Experimental Investigation of Ductile Tearing Properties for API X70 and X80 Pipeline Steels

2005 ◽  
Author(s):  
Mauri´cio Carvalho Silva ◽  
Eduardo Hippert ◽  
Claudio Ruggieri
Keyword(s):  
Pipeline Steel ◽  
Standard Procedure ◽  
Tensile Tests ◽  
Compact Tension ◽  
Propagation Path ◽  
Pipeline Steels ◽  
Ductile Tearing ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Fracture Specimens

This work presents an investigation of the ductile tearing properties for API 5L X70 and X80 pipeline steels using experimentally measured crack growth resistance curves (J-R curves). Testing of the pipeline steels employed compact tension (C(T)) fracture specimens to determine the J-R curves based upon the unloading compliance method using a single specimen technique in accordance with the ASTM E1820 standard procedure. Conventional tensile tests and Charpy V-Notch tests were also performed to determine the mechanical and impact properties for the tested materials. Severe splitting running parallel with the crack propagation path with varied lengths was observed in all tested fracture specimens, particularly for the API X80 material. The occurrence of splits makes the determination of JIc and resistance curves more difficult, as delamination of interfaces positioned normal to the crack front decreases the effective thickness of the test piece, inducing plane stress conditions deep inside the specimen. This experimental characterization provides additional toughness and mechanical data against which the general behavior of X70 and X80 class pipeline steel can be compared.

Evaluation of Crack Growth Resistance Curves for Pipeline Steels Using Constraint Designed Fracture Specimens

2006 ◽  
Author(s):  
Sebastian Cravero ◽  
Claudio Ruggieri
Keyword(s):  
Crack Growth ◽  
Estimation Procedure ◽  
Standard Test ◽  
Crack Growth Resistance ◽  
Test Procedures ◽  
Pipeline Steels ◽  
Wide Range ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Fracture Specimens

This work provides an estimation procedure to determine J-resistance curves for SE(T) fracture specimens using the unloading compliance technique and the eta-method. In the present study, attention is directed to pin-loaded SE(T) specimens with varying geometry and crack sizes but representative solutions are also included for clamped SE(T) specimens. A summary of the methodology upon which J and crack extension are derived sets the necessary framework to determine crack resistance data from the measured load vs. displacement curves. The extensive plane-strain analyses enable numerical estimates of the nondimensional compliance, μ, and parameters η and γ for a wide range of specimen geometries and material properties characteristic of structural and pipeline steels. Laboratory testing of an API 5L X60 steel at room temperature using pin-loaded SE(T) specimens with side-grooves provide the load-displacement data needed to validate the estimation procedure for measuring the crack growth resistance curve for the material. The results presented here produce a representative set of solutions which lend further support to develop standard test procedures for constraint-designed SE(T) specimens applicable in measurements of crack growth resistance for pipelines.

Experimental Evaluation of J Resistance Curves for Ductile Steels Using SE(T) Fracture Specimens

2007 ◽  
Author(s):  
Sebastian Cravero ◽  
Claudio Ruggieri ◽  
Roberto Piovatto ◽  
Waldek W. Bose ◽  
Dirceu Spinelli
Keyword(s):  
Crack Growth ◽  
Oil And Gas ◽  
Pipeline Steel ◽  
High Strength ◽  
Oil And Gas Industry ◽  
Crack Size ◽  
Crack Growth Resistance ◽  
Pipeline Steels ◽  
Resistance Curves ◽  
Fracture Specimens

This work presents an investigation of the ductile tearing properties for an API 5L X60 pipeline steel using experimentally measured crack growth resistance curves (J-R curves). Use of these materials are motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the Brazilian oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline steels employed side-grooved SE(T) specimen with varying crack size to determine the J-R curves based upon the unloading compliance method using a single specimen technique. Recent developed compliance functions and eta-factors applicable for SE(T) fracture specimens are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline steels using SE(T) specimens with varying geometries.

