Mutual interaction of stress concentration and stress intensity factor between semi-circular notch and crack

Pierre Dulieu; Valéry Lacroix; Pierre Dulieu; Valéry Lacroix

doi:10.3934/matersci.2016.4.1520

AIMS Materials Science

2016, Volume 3, Issue 4: 1520-1533. doi: 10.3934/matersci.2016.4.1520

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Mutual interaction of stress concentration and stress intensity factor between semi-circular notch and crack

Pierre Dulieu ^,,
Valéry Lacroix ^,

Tractebel (ENGIE), Avenue Ariane 7, 1200 Brussels, Belgium

Received: 21 September 2016 Accepted: 06 November 2016 Published: 14 November 2016

When cracks are detected during examination, assessments have to be done in order to demonstrate the fitness-for-service (FFS) of the component for continued operation. In order to assess a crack, it has firstly to be characterized as surface or subsurface according to its distance to the free surface of the component. The re-characterization process from subsurface-to-surface crack is addressed in all FFS Codes. The specific criteria for the rules on transforming subsurface cracks to surface cracks differ among the FFS Codes and assume regular free surface of the component. In this article, in order to further improve the subsurface-to-surface flaw proximity rules, a new parameter is investigated: the presence of a geometrical discontinuity at the free surface of the component. The analysis, conducted through extended finite element calculations, considered the interaction between a circular subsurface crack and the free surface with stress concentration induced by a circular notch. After analyzing the stress profiles in the notch-crack neighborhood, the calculations have highlighted that, for a given stress concentration at the free surface of the component, for a given ligament and for a given crack depth, the interaction between the crack and the notch highly depends on the notch radius. These results lead to the proposal of a new subsurface-to-surface proximity rule accounting for the interaction between circular crack and the free surface of the component impacted by a stress concentration due to a circular notch.
- crack interaction,
- flaw characterization,
- fracture mechanics,
- stress intensity factor,
- stress concentration,
- extended finite element method
Citation: Pierre Dulieu, Valéry Lacroix. Mutual interaction of stress concentration and stress intensity factor between semi-circular notch and crack[J]. AIMS Materials Science, 2016, 3(4): 1520-1533. doi: 10.3934/matersci.2016.4.1520

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Abstract

When cracks are detected during examination, assessments have to be done in order to demonstrate the fitness-for-service (FFS) of the component for continued operation. In order to assess a crack, it has firstly to be characterized as surface or subsurface according to its distance to the free surface of the component. The re-characterization process from subsurface-to-surface crack is addressed in all FFS Codes. The specific criteria for the rules on transforming subsurface cracks to surface cracks differ among the FFS Codes and assume regular free surface of the component. In this article, in order to further improve the subsurface-to-surface flaw proximity rules, a new parameter is investigated: the presence of a geometrical discontinuity at the free surface of the component. The analysis, conducted through extended finite element calculations, considered the interaction between a circular subsurface crack and the free surface with stress concentration induced by a circular notch. After analyzing the stress profiles in the notch-crack neighborhood, the calculations have highlighted that, for a given stress concentration at the free surface of the component, for a given ligament and for a given crack depth, the interaction between the crack and the notch highly depends on the notch radius. These results lead to the proposal of a new subsurface-to-surface proximity rule accounting for the interaction between circular crack and the free surface of the component impacted by a stress concentration due to a circular notch.

References

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