Tensile Strain Capacity of X80 Pipeline Under Tensile Loading With Internal Pressure

2010 ◽  
Author(s):  
Satoshi Igi ◽  
Takahiro Sakimoto ◽  
Nobuhisa Suzuki ◽  
Ryuji Muraoka ◽  
Takekazu Arakawa
Keyword(s):  
Internal Pressure ◽  
Driving Force ◽  
Tensile Strain ◽  
Surface Defects ◽  
Axial Loading ◽  
Element Analysis ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
High Internal Pressure ◽  
Tensile Strain Capacity

This paper presents the results of experimental and finite element analysis (FEA) studies focused on the tensile strain capacity of X80 pipelines under large axial loading with high internal pressure. Full-pipe tensile test of girth welded joint was performed using high-strain X80 linepipes. Curved wide plate (CWP) tests were also conducted to verify the strain capacity under a condition of no internal pressure. The influence of internal pressure was clearly observed in the strain capacity. Critical tensile strain is reduced drastically due to the increased crack driving force under high internal pressure. In addition, SENT tests with shallow notch specimens were conducted in order to obtain a tearing resistance curve for the simulated HAZ of X80 material. Crack driving force curves were obtained by a series of FEA, and the critical global strain of pressurized pipes was predicted to verify the strain capacity of X80 welded linepipes with surface defects. Predicted strain showed good agreement with the experimental results.

Tensile Strain Capacity of X80 Girth Welded Linepipes and Crack Growth Analysis

2012 ◽  
Author(s):  
Satoshi Igi ◽  
Takahiro Sakimoto ◽  
Shigeru Endo ◽  
Ryuji Muraoka ◽  
Takekazu Arakawa
Keyword(s):  
Internal Pressure ◽  
Driving Force ◽  
Tensile Strain ◽  
Axial Loading ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Strain Behavior ◽  
Welded Pipe ◽  
High Internal Pressure ◽  
Tensile Strain Capacity

This paper examines the tensile strain capacity of girth welded pipelines. A pressurized and no pressurized full-pipe tension tests were conducted together with FE analyses in order to investigate the strain behavior of pipe under large axial loading with high internal pressure. The critical tensile strain drastically decreased under a high internal pressure condition. Single edge notch tension (SENT) tests with shallow notched specimens were also performed to obtain the material resistance curve (R-curve), and a series of FE analyses was conducted to obtain the crack driving force for ductile crack propagation. The R-curve and crack driving force curve were used in predicting the tensile strain limit of X80 girth welded pipe with a surface defect in the HAZ. The predicted critical tensile strain showed good agreement with that obtained in the pressurized and no pressurized full-pipe tension test.

Multi-Tier Tensile Strain Models for Strain-Based Design: Part 2 — Development and Formulation of Tensile Strain Capacity Models

2012 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang ◽  
Yaxin Song ◽  
David Horsley ◽  
Steve Nanney
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Weld Strength ◽  
Experiment Data ◽  
Pipe Wall Thickness ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

This is the second paper in a three-paper series related to the development of tensile strain models. The fundamental basis of the models [1] and evaluation of the models against experiment data [2] are presented in two companion papers. This paper presents the structure and formulation of the models. The philosophy and development of the multi-tier tensile strain models are described. The tensile strain models are applicable for linepipe grades from X65 to X100 and two welding processes, i.e., mechanized GMAW and FCAW/SMAW. The tensile strain capacity (TSC) is given as a function of key material properties and weld and flaw geometric parameters, including pipe wall thickness, girth weld high-low misalignment, pipe strain hardening (Y/T ratio), weld strength mismatch, girth weld flaw size, toughness, and internal pressure. Two essential parts of the tensile strain models are the crack driving force and material’s toughness. This paper covers principally the crack driving force. The significance and determination of material’s toughness are covered in the companion papers [1,2].

