0
RESEARCH PAPERS

A Failure Assessment Method for a Pipe Bend Subjected to Both a Bending Moment and Internal Pressure

[+] Author and Article Information
Masaki Yoshikawa

 JFE R&D Corporation, 1-1, Minamiwatarida, Kawasaki-ku, Kawasaki, 210-0855 Japanm-yoshikawa@jfe-rd.co.jp

Akihiko Katoh

 JFE R&D Corporation, 1-1, Minamiwatarida, Kawasaki-ku, Kawasaki, 210-0855 Japana-kato@jfe-rd.co.jp

Kazuaki Sasaki

Faculty and Graduate School of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, 060-8628 Japankazki@eng.hokudai.ac.jp

J. Pressure Vessel Technol 128(4), 605-617 (Dec 01, 2005) (13 pages) doi:10.1115/1.2349574 History: Received June 12, 2005; Revised December 01, 2005

This paper proposes a new failure assessment method for a steel pipe bend subjected to both a bending moment and internal pressure. Consistent with previous studies, it was shown that the maximum bending moment of a pipe bend subjected to a bending moment increases with the addition of internal pressure. However, it was experimentally confirmed that the addition of this internal pressure has the detrimental effect of significantly reducing the critical deformation (maximum bending angle) of the pipe bend. In addition, it was found that, subsequent to the application of a large deflection, cracks initiate at the most deformed part of the pipe bend during the process of unloading the internal pressure and then the applied load. Herein, the authors propose a practical failure assessment method which uses small-scale tests and nonlinear finite element (FE) analyses to predict the critical deformation and crack initiation position for a full-scale pipe bend. The failure criterion, which uses principal stress, mean stress, and equivalent plastic strain, was developed using small-scale tests. A failure assessment was conducted by comparing the predictions of this criterion with stress and strain histories obtained from FE analyses. Also, the authors’ failure criterion was compared with previous failure criteria, and the advantages/disadvantages discussed.

Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Schematic figure of the pipe specimen

Grahic Jump Location
Figure 2

Outline of the full-scale pipe bend experiment: (a) front view of a pipe specimen in situ, (b) side view of a pipe specimen in situ, and (c) schematic of the loading procedure

Grahic Jump Location
Figure 3

Approximation method for the stress-strain curve of the steel pipe material (material A)

Grahic Jump Location
Figure 4

Example of the mesh division used in the FE analysis of specimen No.1

Grahic Jump Location
Figure 5

Crack initiation region of the failed specimens after the full-scale pipe bend experiments

Grahic Jump Location
Figure 6

Relationship between bending moment and bending angle for pipe specimens Nos. 1 and 3

Grahic Jump Location
Figure 7

The appearance of pipe specimen No. 3 after the full-scale pipe experiment: (a) front view of the bent specimen, (b) cracks observed by a color check of the intrados side of the pipe bend, and (c) crack in the flank side of the pipe bend

Grahic Jump Location
Figure 8

Comparison between the experimentally measured maximum moment and that predicted from the FE analyses

Grahic Jump Location
Figure 9

Comparison between the experimentally measured strain distribution at the center section of the pipe bend for specimen No. 3 and that predicted from the FE analysis: L-d and C-d denote the longitudinal and circumferential directions, respectively

Grahic Jump Location
Figure 10

Comparison between the experimentally measured maximum compressive strain history in the longitudinal direction at the center section of the pipe bend for specimens Nos. 1 and 3 and that predicted from the FE analysis

Grahic Jump Location
Figure 11

Comparison of the longitudinal stress distribution at the center section before and after unloading: (a) specimen No. 1, (b) specimen No. 3; B.U. and E.U. denote the beginning of unloading and the end of unloading, respectively

Grahic Jump Location
Figure 12

Comparison of the equivalent plastic strain distribution at the center section before each unloading: (a) specimen No. 1, (b) specimen No. 3; B.U. denotes the beginning of unloading

Grahic Jump Location
Figure 13

Peak values of principal stress ratio and equivalent plastic strain at the end of the final unloading as predicted from the FE analyses: (a) principal stress ratio and (b) equivalent plastic strain

Grahic Jump Location
Figure 14

Representation of the developed failure assessment surfaces of the authors’ failure criterion

Grahic Jump Location
Figure 15

Geometry and size of the notched round bar tensile specimen

Grahic Jump Location
Figure 16

Appearance of the Sp1 type notched round bar tensile specimen for material A: (a) before test and (b) after test

Grahic Jump Location
Figure 17

Stress and strain at the minimum cross section of the notched specimen

Grahic Jump Location
Figure 18

Relationship between the average longitudinal stress and the equivalent plastic strain at the minimum cross section of the notched specimens for material A

Grahic Jump Location
Figure 19

Relationship between the mean stress ratio and equivalent plastic strain at failure

Grahic Jump Location
Figure 20

Failure assessment surfaces of the authors’ failure criterion

Grahic Jump Location
Figure 21

Comparison of the failure assessment results for Eq. 10 and the results of the FE analyses: (a) material A, (b) material B, and (c) material C

Grahic Jump Location
Figure 22

Example comparison of the failure assessment results of Eq. 11 and the results of the FE analyses: (a) No. 1, (c) No. 10, and (e) No. 13 are nonfailed specimens; (b) No. 3, (d) No. 11, and (f) No. 17 are the failed specimens. The “dotted” circle identifies the crack initiation position

Grahic Jump Location
Figure 23

History of longitudinal stress ratio (σ1∕σu)FEM∕(σ1∕σu)cr for specimens Nos. 1 and 3

Grahic Jump Location
Figure 24

Comparison of failure assessment results: (a) Norris, (b) Tai, and (c) authors’ criterion

Grahic Jump Location
Figure 25

Equilibrium of forces in the notch region

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In