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Research Papers: Materials and Fabrication

Evaluation of a Pipe–Flange Connection Method Based on Cold Work

[+] Author and Article Information
I. Barsoum

Department of Mechanical Engineering,
The Petroleum Institute,
P.O. Box 2533,
Abu Dhabi, UAE
e-mail: ibarsoum@pi.ac.ae

A. M. Khalaf

Department of Mechanical Engineering,
The Petroleum Institute,
P.O. Box 2533,
Abu Dhabi, UAE;
Engineering Discipline Division,
Abu Dhabi Marine Operating Company (ADMA),
P.O. Box 303,
Abu Dhabi, UAE

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received October 31, 2014; final manuscript received February 24, 2015; published online June 9, 2015. Assoc. Editor: Haofeng Chen.

J. Pressure Vessel Technol 137(6), 061407 (Dec 01, 2015) (8 pages) Paper No: PVT-14-1177; doi: 10.1115/1.4029960 History: Received October 31, 2014; Revised February 24, 2015; Online June 09, 2015

The conventional joining method of a pipe and a flange uses welding. However, welded pipe–flange joints have the drawback with the inherent distortions and residual stresses resulting from the welding process, which can affect the mechanical integrity and performance of the flange significantly. In this study, a novel pipe–flange connection method based on cold work is evaluated using the finite element method. A weld neck flange is modified by manufacturing circumferential grooves at its internal surface and the pipe is cold worked into the grooves using a hydraulic expansion tool. The finite element model incorporates a pressure dependent friction model for the contact interaction between the tool–pipe–flange and a strain-based ductile failure locus for the pipe material accounting for ductile damage initiation during the cold work process utilizing a continuum damage mechanics approach. The finite element results show that a high load carrying capacity can be achieved for the cold work pipe–flange connection and has good potential for replacing the conventional welded joint.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Cross section view of the modified welding neck flange after the expansion step

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Fig. 2

Experimental setup for tensile testing and specimen

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Fig. 3

True stress–strain behavior for SA-106 (pipe) and SA-105 (flange)

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Fig. 4

Ductile failure locus for SA-106 Gr.B

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Fig. 5

Friction coefficient μ versus dimensional stress ratio p/Sut for various strain hardening exponent values n

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Fig. 6

Assembly of the FE model

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Fig. 7

Boundary conditions and applied loads in the ¼ FE model

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Fig. 8

The three models considered

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Fig. 9

Contour plot of Mises stress after the expansion stage (model 1)

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Fig. 10

Radial force of the tool versus radial tool displacement during the expansion step

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Fig. 11

Contours of damage variable ω (Eq. (5)) during the expansion step

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Fig. 12

Axial load carrying capacity of model 1

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Fig. 13

Axial load carrying capacity of model 2

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Fig. 14

Axial load carrying capacity of model 3

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Fig. 15

Load carrying capacity of pipe–flange connection of models 1, 2, and 3 compared to the load carrying capacity of the pipe

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