Design of the Full Scale Experiments for the Testing of the Tensile Strain Capacity of X52 Pipes With Girth Weld Flaws Under Internal Pressure and Tensile Displacement

2014 ◽  
Author(s):  
Celal Cakiroglu ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Tensile Strain ◽  
Oil And Gas ◽  
Full Scale ◽  
Element Analysis ◽  
Simultaneous Application ◽  
Strain Capacity ◽  
Tensile Strain Capacity

Pipelines can be subjected to significant amounts of tensile forces due to geotechnical movements like slope instabilities and seismic activities as well as due to frost heave and thaw cycles in arctic regions. The tensile strain capacity εtcrit of pipelines is crucial in the prediction of rupture and loss of containment capability in these load cases. Currently the Oil and Gas Pipeline Systems code CSA Z662-11 0 contains equations for the prediction of εtcrit as a function of geometry and material properties of the pipeline. These equations resulted from extensive experimental and numerical studies carried out by Wang et al [2]–[6] using curved wide plate tests on pipes having grades X65 and higher. Verstraete et al 0 conducted curved wide plate tests at the University of Ghent which also resulted in tensile strain capacity prediction methods and girth weld flaw acceptability criteria. These criteria are included in the European Pipeline Research Group (EPRG) Tier 2 guidelines. Furthermore Verstrate et al 0 introduced a pressure correction factor of 0.5 in order to include the effect of internal pressure in the tensile strain capacity predictions in a conservative way. Further research by Wang et al with full scale pipes having an internal pressure factor of 0.72 also showed that εtcrit decreases in the presence of internal pressure [10]–[15]. In their work, Wang et al presented a clear methodology for the design of full scale experiments and numerical simulations to study the effect of internal pressure on the tensile strain capacity of pipes with girth weld flaws [10]–[15]. However, there has been limited testing to enable a precise understanding of the tensile strain capacity of pipes with grades less than X65 as a function of girth weld flaw sizes and the internal pressure. In this paper the experimental setup for the testing of grade X52 full scale specimens with 12″ diameter and ¼″ wall thickness is demonstrated. In the scope of this research 8 full scale specimens will be tested and the results will be used to formulate the tensile strain capacity of X52 pipes under internal pressure. The specimens are designed for the simultaneous application of displacement controlled tensile loading and the internal pressure. Finite element analysis is applied in the optimization process for the sizes of end plates and connection elements. Also the lengths of the full scale specimens are determined based on the results from finite element analysis. The appropriate lengths are chosen in such a way that between the location of the girth weld flaw and the end plates uniform strain zones could be obtained. The internal pressure in these experiments is ranging between pressure values causing 80% SMYS and 30% SMYS hoop stress. The end plates and connection elements of the specimens are designed in such a way that the tensile displacement load is applied with an eccentricity of 10% of the pipe diameter with the purpose of increasing the magnitude of tensile strains at the girth weld flaw location. The results of two full scale experiments of this research program are presented. The structural response from the experiments is compared to the finite element simulation. The remote strain values of the experiment are found to be higher than the εtcrit values predicted by the equations in 0.

scholarly journals The influence of material anisotropy and spiral welding on tensile strain capacity of spiral welded pipes

2015 ◽  
Vol 6 (3) ◽  
pp. 9
Author(s):  
Michiel De Backer ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Pipeline Steel ◽  
Experimental Testing ◽  
Outcome Analysis ◽  
Mode Iii ◽  
Plane Shear ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Tensile Strain Capacity

The longitudinal strain capacity of spiral welded pipelines displays to some extents unexplained behaviour. Therefore, they are not (yet) used extensively in offshore applications and harsh conditions, demanding a strain based design. An important factor that influences the tensile strain capacity is the quantity of anisotropy in terms of strength and toughness. Starting from an anisotropic hot rolled highstrength steel skelp, the process of helical forming and post-treating of the pipe adds heterogeneity and changes the level of anisotropy of the product. A parameter that should be examined with respect to anisotropy is the crack driving force, a measure for the toughness of the pipeline steel. Additional to the mode I loading (opening of the crack), the mode III component drives the in-plane shear motion of a crack in the spiral weld when the pipe is subjected to longitudinal deformation. This action, not present inlongitudinal welded pipes, shows a decreasing contribution with increasing plasticity. FE simulations have demonstrated a rise of crack driving force in anisotropic cases with respect to an isotropic reference. However, exact data and variation of various parameters, along with experimental testing need to be conducted. The outcome analysis of such simulations and tests can validate existing models, or help create a better understanding of anisotropic and heterogenic influences on the tensile strain capacity of spiral welded pipes.

