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.

scholarly journals Evaluation of ductile tearing for API-5L X70 pipeline grade steel using SENT specimens

2015 ◽  
Vol 6 (3) ◽  
pp. 8
Author(s):  
Nicholas Ohms ◽  
Diego Belato Rosado ◽  
Wim De Waele
Keyword(s):  
Crack Growth ◽  
Crack Extension ◽  
Crack Growth Resistance ◽  
Fracture Surfaces ◽  
Edge Notch ◽  
Resistance Curves ◽  
Unloading Compliance ◽  
Inner Diameter ◽  
Tearing Resistance ◽  
Hardness Map

Pipelines in harsh environments may be subjected to large deformations. Classic stress-based design needs to be complemented with strain-based design. An important parameter in the design is the crack growth resistance. SENT testing (Single Edge Notch Tension) allows to determine the so-called material’s tearing resistance curve. Very recently the first standard on SENT testing, BS 8571:2014, has been published. SENT testing is however still subject to extensive research and different approaches with respect to eg. notch placement, crack extension measurement and analysis exist. In this paper two methods for calculating crack extension based on the unloading compliance procedure are used and compared, proving that they show little difference. This is performed on an API-5L X70 steel grade and this for different configurations, namely an inner diameter notch and a through thickness notch. The results showed little difference between the different configurations, although the inner diameter showed higher crack growth resistance. Furthermore, the results are compared to visual observations of the fracture surfaces and a hardness map. The fracture surfaces corresponded to the obtained resistance curves. However, no real correlation between the hardness map and the other results could be seen.

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.

Further Insights on J-R Curve Behavior in Pipeline Steels Using Low Constraint Fracture Specimens

2013 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Claudio Ruggieri
Keyword(s):  
Crack Growth ◽  
Crack Tip ◽  
Stable Crack Growth ◽  
Primary Objective ◽  
Crack Growth Resistance ◽  
Tensile Fracture ◽  
Width Ratio ◽  
Pipeline Steels ◽  
Cell Parameters ◽  
Fracture Specimens

This work addresses a two-parameter description of crack-tip fields in bend and tensile fracture specimens incorporating the evolution of near-tip stresses following stable crack growth with increased values of the J-integral. The primary objective is to examine the potential coupled effects of geometry and ductile tearing on crack-tip constraint as characterized by the J-Q theory which enables more accurate correlations of crack growth resistance behavior in conventional fracture specimens. Plane-strain, finite element computations including stationary and growth analyses are described for SE(B) and clamped SE(T) specimens having different notch depth to specimen width ratio in the range 0.2≤ a/W≤0.5. A computational cell methodology to model Mode I crack extension in ductile materials is utilized to describe the evolution of J with Δa for the fracture specimens. Laboratory testing of an API 5L X70 steel using deeply cracked C(T) specimens is used to measure the crack growth resistance curve for the material and to calibrate the cell parameters. The present results provide additional understanding of the effects of constraint on crack growth which contributes to further evaluation of crack growth resistance properties of pipeline steels using SE (T) and SE(B) specimens.

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.

Comparison of Fracture Toughness Curves Obtained by Single and Multi-Specimen Methodologies for a Pipe Having an Undermatched Girth Weld

2020 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
R. Savioli ◽  
C. Ruggieri ◽  
Alexandre Galiani Garmbis
Keyword(s):  
Carbon Steel ◽  
Crack Growth ◽  
Pipeline Steel ◽  
Crack Growth Resistance ◽  
Inconel 625 ◽  
External Diameter ◽  
Chromium Alloy ◽  
Nickel Chromium ◽  
Wide Range ◽  
Resistance Curves

