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Research Papers: Design and Analysis

Stress Intensity Factor and Elastic Crack Opening Displacement Solutions of Complex Cracks in Pipe Using Elastic Finite-Element Analyses

[+] Author and Article Information
Jae-Uk Jeong, Jae-Boong Choi

School of Mechanical Engineering,
Sungkyunkwan University,
2066 Seobu-ro, Jangan-gu,
Suwon, Gyeonggi-do 440-746, South Korea

Nam-Su Huh

Department of Mechanical System
Design Engineering,
Seoul National University of
Science and Technology,
232 Gongneung-ro, Nowon-gu,
Seoul 139-743, South Korea
e-mail: nam-su.huh@seoultech.ac.kr

Yun-Jae Kim

Department of Mechanical Engineering,
Korea University,
145 Anam-ro, Seongbuk-gu,
Seoul 136-713, South Korea

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received March 22, 2015; final manuscript received June 24, 2015; published online September 7, 2015. Assoc. Editor: Haofeng Chen.

J. Pressure Vessel Technol 138(1), 011206 (Sep 07, 2015) (11 pages) Paper No: PVT-15-1048; doi: 10.1115/1.4031128 History: Received March 22, 2015; Revised June 24, 2015

In the present paper, the closed-form expressions for the stress intensity factors (SIFs) and the elastic crack opening displacements (CODs) of complex-cracked pipes are derived based on the systematic three-dimensional (3D) elastic finite-element (FE) analyses. The loading conditions that are evaluated include global bending moment, axial tension, and internal pressure. In terms of geometries, the geometric variables affecting the SIFs and the elastic CODs of complex-cracked pipes, i.e., the crack angle of through-wall cracks (TWCs), the crack depth of fully circumferential, internal surface cracks in the inner surface of pipe, and the ratio of pipe mean radius to thickness, are systematically considered in the present FE analyses. The FE analysis procedure employed in the present study has been validated against the existing solutions for the circumferential TWC pipes. Using the present FE results, the shape factors of SIF and elastic COD for complex-cracked pipes are tabulated as a function of geometric variables. The results are applied for closed-form expressions of SIF and elastic COD when the pipe is subjected to simple loading conditions of bending, axial tension, or internal pressure. The proposed closed-form expressions can estimate SIF and elastic COD of complex-cracked pipes within maximum differences of 2.4% and 5.9% with FE results, respectively.

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References

Figures

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Fig. 3

Typical FE mesh of a pipe with a complex crack employed in the present study

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Fig. 5

Distributions of SIF along the crack front of complex crack

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Fig. 6

The points along the crack front to calculate the SIFs of a complex crack

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Fig. 7

The points for the elastic CODs of a complex-crack

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Fig. 8

Comparisons of the shape factors from the existing solution with the present FE results for TWC in pipe under bending moment

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Fig. 2

Schematics of pipes with a complex crack under global bending moment, axial tension, and internal pressure

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Fig. 1

Geometries of a complex crack in pipes [4]

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Fig. 4

Crack face pressures on a complex crack employed in the present FE study

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Fig. 12

Comparisons of the SIFs and the elastic CODs between the results from the proposed solutions (Eqs. (13) and (14)) and the reduced thickness analogy for complex-cracked pipe under bending moment (a/t = 0.5)

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Fig. 9

Comparisons of the shape factors for the SIFs from the present FE results (Table 2) with the proposed closed-form solution (Eq. (13)) for complex-cracked pipe under bending moment

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Fig. 10

Comparisons of the shape factors for the elastic CODs from the present FE results (Table 9) with the proposed closed-form solution (Eq. (14)) for complex-cracked pipe under axial tension

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Fig. 11

Generic idea of reduced thickness analogy for a complex-cracked pipe

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