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Research Papers: Design and Analysis

Experimental Study on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Multi-Axial Loads

[+] Author and Article Information
Yinsheng Li

Japan Atomic Energy Agency (JAEA),
Tokai-mura, Naka-gun,
Ibaraki-ken 319-1195, Japan
e-mail: li.yinsheng@jaea.go.jp

Kunio Hasegawa

Japan Atomic Energy Agency (JAEA),
Tokai-mura, Naka-gun,
Ibaraki-ken 319-1195, Japan
e-mail: kunioh@kzh.biglobe.ne.jp

Naoki Miura

Central Research Institute of Electric
Power Industry (CRIEPI),
2-6-1 Nagasaka, Yokosuka,
Kanagawa 240-0196, Japan
e-mail: miura@criepi.denken.or.jp

Katsuaki Hoshino

Electric Power Engineering Systems Co., Ltd.,
2-6-1 Nagasaka, Yokosuka,
Kanagawa 240-0196, Japan
e-mail: hoshinok@dentec.co.jp

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received January 14, 2016; final manuscript received April 22, 2016; published online August 5, 2016. Assoc. Editor: David L. Rudland.

J. Pressure Vessel Technol 139(1), 011204 (Aug 05, 2016) (10 pages) Paper No: PVT-16-1008; doi: 10.1115/1.4033531 History: Received January 14, 2016; Revised April 22, 2016

When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI (ASME Code Section XI) or JSME Rules on Fitness-for-Service for Nuclear Power Plants (JSME FFS Code) can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered. Recently, analytical investigation was carried out by the authors on the limit load of cracked pipes considering multi-axial loads including torsion. Two failure estimation methods for multi-axial loads including torsion moment with different ranges were proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads including the torsion moment and to provide experimental support for the failure estimation methods, failure experiments were performed on 20 mm diameter stainless steel pipes with a circumferential surface crack or a through-wall crack under combined axial force, bending moment, and torsion moment. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to multi-axial loads.

FIGURES IN THIS ARTICLE
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Copyright © 2017 by ASME
Topics: Stress , Torsion , Pipes , Failure
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References

Figures

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Fig. 1

Nomenclature and stress distribution for a cracked pipe subjected to bending moment

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Fig. 2

A circumferentially cracked pipe subjected to combined bending and torsion moments

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Fig. 3

Small size pipe specimen used in experiments: (a) longitudinal view of specimen and (b) crack in center section

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Fig. 4

Concept of experimental method for multi-axial loads: (a) description of experimental concept and (b) description of dimensions and loading condition

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Fig. 5

Load components in y–z and x–y planes: (a) y–z plane and (b) x–y plane

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Fig. 6

Pipe specimen with jigs for combined axial tensile, bending moment, and torsion moment (rM = 1.0): (a) general view, (b) cross section of link A, (c) specimen and link B, and (d) pipe specimen with jigs

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Fig. 7

Photograph of tensile testing apparatus

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Fig. 8

Variations of tensile load with load-line displacement: (a) a/t = 1.0 and 2θ = 90 deg, (b) a/t = 1.0 and 2θ = 120 deg, and (c) a/t = 0.5 and 2θ = 120 deg

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Fig. 9

Appearance of some failed specimens (a) ML-120-1 a/t = 1.0, 2θ = 120 deg, rM = 0.5, (b) ML-120-2 a/t = 1.0, 2θ = 120 deg, rM = 1.0, (c) ML-120-3 a/t = 1.0, 2θ = 120 deg, rM = 2.0, (d) ML-H-1 a/t = 0.5, 2θ = 120 deg, rM = 0.5, (e) ML-H-2 a/t = 0.5, 2θ = 120 deg, rM = 1.0, and (f) ML-H-3 a/t = 0.5, 2θ = 120 deg, rM = 2.0

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Fig. 10

Failure diagram showing the failure envelope and the failed specimens

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Fig. 11

Ratios of experimental failure load to predicted failure load depicted as a function of τ/σf

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Fig. 12

Ratios of experimental failure load to predicted failure load depicted as a function of τ/σf

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