Abstract Preventing catastrophic failure of engineering components is critical during the exploration and production of oil and gas resources from the offshore deep-water fields in Brazil. Pre-salt reserves are associated with high concentration of aggregated elements to hydrocarbons, particularly carbon dioxide (CO2) and hydrogen sulfide (H2S) which, in the presence of water can produce highly corrosive elements. One solution to this problem is to apply a metal liner made of corrosion-resistant alloy (CRA) internally to the carbon steel pipe. Such a bi-metallic configuration, commonly referred to as a lined pipe or clad pipe, consists essentially of a relatively thin CRA material pipe physically or metallurgically joined to the main carbon steel outer pipe. This experimental study presents an investigation of the ductile tearing properties for the girth weld of a typical C-Mn pipe internally clad with Inconel 625 CRA alloy using experimentally measured crack growth resistance curves. Here, the material of the external pipe is an API 5L Grade X65 pipeline steel and the inner clad layer is made of Inconel nickel-chromium alloy 625 (UNS N06625). The higher mechanical strength and superior resistance to a wide range of corrosive environments of unusual severity for this material derived from the combination of the nickel-chromium matrix with other microalloying elements. Testing of the pipeline girth welds employed clamped SE(T) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen method and the multi-specimen technique. The SE(T) specimens were extracted from a clad pipe having an external diameter of 220 mm and thickness of 23 mm. Further, the current experimental characterization provides toughness data that serve to evaluate the effectiveness of current procedures in determining accurate experimentally measured R-curves for this class of material.

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.

Application of the R-Curve Concept to Fatigue Crack Growth

1978 ◽  
Vol 100 (4) ◽  
pp. 416-420 ◽  
Author(s):  
D. P. Wilhem ◽  
M. M. Ratwani
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Extension ◽  
Stress Ratio ◽  
Cyclic Stress ◽  
Crack Growth Resistance ◽  
Resistance Curve ◽  
Cyclic Stress Ratio ◽  
Wide Range

Crack growth resistance for both static (rising load) and for cyclic fatigue crack growth has been shown to be a continuous function over a range of 0.1 μm to 10 cm in crack extension for 2024-T3 aluminum. Crack growth resistance to each fatigue cycle of crack extension is shown to approach the materials ordinary undirectional static crack resistance value when the cyclic stress ratio is zero. The fatigue crack extension is averaged over many cycles and is correlated with the maximum value of the crack tip stress intensity, Kmax. A linear plot of crack growth resistance for fatigue and static loading data shows similar effects of thickness, stress ratio, and other parameters. The effect of cyclic stress ratio on crack growth resistance for 2219 aluminum indicates the magnitude of differences in resistance when plotted to a linear scale. Prediction of many of these trends is possible using one of several available crack growth data correlating techniques. It appears that a unique resistance curve, dependent on material, crack orientation, thickness, and stress/physical environment, can be developed for crack extensions as small as 0.076 μm (3 μ inches). This wide range, crack growth resistance curve is seen of immense potential for use in both fatigue and fracture studies.

Effects of Weld Strength Mismatch on Estimation Procedures for J and CTOD Fracture Parameters Using SE(B) Specimens

2007 ◽  
Author(s):  
Gustavo H. B. Donato ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Estimation Procedure ◽  
Primary Objective ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Fracture Parameters ◽  
Wide Range ◽  
Estimation Procedures ◽  
Fracture Specimens

This work presents an exploratory development of J and CTOD estimation procedures for welded fracture specimens under bending based upon plastic eta factors and plastic rotation factors. The techniques considered include: i) estimating J and CTOD from plastic work and ii) estimating CTOD from the plastic rotational factor. The primary objective is to gain additional understanding on the effect of weld strength mismatch on estimation techniques to determine J and CTOD fracture parameters for a wide range of a/W-ratios and mismatch levels. Very detailed non-linear finite element analyses for plane-strain models of SE(B) fracture specimens with center cracked, square groove welds provide the evolution of load with increased load-line displacement and crack mouth opening displacement which are required for the estimation procedure. The results show that levels of weld strength mismatch within the range ±20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials, particularly for deeply cracked fracture specimens. The present analyses, when taken together with previous studies, provide a fairly extensive body of results which serve to determine parameters J and CTOD for different materials using bend specimens with varying geometries and mismatch levels.

Sign in / Sign up

Export Citation Format

Share Document