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Research Papers: Materials and Fabrication

Fatigue Crack Propagation Analysis of Repaired Pipes With Composite Patch Under Cyclic Pressure

[+] Author and Article Information
Mir Ali Ghaffari

Department of Mechanical and Industrial Engineering and Center for Computer-Aided Design,
The University of Iowa,
Iowa City, IA 52242
e-mail: ali-ghaffari@uiowa.edu

Hossein Hosseini-Toudeshky

Professor
Fatigue and Fracture Laboratory,
Amirkabir University of Technology,
Tehran, Iran
e-mail: hosseini@aut.ac.ir

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the Journal of Pressure Vessel Technology. Manuscript received November 21, 2012; final manuscript received February 1, 2013; published online May 21, 2013. Assoc. Editor: Saeid Mokhatab.

J. Pressure Vessel Technol 135(3), 031402 (May 21, 2013) (9 pages) Paper No: PVT-12-1173; doi: 10.1115/1.4023568 History: Received November 21, 2012; Revised February 01, 2013

The pipes in offshore and marine structures are mainly made of low-strength structural steels such as A537 steel and are subjected to the effects of both corrosive medium and cyclic loading caused by many factors. Reinforcement and repair of components using composite patches can be used for piping to reduce the stress intensity factors at the crack-front of a corrosion fatigue crack. In this paper 3D finite element analyses in general mixed-mode fracture condition are performed to study the crack growth behavior of repaired pipes subjected to internal cyclic pressure. The required formulations, crack growth modeling, and remeshing are automatically handled by developing an ANSYS parametric design language (APDL) program. For this purpose an offshore pipe made of low-strength steel containing an initial fatigue corrosion crack repaired by glass/epoxy composite patch is considered. A parametric study will be performed to find the effects of patch thickness on fatigue crack growth life extension and crack-front shape of the repaired pipes.

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References

Figures

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Fig. 5

(a) Half section of cracked pipe repaired by composite patch lay-up of [90]4 that clearly shows crack trajectory and crack front shape; (b) fatigue crack-front evolution and type of meshing for repaired pipes with patch lay-up of [90]2

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Fig. 4

Typical FEM mesh, (a) distribution of elements along the thickness, (b) overall meshing from outside view

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Fig. 3

Fatigue crack growth rates for A537 steel in various temperatures [32]

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Fig. 11

Comparison of the obtained crack-front shapes at XCtip = 90 mm for repaired pipes with various patch thickness and unrepaired pipe

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Fig. 12

Deformed repaired pipe under internal pressure

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Fig. 2

(a) Modified crack closer technique for an eight nodes solid element; (b) crack deflection angles φ0 and ψ0 for a general mixed-mode condition [35]

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Fig. 1

Typical geometry and loading of a repaired pipes

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Fig. 6

Comparison between the predicted crack growth behaviors with experimental results of Ref. [34]; (a) unrepaired panel, (b) results at unpatched surface of repaired panel with patch lay-up of [105]4

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Fig. 7

Variation of stress intensity factors along the initial crack-front (Δa = 0) for various patch layers, (a) KI, (b) KII, and(c) KIII

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Fig. 8

Variation of KI versus half of the crack length (Xctip), (a) [90]2 patch and (b) [90]16 patch

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Fig. 9

Predicted crack growth versus number of cycles for repaired pipes with various patch thickness

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Fig. 10

Crack-front development for repaired pipes with various patch lay-ups in X-Z plane; (a) [90]4, (b) [90]16

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