Research on the Reverse Loading Hardening Model of the X80 Pipeline Steel

2013 ◽  
Vol 750-752 ◽  
pp. 370-374
Author(s):  
Xing Zhou Cai ◽  
Lin Feng Wang ◽  
Shi Yan Zhao ◽  
Bao Feng Guo ◽  
Yu Xin Zhu
Keyword(s):  
Plastic Deformation ◽  
Pipeline Steel ◽  
Strength Properties ◽  
Loading Test ◽  
X80 Pipeline Steel ◽  
Hardening Model ◽  
Material Parameters ◽  
Mixed Hardening ◽  
Reverse Loading ◽  
Hardening Factor

Based on the reverse uniaxial loading test, the influences of the plastic deformation on the strength properties are studied. The softening of the X80 pipeline steel is observed which reveals the hardening type is mixed hardening. The expression of mixed hardening factor M and the material parameters of the nonlinear mixed hardening model under different M can be obtained. The results show that, if the pre-strain increases and ranges from 0.55% to 2.5%, the mixed hardening characteristics of the X80 pipeline steel will be more obvious and its M will also increase.

Modeling Plastic Deformation of Mild Steel Under Nonproportional Deformation Path

1986 ◽  
Vol 108 (3) ◽  
pp. 258-261 ◽  
Author(s):  
A. Gilat
Keyword(s):  
Plastic Deformation ◽  
Mild Steel ◽  
Abrupt Change ◽  
Plastic Strain Rate ◽  
Anisotropic Hardening ◽  
Loading Test ◽  
Deformation Path ◽  
Hardening Model ◽  
Deformation Test ◽  
Tension Loading

An elastic/viscoplastic theory that includes anisotropic strain hardening is used in the analysis of a nonproportional biaxial torsion-tension loading test. The theory is a combination of the formulation of Perzyna [5] and the anisotropic hardening model of Mro´z [6], and is applied in modeling the behavior of mild steel in a nonproportional deformation test reported by Meguid and Malvern [2]. The results show that the theory predicts the material response well. Especially, the theory models adequately the noncoaxiality between the plastic strain rate and the deviatoric stress vectors following an abrupt change in the deformation path.

Fracture Toughness and Application of X80 Pipeline Steel

2019 ◽  
Vol 944 ◽  
pp. 938-943
Author(s):  
Hua Zhang ◽  
Hong Zhang ◽  
Cai Hong Lu
Keyword(s):  
Fracture Toughness ◽  
Acoustic Emission ◽  
Crack Front ◽  
Pipeline Steel ◽  
Heat Affect Zone ◽  
X80 Pipeline Steel ◽  
Material Parameters ◽  
Failure Assessment ◽  
Pipeline Safety ◽  
Metal Weld

The fracture toughness of X80 pipeline steel, which has been widely used in China, plays a key role in pipeline safety insurance. In order to know the accurate fracture toughness of X80, the methods of acoustic emission and high K ratio have been carried out to judge the initiation of crack propagation and improve flatness of fatigue pre-crack front. By this method, fracture toughness of base metal, weld and heat affect zone of X80 pipeline steel have been tested, and failure assessment curves of X80 have been established and fitting equations has been provided. The results suggested that different failure assessment curves should be established according to different crack sizes and material parameters.

Study on Corrosion of X80 Pipeline Steel in Different Water Content of Soil

2014 ◽  
Vol 1015 ◽  
pp. 655-658
Author(s):  
Shu Zhen Yu ◽  
Guang Jun Xu ◽  
Han Hua Song ◽  
Xun Zhu ◽  
Wen We Lu ◽  
...  
Keyword(s):  
Water Content ◽  
High Frequency ◽  
Pipeline Steel ◽  
Electrochemical Corrosion ◽  
High Water ◽  
High Water Content ◽  
Linear Segment ◽  
X80 Pipeline Steel ◽  
The Third ◽  
In The Beginning

The electrochemical corrosion of X80 pipeline steel in Xinzhou’s soil with different water content is tested and analyzed. The corrosion signal time and frequency domain figure show that the corrosion signal fluctuates all the time in 30 days’ test with low water content (14%). The slope of high-frequency linear segment in the potential PSD is smaller than it is at the beginning. In the soil with the middle water content (18%), the intense wave motion lasts for 15 days. The noise fluctuation only exists before the third days when in the high water content soil (22%). After the third day, linear drift can be observed but no transient peak. The slope of high-frequency linear segment changes obviously compared with the situation in the beginning. And the high-frequency white noise appears.