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.

scholarly journals Effect Range of the Material Constraint in Different Strength Mismatched Laboratory Specimens

2020 ◽  
Vol 10 (7) ◽  
pp. 2434 ◽  
Author(s):  
Yue Dai ◽  
Jie Yang ◽  
Haofeng Chen
Keyword(s):  
Crack Propagation ◽  
Fracture Resistance ◽  
Compact Tension ◽  
Propagation Path ◽  
Resistance Curve ◽  
Single Edge ◽  
Integrity Assessment ◽  
Scientific Support ◽  
Resistance Curves ◽  
Initial Cracks

Different strength mismatched laboratory specimens that contain the compact tension (CT), single edge-notched tensile (SENT), and central-cracked tension (CCT) specimens with various specimen geometries, loading configurations, and initial cracks were selected to investigate the effect range of the material constraint systematically. The results showed that the effect range of material constraint exists in all the strength mismatched specimens and structures. The numerical value of the effect range is influenced by the geometry constraint. The high geometry constraint reduces the effect range of material constraint. When a material is located outside the effect range of material constraint, the fracture resistance curves and crack propagation paths of the specimens and structures are no longer influenced by the mechanical properties of the material. In addition, an interaction exists between the geometry constraint and material constraint. The high geometry constraint strengthens the effect of material constraint, whereas the fracture resistance curve and crack propagation path are insensitive to the material constraint under the low geometry constraint. The results in this study may provide scientific support for the structure integrity assessment and the design of strength mismatched structures.

Fracture Mechanics Evaluation of Pipes Subjected to Combined Load Conditions

2009 ◽  
Author(s):  
Sebastian Cravero ◽  
Richard E. Bravo ◽  
Hugo A. Ernst
Keyword(s):  
Fracture Mechanics ◽  
Q Methodology ◽  
Biaxial Loading ◽  
Single Edge ◽  
Computational Cell ◽  
Ductile Tearing ◽  
Combined Load ◽  
Loading Effects ◽  
Resistance Curves ◽  
Fracture Specimens

For certain applications, pipelines may be submitted to biaxial loading situations. In these cases, it is not clear the influence of the biaxial loading on the fracture mechanics behavior of cracked pipelines. For further understanding of biaxial loading effects, this work presents a numerical simulation of ductile tearing in a circumferentially surface cracked pipe under biaxial loading using the computational cell methodology. The model was adjusted with experimental results obtained in laboratory using single edge cracked under tension (SENT) specimens. These specimens appear as the better alternative to conventional fracture specimens to characterize fracture toughness of circumferentially cracked pipes. The negligible effect of biaxial loadings on resistance curves was demonstrated. To guarantee the similarities of stress and strains fields between SENT specimens and cracked pipes subjected to biaxial loading, a constraint study using the J-Q methodology and the h parameter was used. The constraint study gives information about the characteristics of the crack-tip conditions.

Evolution of Plasticity in Relation to Ductile Tearing in 304(L) Stainless Steel

2010 ◽  
Author(s):  
Andrew P. Wasylyk ◽  
Andrew H. Sherry
Keyword(s):  
Fracture Toughness ◽  
Plastic Zone ◽  
Crack Growth ◽  
Structural Integrity ◽  
Plastic Zone Size ◽  
Compact Tension ◽  
Image Correlation ◽  
Ductile Tearing ◽  
Integrity Assessment ◽  
Unloading Compliance

In the structural integrity assessment of structures containing defects, ductile tearing and plastic collapse are treated as competing failure mechanisms. The validity of fracture toughness measurements in test specimens is limited by the development of plasticity ahead of the crack tip. Compact Tension (CT) specimens are commonly used to characterise the ductile fracture toughness. Two sizes of CT specimens (thickness 25 and 15mm) were tested using the unloading compliance technique and the J-Resistance curve characterised. Concurrently, the development of the plastic zone was monitored on the surface of specimens using digital image correlation. This enabled the plastic zone size to be correlated with the evolution of crack growth. It was found that in both specimens no crack growth had occurred prior to plastic yielding of the un-cracked ligament on the specimen surface.

