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Research Papers: Design and Analysis

Plastic Load of Precracked Polyethylene Miter Pipe Bends Subjected to In-Plane Bending Moment1

[+] Author and Article Information
Tarek M. A. A. EL-Bagory

Assistant Professor
Department of Mechanical Engineering,
College of Engineering,
Majmaah University, KSA,
Majmaah, Riyadh 11952, Saudi Arabia
e-mail: telbagory@yahoo.com

Maher Y. A. Younan

Associate Dean, School of Sciences
and Engineering,
Department of Mechanical Engineering,
The American University in Cairo AUC,
Cairo 11835, Egypt
e-mail: myounan@aucegypt.edu

Hossam E. M. Sallam

Professor in Civil Engineering Department,
Faculty of Engineering,
Jazan University, KSA,
Jazan 82822-6694, Saudi Arabia
e-mail: hem_sallam@yahoo.com

Lotfi A. Abdel-Latif

Professor
Department of Mechanical Design,
Faculty of Engineering, El-Mataria
Helwan University,
Cairo, El-Mataria 11724, Egypt
e-mail: lotlatif2012@gmail.com

Department of Mechanical Design, Faculty of Engineering, Mataria, Helwan University, Cairo, Egypt Participated in the Euro-Mediterranean Innovation Marketplace 26th–28th January, 2010, Cairo, Egypt, “Ranked as the first among all the applicants of the contest” for the Invention “Testing Station for Natural Gas Piping Systems.”

Pipes & Plastic Products Company (PPP) in the 10th of Ramadan City, Egypt.

1Participated in the Proceedings of the ASME 2010 Pressure Vessels & Piping Division/K-PVP Conference PVP2010, July 18–22, 2010, Bellevue, WA, USA, Paper No. PVP 2010-25397.

2Participated in the Euro-Mediterranean Innovation Marketplace 26th–28th January, 2010, Cairo, Egypt, “Ranked as the first among all the applicants of the contest,” for the Invention “Testing Station for Natural Gas Piping Systems.”

3On sabbatical leave from Helwan University, Department of Mechanical Design, Faculty of Engineering, El-Mataria Helwan University, Cairo, El-Mataria, 11724, Egypt.

4On sabbatical leave from Zagazig University, Department of Materials Engineering, Faculty of Engineering, Zagazig, 44519, Egypt.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the Journal of Pressure Vessel Technology. Manuscript received August 19, 2010; final manuscript received August 16, 2012; published online October 7, 2013. Assoc. Editor: Donald Mackenzie.

J. Pressure Vessel Technol 135(6), 061203 (Oct 07, 2013) (9 pages) Paper No: PVT-10-1129; doi: 10.1115/1.4024658 History: Received August 19, 2010; Revised August 16, 2012

The main purpose of the present paper is to investigate the effect of crack depth on the plastic load (collapse load) of miter pipe bends (MPB) under in-plane bending moment. The experimental work is conducted to investigate multimiter pipe bends, with a bend angle 90 deg, pipe bend factor h = 0.844, standard dimension ratio (SDR) = 11, and number of welding junctions m = 3 under a crosshead speed 500 mm/min. The material of the investigated pipe is a high-density polyethylene (HDPE), which is used in natural gas (NG) piping systems. The welds in the miter pipe bends are produced by butt-fusion method. The crack depth varies from intrados to extrados location according to the in-plane opening/closing bending moment, respectively. For each in-plane bending moment, the plastic load is obtained by the tangent intersection (TI) method from the load–deflection curves produced by the testing machine specially designed and constructed in the laboratory.5 The study reveals that increasing the crack depth leads to a decrease in the stiffness and plastic load of MPB for both in-plane closing and opening bending moment. Higher values of the plastic load are reached in case of opening bending moment. This behavior is true for all investigated crack depths. A circumferential external crack has an obvious effect on the behavior of load–deflection curve. The linear elastic region in both mode of loading decreases with increasing crack depth.

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Figures

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Fig. 1

Smooth pipe bend (elbow)

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Fig. 2

Schematic illustration of (a) miter pipe bend with attached straight pipe and (b) coordinates of load sign

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Fig. 3

Crack geometry and razor blade configurations

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Fig. 4

Schematic illustration of test rig

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Fig. 5

Collapse load construction by TI method [47]

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Fig. 6

Load–deflection curves for in-plane bending (−Fy) at a/W = 0

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Fig. 7

Load–deflection curves for in-plane bending (−Fy) at a/W = 0.1

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Fig. 8

Load–deflection curves at load line (δ0) for in-plane bending (−Fy) at different crack depths

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Fig. 9

Trend of variation in collapse load with crack width ratio, a/W for in-plane closing (−Fy)

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Fig. 10

Load–deflection curves for in-plane bending (+Fy) at a/W = 0

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Fig. 11

Load–deflection curves at the load line (δ0) for the case in-plane open (+Fy) at different crack depths

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Fig. 12

Variation of collapse load with crack width ratio for in-plane opening (+Fy)

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Fig. 13

Load–deflection curves at load line (δ0), and different a/W for in-plane close and open loading

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Fig. 14

Variation of collapse load with crack width ratio for in-plane open and close

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Fig. 15

Variation of collapse load ratio with crack width ratio for in-plane open and close

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