Experimental Analysis of Ratcheting Failure Based on the Piezomagnetic Response of X80 Pipeline Steel

2017 ◽  
Author(s):  
Sheng Bao ◽  
Shengnan Hu ◽  
Yibin Gu
Keyword(s):  
Magnetic Field ◽  
Hysteresis Loop ◽  
Mechanical Response ◽  
Pipeline Steel ◽  
Failure Process ◽  
Failure Behavior ◽  
X80 Pipeline Steel ◽  
Test Analysis ◽  
Number Of Cycles ◽  
The Magnetic Field

The objective of this research is to explore the correlation between the piezomagnetic response and ratcheting failure behavior under asymmetrical cyclic stressing in X80 pipeline steel. The magnetic field variations from cycle to cycle were recorded simultaneously during the whole-life ratcheting test. Analysis made in the present work shows that the piezomagnetic hysteresis loop evolves systematically with the number of cycles in terms of its shape and position. Corresponding to the three-stage process in the mechanical response, piezomagnetic response can also be divided into three principal stages, but the evolution of magnetic parameter is more complex. Furthermore, the loading branch and unloading branch of the magnetic field-stress hysteresis loop separate gradually from each other during ratcheting failure process, leading to the shape of hysteresis loop changes completely. Therefore, the progressive degradation of the steel under ratcheting can be tracked by following the evolution of the piezomagnetic field. And the shape transition of the hysteresis loop can be regarded as an early warning of the ratcheting failure.

Effect of Ferrite Volume Fraction on Mechanical Properties of X80 Pipeline Steel

2014 ◽  
Vol 989-994 ◽  
pp. 212-215
Author(s):  
J. Liu ◽  
G. Zhu ◽  
W. Mao
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Work Hardening ◽  
Single Phase ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
X80 Pipeline Steel ◽  
Hardening Behavior ◽  
Two Phases ◽  
Better Than

The effect of volume fraction of ferrite on the mechanical properties including strength, plasticity and wok hardening was systematically investigated in X80 pipeline steel in order to improve the plasticity. The microstructures with different volume fraction of ferrite and bainite were obtained by heat-treatment processing and the mechanical properties were tested. The work hardening behavior was analyzed by C-J method. The results show that the small amount of ferrite could effectively improve the plasticity. The work hardening ability and the ratio of yield/tensile strength with two phases of ferrite/bainite would be obviously better than that with single phase of bainite. The improvement of plasticity could be attributed to the ferrite in which more plastic deformation was afforded.

Fracture Toughness of Different Locations in API X80 Pipeline Steel on Low Constraint SENT Specimens

2016 ◽  
Vol 853 ◽  
pp. 251-255
Author(s):  
Hong Sheng Lu ◽  
Yong He Yang ◽  
Gang Chen ◽  
Xu Chen ◽  
Xin Wang
Keyword(s):  
Welded Joints ◽  
Weak Link ◽  
Pipeline Steel ◽  
Welding Process ◽  
Resistance Curve ◽  
X80 Pipeline Steel ◽  
Three Samples ◽  
Inner Surface ◽  
Notch Orientation ◽  
Low Constraint

With the considerable use of high-grade pipeline steel in onshore and offshore project, welded joints are recognized as the weak link in pipeline because of the non-uniform microstructural regions induced by welding heat input. At first, the microstructural of different regions in API X80 pipeline welded joints was characterized and quantified by SEM, which indicate that the pipeline steel is a typical acicular ferrite steel. In this paper we investigated the J-integral resistance curve (J-R curve) in different locations of API X80 pipeline welded joints through low constraint SENT specimens with side grooves at room temperature. The effect of notch orientation (longitudinal-radial (L-R) and transverse-radial (T-R)) on resistance curve were investigated in base metal, which reveal the orientation almost have no effect on resistance curve. As the welded joints adopted in this study is two-pass steel arc welds, so the J-R curves of the inner surface, the outer surface and through-thickness surface notches specimens in the weld metal were investigated. The inner surface sample have the highest toughness through three samples because of the effect of second pass welding process. The effect of constraint on resistance curve was conduct between low constraint SENT specimen and high constraint SENB specimen, which found that the lower constraint corresponding to the higher resistance curve. After finishing the test, crack advancing plan of different positions were etched and observed by OM to demonstrate that the crack path always in the region which we would like to test.

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