Crack Growth Testing of an X80 Pipeline Girth Weld Using SE(T) and SE(B) Fracture Specimens

2012 ◽  
Author(s):  
Leonardo L. S. Mathias ◽  
Diego F. S. Burgos ◽  
Gustavo H. B. Donato ◽  
Marcelo Paredes ◽  
Claudio Ruggieri
Keyword(s):  
Crack Growth ◽  
Pipeline Steel ◽  
Oil And Gas Industry ◽  
Crack Growth Resistance ◽  
Homogeneous Material ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Resistance Curves ◽  
Girth Welds ◽  
Fracture Specimens

Accurate measurements of fracture resistance properties, including crack growth resistance curves for pipeline girth welds, become essential in defect assessment procedures of the weldment region and the heat affected zone, where undetected cracklike defects (such as lack of penetration, deep undercuts, root cracks, etc.) may further extend due to to high tension stresses and strains. This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves ((J-Δa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized side-grooved, clamped single edge notched tensiles (SE (T)) specimens and three-point (3P) bend single edge bend (SE(B)) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. Recently developed compliance functions and η-factors applicable for SE (T) and SE(B) fracture specimens with homogeneous material and overmatch welds are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE (T) and SE(B) specimens with weld centerline cracks.

J-R Curve Testing of SE(T) Fracture Specimens Using Unloading Compliance and CMOD Data

2008 ◽  
Author(s):  
Sebastian Cravero ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Test Procedure ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Test Technique ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Resistance Data ◽  
Fracture Specimens

Laboratory testing of fracture specimens to measure resistance curves (J - Δa) have focused primarily on the unloading compliance method using a single specimen. Current estimation procedures (which form the basis of ASTM E1820 standard) employ load line displacement (LLD) records to measure fracture toughness resistance data incorporating a crack growth correction for J. An alternative method which potentially simplifies the test procedure involves the use of crack mouth opening displacement (CMOD) to determine both crack growth and J. This study provides further developments of the evaluation procedure for J in cracked bodies that experience ductile crack growth based upon the eta-method and CMOD data. The methodology broadens the applicability of current standards adopting the unloading compliance technique in laboratory measurements of fracture toughness resistance data (J resistance curves). The developed J evaluation formulation for growing cracks based on CMOD data provides a viable and yet simpler test technique to measure crack growth resistance data for ductile materials.

Constraint Effect on the Ductile Fracture Behavior of High-Strength Pipeline Steels

2016 ◽  
Vol 850 ◽  
pp. 899-904
Author(s):  
Jie Xu ◽  
Xiao Min Zhuo ◽  
Peng Peng Li ◽  
Yu Fan ◽  
Zhi Sun
Keyword(s):  
Fracture Behavior ◽  
Hoop Stress ◽  
High Strength ◽  
Minor Effect ◽  
Pipeline Steels ◽  
Ductile Tearing ◽  
Resistance Curves ◽  
A Minor ◽  
Internal Pressures ◽  
Senb Specimen

This work presents an investigation of the ductile tearing properties for a pipe with internal and external circumferential cracks using 2D plane strain and axisymmetric models. Crack growth resistance curves were computed using the complete Gurson model. The pipes with various crack depths and internal pressures were analyzed. The results were compared with those of corresponding SENT and SENB specimens. It clearly indicated a significant effect of constraint on the resistance curves for internal and external cracked pipes. A minor effect of hoop stress induced by internal pressure on the CTOD-resistance curves is expected for deep-cracked pipes. The SENT specimen is a better representation of circumferentially flawed pipes and an alternative to the conventional standard SENB specimen for the fracture mechanics testing in engineering critical assessment of high-strength pipeline steels.

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