Experimental Determination of Constraint Dependent J-R Curves for X80 Pipeline Steel Using Normalization Method

2006 ◽  
Author(s):  
Xi. K. Zhu ◽  
B. N. Leis ◽  
G. Shen ◽  
W. R. Tyson
Keyword(s):  
Pipeline Steel ◽  
Crack Tip ◽  
Normalization Method ◽  
Resistance Curve ◽  
X80 Pipeline Steel ◽  
Basic Procedure ◽  
Unloading Compliance ◽  
Crack Tip Constraint ◽  
Cracked Specimens ◽  
Elastic Unloading

The normalization method is adopted for standard specimens and extended for nonstandard specimens in this paper to develop J-R curves for X80 pipeline steel directly from load versus load-line displacement records without the need of crack length measurement. Standard deep cracked specimens usually contain high crack-tip constraint, while nonstandard shallow cracked specimens involve low crack-tip constraint. To examine constraint effect on fracture toughness, six single-edge notched bend (SENB) specimens with different crack lengths for an X80 pipeline steel are tested according to ASTM standard E1820-05. The normalization method is then used to determine the constraint dependent J-R curves for these SENB specimens. To validate the experimental results obtained from the normalization method, the conventional elastic unloading compliance method is also used to measure crack extension, and determine the J-R curves for the X80 steel. The results show that the J-R curves determined using the normalization method agree well with those based on the elastic unloading compliance method for all SENB specimens, except for those experiencing severe splitting. Therefore, the normalization method can be used to determine J-R curves for the X80 pipeline steel for standard as well as nonstandard specimens. In determining the J-integral values, the resistance curve procedure, the basic procedure and the modified basic procedure specified in ASTM E1820-05 are evaluated. Comparisons of the resulting J-R curves indicate that the modified basic procedure can be equivalent to the resistance curve procedure.

J-Resistance Curve Testing Using Modified Normalization Method for SENT Specimens

2019 ◽  
Vol 795 ◽  
pp. 367-374
Author(s):  
Zheng Liu ◽  
Xin Wang ◽  
Xu Chen
Keyword(s):  
Pipeline Steel ◽  
Cost Effective ◽  
Normalization Method ◽  
Resistance Curve ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
X80 Steel ◽  
Unloading Compliance ◽  
Better Than

A modified normalization (NM) method to determine J-R curves using clamped single edge notched tension (SENT) specimens was proposed. To validate and quantify the modified NM method, the J-R curves of X80 pipeline steel obtained by NM method are compared with those determined by the unloading compliance (UC) method for SENT specimens. The comparison shows that modified NM method is obvious better than unmodified NM method for SENT specimens. The modified NM method has great agreements with UC method, and is a valid and cost-effective tool to be applied to obtain J-R curves of API X80 steel using SENT specimens with shallow cracked depth to deep cracked depth.

Bending Modified J-Q Theory and Its Application to Fracture Constraint Analysis

2007 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Pipeline Steel ◽  
Crack Tip ◽  
Bending Stress ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Q Theory ◽  
Constraint Analysis ◽  
Scale Yielding ◽  
Crack Tip Constraint ◽  
Fracture Constraint

The J-Q theory [1,2] can characterize the crack-tip fields and quantify fracture constraints for various geometric and loading configurations in elastic-plastic materials, but it fails to do so for bending-dominant geometries at large-scale yielding (LSY). This issue significantly restricts its applications to fracture constraint analysis. A modification of the J-Q theory is thus proposed in this paper as a three-term solution with an additional term to address the global bending stress to offset this restriction. The nonlinear global bending stress is linearly approximated in the region of interest at LSY. To verify the bending-modified J-Q solution, detailed elastic-plastic finite element analysis (FEA) is carried out under plane strain conditions for three conventional bending specimens, i.e., single edge notched bend (SENB), single edge notched tension (SENT) and compact tension (CT) specimens for X80 pipeline steel. Deformation considered varies from small-scale yielding (SSY) to LSY. The results show that the bending modified J-Q solution can well match FEA results of crack-tip stress fields for the bending specimens at all deformation levels from SSY to LSY, and the modified parameter Q is a load- and distance-independent constraint parameter at LSY. Thus, the modified parameter Q can be effectively used to quantify the crack-tip constraint for bending geometries. Its application to fracture constraint analysis is demonstrated by ranking crack-tip constraint levels for fracture specimens and by determining constraint corrected J-R curves for the X80 pipeline steel.

Determination of J-R Curves for A285 Carbon Steel Using Normalization Method

2006 ◽  
Author(s):  
X. K. Zhu ◽  
Y. J. Chao ◽  
P. S. Lam
Keyword(s):  
Carbon Steel ◽  
Crack Length ◽  
Electric Potential ◽  
Potential Drop ◽  
Normalization Method ◽  
Resistance Curve ◽  
Drop Method ◽  
Basic Procedure ◽  
Crack Tip Constraint

The normalization method is adopted and extended in this paper to develop J-R curves for standard and nonstandard specimens directly from load versus load-line displacement test data without the need for online crack length measurement. A set of single edge notched bend (SENB) specimens with different crack lengths for an A285 carbon steel are tested according to the guideline of ASTM standard E1820, and the ability of normalization method is then demonstrated in determination of crack-tip constraint-dependent J-R curves for the SENB specimens. The results show that the normalization method can be used to determine J-R curves for the standard as well as nonstandard specimens. The resistance curve procedure and the basic procedure specified in ASTM E1820 are evaluated, and a modified basic procedure is also presented for determining the J-integral. Comparisons of the resulting J-R curves indicate that the modified basic procedure can be equivalent to the resistance curve procedure. To validate the normalization method, the conventional electric potential drop method is used to monitor crack growth and to determine the J-R curves for the A285 steel. Two equations used in the potential drop method, i.e. linear and nonlinear relationships between the crack length and the electric potential, are employed to determine the crack length during the fracture testing. It shows that the J-R curves determined with the normalization method are in good agreement with those based on the potential drop methods for all specimens considered.

