The Effect of Specimen Orientation and Thickness on the Initiation of Delamination Crack in X80 Pipeline Steel

2013 ◽  
Vol 668 ◽  
pp. 625-629
Author(s):  
Xiao Yu Liu ◽  
Tian Yi Hu ◽  
Zheng Yang
Keyword(s):  
Main Crack ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Interface Strength ◽  
Weak Interface ◽  
X80 Pipeline Steel ◽  
Delamination Crack ◽  
Three Point Bending ◽  
3D Finite Element Method ◽  
Delamination Cracks

The effect of weak interfacial orientation, thickness and the main crack depth on the initiation of delamination crack and main crack in three-point bending specimens of X80 pipeline steel are investigated, using 3D finite element method. Considering the different fracture mechanism of delamination crack and main crack, two different criteria are adopted for them in the simulation. The results reveal that, when the delamination cracks initiates, the initiating position is fixed and the Jz integral of the main crack is a constant for specific weak interfacial orientation specimens with different main crack depth and a certain thickness. When specific weak interfacial orientation specimens have different thickness and a certain main crack depth, the initiating position of delamination crack is equal to the above mentioned, but the Jz integral of the main crack has a ripad decline with the increasing of thickness and then tend to stable. In particular, the delamination crack will not appear for specimens with thin thickness. The thicker the specimen is, the higher the ultimate weak interface strength is needed to prevent the initiation of the delamination crack for specimen with a certain main crack depth. The larger delamination crack will generate, when the specimens have a lower ultimate weak interface strength, a smaller Jz integral of main crack and a larger thickness.

Fracture Appearance Evaluation of High Performance Pipeline Steel DWTT Specimen with Delamination Cracks

2006 ◽  
Vol 324-325 ◽  
pp. 59-62 ◽  
Author(s):  
Zheng Yang ◽  
Wan Lin Guo ◽  
Chun Yong Huo ◽  
Yi Wang
Keyword(s):  
Stress State ◽  
Brittle Fracture ◽  
Fracture Surface ◽  
Main Crack ◽  
High Performance ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Delamination Crack ◽  
Fracture Appearance ◽  
Delamination Cracks

The delamination cracks and its effects on the fracture of pipeline steel are investigated experimentally by using of Drop-Weight Tear Test (DWTT). The delamination cracks are produced by the stress perpendicular to the weak interfaces before main crack beginning or accelerating, no new delamination crack is produced during the stabile propagation of fracture. The quantity, splay degree of delamination crack and the space between two delamination cracks are influenced by the stress state of the crack tip at beginning or accelerating point of main crack and the length of delamination crack is influenced by the stress state of the crack tip during the propagation of fracture. The surface of delamination crack is cleavage fracture appearance with large cleavage facet. There is no delamination crack on the brittle fracture surface below the brittle-to-ductile temperature or on the brittle fracture region of mix-mode fracture surface with ductile and brittle region. The part of fracture surfaces with delamination crack ought to be evaluated as the shear area because the delamination cracks are produced only on the ductile fracture surface or on the ductile part of fracture surface.

Numerical Study of the Crack-Front Constraint for SENT Specimens of X80 Pipeline Steel

2017 ◽  
Vol 898 ◽  
pp. 735-740
Author(s):  
Ting Zhong ◽  
Lin Zhu ◽  
Yan Zhou ◽  
Jian Shuai ◽  
Lan He
Keyword(s):  
Crack Front ◽  
Numerical Study ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Stress Triaxiality ◽  
Width Ratio ◽  
Specimen Thickness ◽  
X80 Pipeline Steel ◽  
Specimen Width ◽  
Average Measure

This work presents a numerical study of crack-front constraint for SENT specimens of X80 pipeline steel, to examine geometry effect on the correlation of crack-front stress field and constraint. An average measure of constraint over crack-front Am was employed to characterize the crack-front constraint. SENT specimens with varying geometries (different crack depth to specimen width ratio, a/W, and different specimen width and thickness, W/B) were analyzed by Gurson-Tvergaard-Needleman model (GTN model). Results showed that the stress triaxiality Am can characterize the crack-front constraint of X80 pipeline steel very well. The level of the Am-△a curve rises with the decrease of crack depth, and increases first and then decreases with the increase of SENT specimen thickness.