Estimation of Tensile Strain Capacity of Vintage Girth Welds

2020 ◽  
Author(s):  
Bo Wang ◽  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Otto Jan Huising
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Software Tool ◽  
Ground Movement ◽  
Small Scale ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Girth Welds ◽  
The Impact ◽  
Tensile Strain Capacity

Abstract Being able to estimate the tensile strain capacity (TSC) of vintage girth welds is sometimes necessary for the integrity management of vintage pipelines. Assessing girth weld integrity could be a top priority after a confirmed ground movement event. Decisions may also be needed about the disposition of a girth weld when weld anomalies are found. Typical fitness-for-service (FFS) procedures, such as API 1104 Annex A and API 579/ASME FFS-1, generally target materials under nominally elastic conditions and strain demands less than 0.2%. These procedures may produce overly conservative results when the strain demand exceeds 0.2%. This paper summarizes the development and validation of a TSC estimation tool for vintage girth welds under PRCI funding. The work consisted of three components: the development of a TSC model for vintage girth welds, the implementation of the model into a software tool, and the experimental validation of the performance of the tool using curved wide plate (CWP) tests. The TSC model was developed following the procedures established through a previous PRCI-PHMSA cofounded work. Finite element analyses (FEA) were performed to obtain a crack-driving force database while considering the salient features of vintage girth welds, such as larger weld caps and weld strength mismatch levels. The TSC model was then derived from the crack-driving force database using apparent toughness values representative of vintage girth welds. A graphical user interface (GUI) and a user manual were developed to facilitate the application of the TSC model. The software tool produces TSC estimates based on geometry, material, loading, and flaw characteristics of a girth weld. For inputs that might not have readily available values, recommended values are provided. The tool allows the evaluation of the impact of various input parameters on TSC. The performance of the TSC estimation tool was evaluated against eight purposely designed CWP tests. Accompanying small-scale material characterization tests, including chemical composition, round bar tensile, microhardness, and Charpy impact tests, were performed to provide additional inputs for the evaluation of the tool. The tool is shown to provide reasonably conservative estimates for TSC. An example problem is presented to demonstrate the application of the tool. Gaps and future work to improve the tool are highlighted at the end of the paper.

J and CTOD Based Tensile Strain Capacity Prediction for Pipelines with a Surface Crack in Girth Weld

2021 ◽  
Author(s):  
Youn-Young Jang ◽  
Nam-Su Huh ◽  
Ik-Joong Kim ◽  
Young-Pyo Kim
Keyword(s):  
Crack Initiation ◽  
Internal Pressure ◽  
Surface Crack ◽  
Driving Force ◽  
Tensile Strain ◽  
Structural Integrity ◽  
Accurate Estimation ◽  
Long Distance ◽  
Crack Driving Force ◽  
Girth Welding

Abstract Long-distance pipelines for the transport of oil and natural gas to onshore facilities are mainly fabricated by girth welding, which has been considered as a weak location for cracking. Pipeline rupture due to crack initiation and propagation in girth welding is one of the main issues of structural integrity for a stable supply of energy resources. The crack assessment should be performed by comparing the crack driving force with fracture toughness to determine the critical point of fracture. For this reason, accurate estimation of the crack driving force for pipelines with a crack in girth weld is highly required. This paper gives the newly developed J-integral and crack-tip opening displacement (CTOD) estimation in a strain-based scheme for pipelines with an internal surface crack in girth weld under axial displacement and internal pressure. For this purpose, parametric finite element analyses have been systematically carried out for a set of pipe thicknesses, crack sizes, strain hardening, overmatch and internal pressure conditions. Using the proposed solutions, tensile strain capacities (TSCs) were quantified by performing crack assessment based on crack initiation and ductile instability and compared with TSCs from curved wide plate tests to confirm their validity.