Determination of J-R Curve for X60 Pipeline Steel Using SENT Specimens and Normalization Method

2009 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Sebastian Cravero ◽  
Claudio Ruggieri
Keyword(s):  
Crack Extension ◽  
Pipeline Steel ◽  
Cost Effective ◽  
Normalization Method ◽  
J Integral ◽  
Single Edge ◽  
Unloading Compliance ◽  
Elastic Unloading ◽  
Unloading Compliance Method

The normalization method is adopted in this paper to determine J-R curves for X60 pipeline steel using single-edge notched tension (SENT) specimens. A resistance curve procedure associated with the normalization method is developed to estimate crack extension, calculate crack growth corrected J-integral and generate a J-R curve directly using load-displacement data from a single test on SENT specimens. Based on experimental data for a typical pin-loaded SENT specimen, J-R curve for X60 pipeline steel is obtained by the normalization method and the conventional elastic unloading compliance method. The results show that the normalization method is simple and cost-effective, and can obtain J-R curves equivalent to the unloading compliance method in use of SENT specimens.

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.

Prediction of Failure Behavior for Nuclear Piping Using Curved Wide-Plate Test

2004 ◽  
Vol 126 (4) ◽  
pp. 419-425 ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Chang-Ryul Pyo
Keyword(s):  
Fracture Toughness ◽  
Three Dimensional ◽  
Crack Tip ◽  
Full Scale ◽  
Failure Behavior ◽  
Resistance Curve ◽  
Testing Specimen ◽  
Plate Test ◽  
Crack Tip Constraint ◽  
Three Dimensional Finite Element

One important element of the Leak-Before-Break analysis of nuclear piping is how to determine relevant fracture toughness (or the J-resistance curve) for nonlinear fracture mechanics analysis. The practice to use fracture toughness from a standard C(T) specimen is known to often give conservative estimates of toughness. To improve the accuracy of predicting piping failure, this paper proposes a new method to determine fracture toughness using a nonstandard testing specimen, curved wide-plate in tension. To show validity of the proposed curved wide-plate test, the J-resistance curve from the full-scale pipe test is compared with that from the curved wide-plate test and that from C(T) specimen. It is shown that the J-resistance curve from the curved wide-plate tension test is similar to, but that from the C(T) specimen is lower than, the J-resistance curve from the full-scale pipe test. Further validation is performed by investigating crack-tip constraint conditions via detailed three-dimensional finite element analyses, which shows that the crack-tip constraint condition in the curved wide-plate tension specimen is indeed similar to that in the full-scale pipe under bending.

An Experimental Study on J(CTOD)-R Curves of Single Edge Tension Specimens for X80 Steel

2012 ◽  
Author(s):  
Enyang Wang ◽  
Wenxing Zhou ◽  
Guowu Shen ◽  
Daming Duan
Keyword(s):  
Crack Length ◽  
Crack Tip ◽  
Initial Crack ◽  
Single Edge ◽  
X80 Steel ◽  
Toughness Testing ◽  
Unloading Compliance ◽  
Crack Tip Constraint ◽  
The Impact ◽  
Edge Tension

Fracture toughness testing of SE(T) and SE(B) specimens is carried out to experimentally develop J(CTOD)-R curves for the X80 steel based on the unloading compliance method. Six clamped (two shallow-cracked side-grooved, two deep-cracked side-grooved, and two deep-cracked plain-sided) SE(T) and two shallow-cracked side-grooved SE(B) specimens are tested. The impact of crack length on the J(CTOD)-R curves of the SE(T) specimens is investigated. The J(CTOD)-R curves of the shallow-cracked SE(T) specimens are significantly higher than those of the deep-cracked SE(T) specimens once the crack extension exceeds 0.5 mm. A comparison of the J(CTOD)-R curves associated with the SE(B) and SE(T) specimens suggests that the crack tip constraint for the SE(T) specimens is lower than that of the SE(B) specimens with the same nominal initial crack length, and that shallow-cracked SE(T) specimens have less constraint at the crack tip than deep-cracked SE(T) specimens.

Evaluation of Ductile Tearing of X-80 Pipeline Girth Welds Using SE(T), SE(B) and C(T) Fracture Specimens

2013 ◽  
Author(s):  
Leonardo L. S. Mathias ◽  
Diego F. B. Sarzosa ◽  
Claudio Ruggieri
Keyword(s):  
Structural Component ◽  
Structural Integrity ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Pipeline Steels ◽  
Ductile Tearing ◽  
Resistance Curves ◽  
Girth Welds ◽  
Crack Tip Constraint ◽  
Integrity Assessments

Structural integrity assessments of pipe girth welds play a key role in design and safe operation of piping systems, including deep water steel catenary risers. Current methodologies for structural integrity assessments advocate the use of geometry dependent resistance curves so that crack-tip constraint in the test specimen closely matches the crack-tip constraint for the structural component. Testing standards now under development to measure fracture resistance of pipeline steels (J and CTOD) most often employ single edge notched specimens under tension (SENT) to match a postulated defect in the structural component. This paper presents an investigation of the ductile tearing properties for a girth weld of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-R curves). Testing of the girth weld pipeline steels employed clamped SE(T) specimen with center-crack weld and three-point bending SE(B) (or SENB) specimens to determine the J-R curves. Tests involving SE(B) specimens are usually considered conservative, however, the comparison between this two methods may point an accurate alternative for girth weld assessments, since adequate geometry is adopted to describe accurately the structure’s behavior.

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.

Sign in / Sign up

Export Citation Format

Share Document