Experimental and Finite Element Study on the Fatigue Growth of a Semi-Elliptical Surface Crack in a X80 Pipeline Steel Specimen

2014 ◽  
Vol 580-583 ◽  
pp. 3026-3029 ◽  
Author(s):  
Qiao Jin ◽  
Ze Yu Sun ◽  
Wan Nan Guo
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Test Data ◽  
Surface Crack ◽  
Evolution Equations ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Steel Specimen ◽  
X80 Pipeline Steel ◽  
Depth Direction

In this paper, a fatigue test of a X80 pipeline steel specimen with a semi-elliptical defect was performed to study the fatigue propagation stages of the Surface cracks. Based on the obtained test data, a three dimentional finite element procedure was developed for the crack growth estimation of the surface crack in the specimen. In the numerical analysis of crack growth, both the crack depth direction and the surface direction were investigated by using two different evolution equations. The stress intensity factors along the crack front were determined by applying the virtual crack closure technique. The predictions of crack growth were compared with the test data.

Different Delamination Cracks during Fracture and Their Influences on the Fracture of X70 Pipeline Steel

2008 ◽  
Vol 33-37 ◽  
pp. 91-96
Author(s):  
Zheng Yang ◽  
Hyeon Gyu Beom ◽  
Chang Boo Kim ◽  
Chong Du Cho
Keyword(s):  
Pipeline Steel ◽  
Notch Root ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Strength Distribution ◽  
Stress Fields ◽  
X70 Pipeline Steel ◽  
Delamination Crack ◽  
Delamination Cracks

Single or multiple of delaminations have been found frequently on the fracture surface of X70 pipeline steel. In this study, the delamination cracks and their influence on the fracture of pipeline are investigated by both experiment and three-dimensional fracture analyses. It is shown that the three-dimensional stress state is prerequisite for delamination crack and the strength distribution of material influences the form and direction of delamination crack. The delamination cracks are produced on the weak interfaces among the material by the tensile stress perpendicular to them before the fracture passes. The direction of delamination crack depends on the three-dimensional stress fields and strength distribution of material near the crack tip or notch root. The delamination cracks of the fracture through thickness of pipe wall make the effective thickness decrease and the delamination cracks of surface crack are perpendicular to the direction of fracture propagation direction. The delamination cracks reduce the stress triaxiality near crack tip and in turn, improve the fracture toughness of X70 pipeline steel.

Metal Magnetic Memory Testing of the Drilling Riser Pipeline Steel Based on Pulsating-Impact-Fatigue Test

2020 ◽  
Vol 975 ◽  
pp. 15-24
Author(s):  
Wei Zhou ◽  
Jian Chun Fan ◽  
Xiang Yuan Liu ◽  
Shu Jie Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Damage ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Fatigue Crack Initiation ◽  
Magnetic Memory ◽  
Impact Fatigue ◽  
Fe Method ◽  
X80 Pipeline Steel ◽  
Memory Signals

To know the fatigue damage state of X80 pipeline steel which is used for the drilling riser and prevent the occurrence of fatigue fracture accidents. Pulsating-impact-fatigue tests were conducted in laboratory, magnetic memory signals were measured during the whole fatigue process. The distribution of stress and magnetic field vector with different crack depth was analyzed by using finite element (FE) method. During fatigue crack initiation stage, magnetic signals increased slowly with fatigue loading cycles because of the effect of stress-magnetization. When fatigue crack appeared, magnetic signals were mainly affected by magnetic flux leakage (MFL) which was induced by fatigue crack. Magnetic memory characteristic parameters had a good linear relationship with fatigue crack depth. Magnetic memory signals were able to reflect the change of fatigue damage status.

Application of Constraint Corrected J-R Curves to Fracture Analysis of Pipelines

2005 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Crack Tip ◽  
Mathematical Expression ◽  
Width Ratio ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Element Analysis

Fracture properties of API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimental J-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for X80. It is shown that the predicted J-R curves developed in this paper match well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.

Application of Constraint Corrected J-R Curves to Fracture Analysis of Pipelines

2005 ◽  
Vol 128 (4) ◽  
pp. 581-589 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Crack Tip ◽  
Mathematical Expression ◽  
Width Ratio ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Element Analysis

Fracture properties of an API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for the X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimentalJ-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for the X80. It is shown that the predicted J-R curves developed in this paper agree well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document