Effect of Prestrain on Tensile and Fracture Toughness Properties of Line Pipes

2005 ◽  
Vol 127 (3) ◽  
pp. 263-268 ◽  
Author(s):  
Naoki Fukuda ◽  
Naoto Hagiwara ◽  
Tomoki Masuda
Keyword(s):  
Base Metal ◽  
Bauschinger Effect ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Line Pipe ◽  
Critical Fracture ◽  
Crack Tip Opening

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.

Effect of Prestrain on Tensile and Fracture Toughness Properties of Line Pipes

2002 ◽  
Author(s):  
Naoki Fukuda ◽  
Naoto Hagiwara ◽  
Tomoki Masuda
Keyword(s):  
Base Metal ◽  
Bauschinger Effect ◽  
Fracture Strain ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Line Pipe ◽  
Critical Fracture ◽  
Crack Tip Opening

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 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.

Experimental Research on Fracture Toughness of High Grade Line Pipe

2012 ◽  
Vol 525-526 ◽  
pp. 425-428
Author(s):  
Qing Ren Xiong ◽  
Jian Xun Zhang ◽  
Yao Rong Feng ◽  
Hai Tao Wang ◽  
Qiu Rong Ma ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Test Results ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Line Pipe ◽  
Propagation Resistance ◽  
Crack Propagation Resistance ◽  
Initiation And Propagation ◽  
Point Bend ◽  
Crack Tip Opening

Crack tip opening displacement (CTOD) tests were carried out on different positions of X70, X80 and X100 pipe by three-point bend testing method. The results show that the crack propagation resistance and the tear modulus of base metal, heat affected zone (HAZ), and weld of X70 and X80 pipe are larger than that of X100 pipe. At the same time,The initial CTOD values and the CTOD values withmaximum load of X70 and X80 pipe are larger than that of X100 pipe.The test results suggest that the fracture toughness, crack initiation and propagation resistance of theX70 and X80 pipe are greater than that of X100 pipe, and the mechanismis analyzed finally.

Transformation of BS7448-CTOD to ASTM E1290-CTOD

2008 ◽  
Author(s):  
Yoichi Kayamori ◽  
Takehiro Inoue ◽  
Tetsuya Tagawa
Keyword(s):  
Strain Hardening ◽  
Strain Hardening Exponent ◽  
Test Results ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Edge Notch ◽  
Crack Tip Opening ◽  
The Relationship ◽  
Single Edge Notch Bend

Experimental and analytical investigations into Crack Tip Opening Displacement, CTOD, were conducted to demonstrate the relationship between BS7448-CTOD and ASTM E1290-CTOD. CTOD test results showed that ASTM-CTOD was occasionally much lower than BS-CTOD both in single edge notch bend specimens and in CT specimens for low-strength structural steels, and this tends to be more remarkable in CT specimens. In addition, the analytical results of simplified elastic-plastic facture parameter calculation using the Electric Power Research Institute scheme demonstrated that the ratio of ASTM-CTOD to BS-CTOD was not constant but varied according to CTOD changes. Material factors such as the yield stress, the strain hardening exponent, specimen size and configurations influenced the CTOD ratio, and low strain hardening exponent in the Ramberg-Osgood relation and CT specimen configuration significantly decreased the CTOD ratio. An equation that transforms BS-CTOD into ASTM-CTOD is proposed in this study. This equation gives a good estimate of ASTM-CTOD from BS-CTOD.

Critical Crack Tip Opening Displacement for X70 and X80 Steels - A Parametric Study

2017 ◽  
Vol 898 ◽  
pp. 719-724 ◽  
Author(s):  
Xiao Ben Liu ◽  
Qing Quan Duan ◽  
Bao Dong Wang ◽  
Hong Zhang
Keyword(s):  
Mouth Opening ◽  
High Strength ◽  
Crack Mouth Opening Displacement ◽  
Specimen Thickness ◽  
Pipe Steels ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Line Pipe ◽  
Crack Tip Opening

High strength line-pipe steels are widely used in long distance gas pipelines. Fracture toughness is one major parameter in the performance evaluation of these line-pipe steels. For high strength line-pipe steels, critical crack tip opening displacement (CTOD) is one typical quantity for fracture toughness. In this paper, a series of experimental studies were conducted to investigate the influences of steel property and specimen thickness on critical CTOD by three points bending tests for X70 and X80 line-pipe steel. Results showed that the critical CTOD is mainly depended on the plastic crack mouth opening displacement of the specimen. For the same size specimens, the critical CTOD of X80 steel was much less than X70 steel. The specimen thickness had a significant influence on the plastic crack mouth opening displacement. With the decrease of the specimen thickness, the critical CTOD increased.

Transformation of BS7448-CTOD to ASTM E1290-CTOD

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yoichi Kayamori ◽  
Takehiro Inoue ◽  
Tetsuya Tagawa
Keyword(s):  
Strain Hardening ◽  
Compact Tension ◽  
Strain Hardening Exponent ◽  
Fracture Parameter ◽  
Test Results ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Edge Notch ◽  
Crack Tip Opening ◽  
The Relationship

Experimental and analytical investigations into crack tip opening displacement (CTOD) were conducted to demonstrate the relationship between BS7448-CTOD and ASTM E1290-CTOD. The CTOD test results showed that ASTM-CTOD was occasionally much lower than BS-CTOD both in single edge notch bend specimens and in compact tension (C(T)) specimens for low-strength structural steels, and this tended to be more remarkable in C(T) specimens. In addition, the analytical results of simplified elastic-plastic fracture parameter calculation using the Electric Power Research Institute scheme demonstrated that the ratio of ASTM-CTOD to BS-CTOD was not constant but varied according to CTOD changes. Material factors such as the yield stress, the strain hardening exponent, specimen size and configurations influenced the CTOD ratio, and low strain hardening exponents in the Ramberg–Osgood relation and C(T) specimen configuration significantly decreased the CTOD ratio. An equation that transforms BS-CTOD into ASTM-CTOD is proposed in this study. This equation gives a good estimate of ASTM-CTOD from BS-CTOD.

Experimental Study on Fracture Toughness of Q460C the High-Strength Construction Steel at Low Temperature

2011 ◽  
Vol 71-78 ◽  
pp. 890-897 ◽  
Author(s):  
Yuan Qing Wang ◽  
Yun Lin ◽  
Yan Nian Zhang ◽  
Yong Jiu Shi
Keyword(s):  
Low Temperature ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Function Fitting ◽  
Ductile Brittle Transition Temperature ◽  
Boltzmann Function ◽  
Fracture Appearance ◽  
Crack Tip Opening

Three point bending tests were carried out on 14mm-thick Q460C the high-strength structural steel at low temperature, and scanning electronic microscope of the fracture appearance was analyzed. The results showed that the obvious feature of brittle mechanism was shown on the three point bending specimen fracture whose testing took place at -40°C. And the crack tip opening displacement value of Q460C steel, which was less than that of Q235 steel, Q345 steel and Q390 steel at low temperature, tended to decrease with respect to the temperature reduction. Moreover, a Boltzmann function fitting analysis was applied to the experimental data, and the ductile-brittle transition temperature and the changing regularity were obtained.

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