigue crack growth at the crack tip ligament, fitness-for-service (FFS) codes provide crack-to-surface proximity rules. The proximity rules are used to determine whether the cracks should be treated as embedded cracks as-is, or transformed to surface cracks. Although the concepts of the proximity rules are the same, the specific criteria and the rules to transform embedded cracks into surface cracks differ amongst FFS codes. This paper focuses on the interaction between an embedded crack and a free surface of a component as well as on its effects on the remaining fatigue lives of embedded cracks using the proximity rules provided by the FFS codes. It is shown that the remaining fatigue lives for the embedded cracks strongly depend on the crack aspect ratio and location from the component free surface. In addition, it can be said that the proximity criteria defined by the API and RSE-M codes give overly conservative remaining lives. On the contrary, the WES and AME codes always give long remaining lives and non-conservative estimations. When the crack aspect ratio is small, ASME code gives non-conservative estimation.


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    [1] Hasegawa K, Bezensek B, Scarth DA (2016) Global Harmonization of Flaw Modeling/Characterization. Global Applications of the ASME Boiler & Pressure Vessel Code, ASME Press.
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    [9] Association of Mechanical Engineers, Section IV (2008) Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs (VERLIFE).
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    [11] Miyazaki K, Iwamatsu F, Nakanishi S, et al. (2006) Stress Intensity Factor Solution for Subsurface Flaw Estimated by Influence Function Method. ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference, Vancouver, Canada.
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  • © 2016 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)
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