Effects of Biaxial Loading on the Tensile Strain Capacity of Girth Welds With Weld Strength Undermatching and HAZ Softening

2020 ◽  
Author(s):  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Xiaotong Chen ◽  
David Warman
Keyword(s):  
Internal Pressure ◽  
Tensile Strain ◽  
Biaxial Loading ◽  
Reduction Factor ◽  
Pressure Level ◽  
Weld Strength ◽  
Strain Capacity ◽  
Weld Region ◽  
Girth Welds ◽  
Tensile Strain Capacity

Abstract The ability to accurately estimate the tensile strain capacity (TSC) of a girth weld is critical to performing strain-based assessment (SBA). A wide range of geometry, material, and loading factors can affect the TSC of a girth weld. Among the influencing factors, an increase in the internal pressure level has been shown to have a detrimental effect on the TSC. The overall influence of internal pressure is usually quantified by a TSC reduction factor, defined as the ratio of the TSC at zero pressure to the lowest TSC typically attained at pressure factors around 0.5–0.6. Here the pressure factor is defined as the ratio of the nominal hoop stress induced by pressure to the yield strength (YS) of the pipe material. A number of numeric and experiment studies have reported a TSC reduction factor of 1.5–2.5. These studies generally focused on strain-based designed pipelines with evenmatching or overmatching welds, minimum heat affected zone (HAZ) softening, and a surface breaking flaw at the weld centerline or the fusion boundary. This paper examines the effects of pipe internal pressure on the TSC of girth welds under the premise of weld strength undermatching and HAZ softening. The interaction of biaxial loading and the local stress concentration at the girth weld region was quantified using full-pipe finite element analysis (FEA). The relationship between TSC and the internal pressure level was obtained under several combinations of weld strength mismatch and HAZ softening. Results from the FEA show that the effects of the internal pressure on the TSC are highly sensitive to the material attributes in the girth weld region. Under less favorable weld strength undermatching and HAZ softening conditions, the traditionally assumed reduction factor or 1.5–2.5 may not be applicable. Further, the location of tensile failure is found to depend on both the weld material attributes and the internal pressure. It is possible for the failure location to shift from pipe body at zero internal pressure to the girth weld at elevated internal pressure levels. The implications of the results for both girth weld qualification and integrity assessment are discussed.

Limit Load Finite Element Analysis of Thick-Walled Cylinders with Surface Cracks under Combined Internal Pressure and Axial Tension

2011 ◽  
Vol 341-342 ◽  
pp. 416-420 ◽  
Author(s):  
Mahdi Maarefdoust ◽  
Pooria Akbarzade
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Surface Defects ◽  
Axial Loading ◽  
Limit Load ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Applied Loading ◽  
Approximate Analytical Solutions

Limit load analysis of defect free thick walled pipes and cylinders subjected to internal pressure and combined internal pressure and axial loading is commonly performed as part of integrity assessment procedures for transmission pipelines and pressure vessels across the industry. Moreover the potential impact of environmental assisted or accidental damage that result in creation of surface defects and consequently affects the ability of vessel to withstand the applied loading conditions. This paper attempts to demonstrate the effect of surface defects on the limit load of cylinders by use of finite element method. ABAQUS software has been used for FE analysis and modeling. Approximate analytical solutions for benchmark model have been used for validation/verification of numerical results.

Influence of Girth Weld Flaw and Pipe Parameters on the Critical Longitudinal Strain of Steel Pipes

2012 ◽  
Author(s):  
Celal Cakiroglu ◽  
Kajsa Duke ◽  
Marwan El-Rich ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Tensile Strain ◽  
Critical Strain ◽  
Pipe Wall ◽  
Pipe Wall Thickness ◽  
Strain Capacity ◽  
Steel Pipes ◽  
Tensile Strain Capacity ◽  
Maximum Minimum

