Cold bends are frequently required in energy pipelines in order to change the vertical and horizontal orientations of the pipeline route. They are produced by plastically bending a pipe joint in a cold bending machine by creating a series of uniformly spaced incremental bends. This procedure acts to reduce the moment capacity and buckling strain of the pipe, and studying the changes in pipe properties caused by cold bending is valuable in assessing the level of this strength reduction. Accordingly, the initial imperfections and material transformations of five full-scale cold bend pipes were assessed in this research program. The imperfections were measured at several locations around the circumference of the specimens, along the entire bend length. It was determined that the distribution of imperfections was similar in shape to a sine function, and their amplitude ranged from $0.3mmto1.0mm$. Tension coupon tests were conducted on the intrados, extrados, and virgin materials of the specimens. It was revealed that the extrados material exhibited an increase in yield strength due to work hardening and that the intrados material demonstrated a reduction in yield strength due to the Bauschinger effect. It was established that the imperfections, and material transformations in the specimens were predominantly unaffected by the incremental-bend magnitude or spacing that was employed during the cold bending procedure.

1.
Rosenfeld
,
M. J.
,
Hart
,
J. D.
,
Zulfiqar
,
N.
, and
Gailing
,
R. W.
, 2002, “
Development of Acceptance Criteria for Mild Ripples in Pipeline Field Bends
,”
Proceedings of the IPC2002 Fourth International Pipeline Conference
,
American Society of Mechanical Engineers
,
Calgary, Alberta
.
2.
DNV-OS-F101, 2000, “
Offshore Standard OS-F101, Submarine Pipeline Systems
,”
Det Norske Veritas
, Hovik, Norway.
3.
,
N.
,
Yatabe
,
H.
,
Watanabe
,
T.
,
Kawaguchi
,
S.
, and
Masuda
,
T.
, 2001, “
Experimental and Analytical Study of Cold Bending Process for Pipelines
,”
Proceedings of the OMAE’01 20th International Conference on Offshore Mechanics and Arctic Engineering
,
American Society of Mechanical Engineers
,
Rio de Janeiro, Brazil
.
4.
American Society for Testing and Materials, 1994, “
Standard Test Methods and Definitions for Mechanical Testing of Steel Products
,” ASTM Designation No. A370–94.
5.
Callister
,
W. D.
, 1994,
Materials Science and Engineering: An Introduction
, 3rd ed.,
Wiley
,
New York
.
6.
Murray
,
N. W.
, and
Bilston
,
P.
, 1992, “
Elasto-Plastic and Strain-Hardening Bending of Thin Steel Pipes in the Pre-Buckling Region
,” Transactions of the Institution of Engineers,
Australia Civil Engineering
,
CE34
(
3
), September 1992, pp.
247
253
.
7.
Abel
,
A.
, 1987, “
Historical Perspectives and Some of the Main Features of the Bauschinger Effect
,”
Material Forum
,
Institution of Engineers
,
Australia
, Vol.
10
, pp.
11
26
.
8.
Bilston
,
P.
, and
Murray
,
N.
, 1993, “
The Role of Cold Field Bending in Pipeline Construction
,”
Eighth Symposium on Line Pipe Research
,
American Gas Association
, Paper No. 27.
9.
Z662–03 Oil and Gas Pipeline Systems
,” Canadian Standards Association, Etobicoke, Ontario.
10.
Dorey
,
A. B.
,
Cheng
,
J. J. R.
, and
Murray
,
D. W.
, 2001, “
Critical Buckling Strains for Energy Pipelines
,” Department of Civil Engineering,
University of Alberta
, Structural Engineering Report No. 237.
11.
,
N.
,
Yatabe
,
H.
,
Masuda
,
T.
, and
Toyoda
,
M.
, 2002, “
Effect of Changes in Tensile Properties Due to Cold Bending on Large Deformation Behaviour of High-Grade Cold Bend Pipe
,”
Proceedings of the IPC2002 Fourth International Pipeline Conference
,
American Society of Mechanical Engineers
,
Calgary, Alberta
.
12.
Sen
,
M.
,
Cheng
,
J. J. R.
,
Murray
,
D. W.
,
Zhou
,
Z.
,
,
K.
,
Yoshizaki
,
K.
,
,
N.
,
Como
,
M.
, and
Cerelli
,
E.
, 2004, “
Full Scale Tests of Cold Bend Pipes
,”
Proceedings of the Fifth Biennial International Pipeline Conference
,
American Society of Mechanical Engineers
,
Calgary, Alberta
, pp.
419
426
.
13.
Sen
,
M.
,
Cheng
,
J. J. R.
, and
Murray
,
D. W.
, 2005, “
Behavior of Cold Bend Pipes Under Combined Loads
,” Department of Civil Engineering, University of Alberta, Pipeline Technology Report.
14.
Yoshizaki
,
K.
, and