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Research Papers: Design and Analysis

Nonidealized Surface to Through-Wall Crack Transition Model for Axial Cracks in Cylinders

[+] Author and Article Information
Do-Jun Shim

Engineering Mechanics Corporation of Columbus,
3518 Riverside Drive, Suite 202,
Columbus, OH 43221
e-mail: djshim@emc-sq.com

Jeong-Soon Park

Korea Institute of Nuclear Safety,
62 Gwahak-ro, Yuseong-gu,
Daejeon 305-338, South Korea

David Rudland

Office of Nuclear Regulatory Research,
U.S. Nuclear Regulatory Commission,
Mail Stop: CSB-5CA24,
Washington, DC 20555-000

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received January 30, 2015; final manuscript received May 6, 2015; published online August 25, 2015. Assoc. Editor: Wolf Reinhardt.This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Pressure Vessel Technol 138(1), 011203 (Aug 25, 2015) (7 pages) Paper No: PVT-15-1017; doi: 10.1115/1.4030625 History: Received January 30, 2015

Recent studies have shown that a subcritical surface crack, due to primary water stress corrosion cracking (PWSCC), can transition to a through-wall crack (TWC) with significant differences between the inner diameter (ID) and outer diameter (OD) crack lengths. This behavior has been observed for both circumferential and axial cracks. Recently, a surface to TWC transition model has been developed for circumferential cracks using existing K and COD (crack opening displacement) solutions for nonidealized circumferential TWCs. In this paper, a similar crack transition model (CTM) was developed for axial cracks. As a first step, a study was conducted to define the appropriate crack front shape for nonidealized axial TWCs. Then, elastic finite element analyses were carried out to develop K and COD solutions using these crack front shapes. The newly developed solutions were utilized for the CTM. The present CTM includes a criterion for transitioning the final surface crack to the initial nonidealized TWC. This criterion determines when the transition should occur (based on surface crack depth) and determines the two crack lengths (at ID and OD surfaces) of the initial nonidealized TWC. Furthermore, nonidealized TWC growth calculation can be conducted using the proposed model. Example results (crack length and COD) obtained from the proposed model were compared to those obtained from the natural crack growth simulations. Results presented in this paper demonstrated the applicability of the proposed model for simulating axial crack transition.

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References

Figures

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Fig. 1

Shape of nonidealized axial TWC assumed in Ref. [6]

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Fig. 2

Example FE mesh of nonidealized axial TWC obtained during natural crack growth

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Fig. 3

AFEA results showing the natural crack front shapes obtained during crack transition

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Fig. 4

Crack lengths at ID and OD surfaces as a function of time

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Fig. 5

Centerline COD values at ID and OD surfaces as a function of time

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Fig. 6

Comparison of crack front shape (a) and K values (b) between straight and natural crack

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Fig. 7

Representation of natural crack front shape using part of an ellipse for (a) crack shapes at early stage of crack transition and (b) for the entire crack transition

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Fig. 8

Variation of shape functions (a) F and (b) V1 and V2 for idealized axial TWC under internal pressure

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Fig. 9

Variation of correction factors (G1 and G2) for nonidealized axial TWC under internal pressure (Rm/t = 5)

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Fig. 10

Variation of correction factors (a) H1 and (b) H2 for nonidealized axial TWC under internal pressure (Rm/t = 5)

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Fig. 11

Illustration of crack transition from surface crack to initial nonidealized TWC

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Fig. 12

Idealized TWC (dashed line) used for calculation of K and COD for nonidealized TWC

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Fig. 13

Crack growth calculation using K values at ID and OD surface points of nonidealized TWC

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Fig. 14

Comparison of half-crack length obtained from natural crack growth (AFEA) and CTM

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Fig. 15

Comparison of COD obtained from natural crack growth (AFEA) and CTM

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