The design of steel pipelines against longitudinal loading induced by soil movement and temperature requires an understanding of the strain demand induced by the environment in comparison with the strain resistance of the pipes. Girth weld flaws have been identified as the potential location of failure under longitudinal tensile strains due to being the least ductile. Strain based design for the prediction of the longitudinal tensile strain capacity of steel pipes have been extensively studied by Wang, et al and included in the Canadian standards association code of practice CSA Z662.11 [1]. The extensive track record of tests have culminated into two sets of equations for the critical strain in girth welded pipes with surface breaking and buried defects as functions of the different pipe and flaw parameters. The CSA Z662.11 strain capacity equations were developed using wide plate tests with the obvious limitation of the inability to consider the effect of the internal pressure of the pipe. However, recent studies by Wang et al led to the development of a new set of equations that predict the tensile strain capacity for pipes with an internal pressure factor of 0.72. This paper analyses the two critical strain equations in CSA Z662-11 to understand the effect of different girth weld flaw and pipe parameters on the expected behavior of pipes. Also the critical strain equations developed in [2]have been analysed and compared to the equations in CSA Z662-11. Using the equations in CSA Z662-11, a 34 and 36 full factorial experimental design was conducted for the planar surface-breaking defect and the planar buried defect respectively. For the case of surface breaking defects the dependence of the tensile strain capacity (εtcrit) on apparent CTOD toughness (δ), ratio of defect height to pipe wall thickness (η), ratio of yield strength to tensile strength (λ) and the ratio of defect length to pipe wall thickness (ξ) has been studied. εtcrit has been evaluated at the maximum, minimum and intermediate values of each parameter according to the allowable ranges given in the code which resulted in the evaluation of εtcrit for 81 different combinations of the parameters. The average value of εtcrit at the maximum, minimum and middle value of each parameter has been calculated. The visualization of the results showed that η, δ and ξ have the most significant effect on εtcrit among the four parameters for the case of surface breaking defect. Similarly for buried defects the dependence of εtcrit on δ, η, λ, ξ, and the pipe wall thickness (t) has been studied. The evaluation of εtcrit for all possible combinations of the maximum, intermediate and minimum values of the 6 parameters resulted in εtcrit values for 729 different combinations. The variation of the average εtcrit over the maximum, intermediate and minimum values of the parameters showed that δ, ψ, ξ and η are the parameters having the greatest effect on εtcrit for the case of a buried defect. Further investigations could be carried out to determine suitable upper and lower bounds for the parameters for which no bounded range is defined in the CSA Z662-11 code.

Predictions of Tensile Strain Capacity for Strain-Based Pipelines With a Circumferential and Internal Surface Flaw

2019 ◽  
Author(s):  
Youn-Young Jang ◽  
Ju-Yeon Kang ◽  
Nam-Su Huh ◽  
Ik-Joong Kim ◽  
Cheol-Man Kim ◽  
...  
Keyword(s):  
Crack Resistance ◽  
Driving Force ◽  
Tensile Strain ◽  
Crack Tip ◽  
Internal Surface ◽  
Resistance Curve ◽  
Design Assessment ◽  
Crack Driving Force ◽  
Tensile Strain Capacity ◽  
Original Crack

Abstract Strain-based design assessment (SBDA) has been known for suitable assessment concept for pipelines subjected to displacement-controlled load and high plastic deformation rather than conventional stress-based design assessment. Tensile strain capacity (TSC) has been used for one of important factors to indicate limit state in strain-based design, so that it is main concern to predict accurate TSC to ensure the structural safety and integrity of pipelines. For the pipeline containing a flaw, especially a girth weld flaw, TSC based on fracture mechanics can be determined. Crack-tip opening displacement (CTOD) has been widely used for typical elastic-plastic fracture parameter, representing crack-driving force and crack-resistance curve, which are required to assess unstable crack propagation. The one of the main principles of crack assessment is that the definitions of crack-driving force and crack resistance curve should be coincident. However, there exist two kinds of the definitions of CTOD, which are based on 90° and original crack-tip concept, and these have been not unified in practical regions until now. Moreover, it is reported that the deviations of crack-resistance curve can occur in the same specimen and experiment, caused by the different definitions of CTOD. Therefore, CTOD solutions based on each of different definitions of CTOD should be highly required since inaccurate TSC would be assessed when using not the identical definition of that. In the present study, CTOD solutions of pipelines with a circumferential and internal surface flaw are suggested by using two kinds of definitions of CTOD based on 90° and original crack-tip concept. For this purpose, FE analyses were systematically carried out considering various pipe geometries and material properties. And single-edge notched tension (SENT) specimen was used for representing resistance curve of API X70/X65 material. Moreover, the effect of the choice of each CTOD definitions on TSC was investigated through crack-driving force diagram (CDFD) assessment.

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