To investigate the mechanical properties of pipeline subjected to plastic deformation, tensile tests and crack-tip-opening displacement (CTOD) tests were conducted on X60, X65, and X80 line pipe steels with uniaxial tensile or compressive prestrain, $εpr$. The tensile tests revealed that the Bauschinger effect and work hardening were dependent on the yield-to-tensile ratio $(Y∕T)$ of the steels; the change in yield stress due to prestrain linearly depended on the $Y∕T$ of the base metal. A critical CTOD for crack initiation decreased with increasing $∣εpr∣$. Compressive prestrain had a larger effect on the reduction of the critical CTOD than tensile prestrain. The test results showed that the reduction in the critical CTOD due to tensile prestrain was predictable with a simplified theoretical model employing a critical fracture strain of the base metal.

1.
Williams
,
D. N.
, 1980, “
Interaction Between the Bauschinger Effect and Strain Aging
,”
Metall. Trans. A
0360-2133,
11
, pp.
1629
1631
.
2.
Fududa
,
N.
,
Yatabe
,
H.
,
Kawaguchi
,
S.
,
Watanabe
,
T.
, and
Masuda
,
T.
, 2003, “
Experimental and Analytical Study of Cold Bending Process for Pipelines
,”
ASME J. Offshore Mech. Arct. Eng.
0892-7219,
125
, pp.
153
157
.
3.
Leis
,
B. N.
,
Goetz
,
D. P.
, and
Scott
,
P. M.
, 1986, “
Prediction of Inelastic Crack Growth in Ductile Line Pipe Materials
,” in
Proceedings of the 7th Symposium on Line Pipe Research
,
Arlington
, VA,
American Gas Association
,
16
, pp.
1
31
.
4.
Hagiwara
,
N.
,
Masuda
,
T.
, and
Oguchi
,
N.
, 2000, “
Effects of Prestrain of Fracture Toughness and Fatigue-Crack Growth of Line Pipe Steels
,”
ASME J. Pressure Vessel Technol.
0094-9930,
123
, pp.
355
361
.
5.
Cosham
,
A.
,
Palmer
,
A.
, and
Hopkins
,
P.
, 2003, “
An experimental Study of the Effect of Pre-strain on the Fracture Toughness of Line Pipe Steel
,” in
Proceedings of the 10th International Conference on Pressure Vessel Technology (ICPVT-10)
,
Vienna
, Austria, p.
357
.
6.
Cosham
,
A.
, 2001, “
A Model of Pre-Strain Effects on Fracture Toughness
,”
ASME J. Offshore Mech. Arct. Eng.
0892-7219,
123
, pp.
182
190
.
7.
Cosham
,
A.
,
Hagiwara
,
N.
,
Fukuda
,
N.
, and
Masuda
,
T.
, 2002, “
A Model to Predict the Effect of Pre-strain on the Fracture Toughness of Line Pipe Steel
,” in
Proceedings of the 4th International Pipeline Conference (IPC 2002)
,
Calgary
B
, pp.
1965
1978
.
8.
Horikawa.
,
K.
, 1980, “
Strain Aging Embrittlement of Structural Steel due to Cold Forming
,”
Proc. Japan Society of Civil Engineers
,
300
, pp.
13
20
(in Japanese).
9.
British Standard Institution (BSI
, 1991, “
Fracture Mechanics Toughness Tests—Part 1: Method for determination of KIc, Critical CTOD and Critical J Values of Metallic Materials
,” BS 7448–1.