The Experts below are selected from a list of 4935 Experts worldwide ranked by ideXlab platform
Frank Y Cheng - One of the best experts on this subject based on the ideXlab platform.
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finite element modeling of Corrosion Defect growth and failure pressure prediction of pipelines
International Journal of Pressure Vessels and Piping, 2021Co-Authors: Guojin Qin, Frank Y Cheng, Peng ZhangAbstract:Abstract Corrosion Defect on pipelines shows a time-dependent growth in service environments. Prediction of Corrosion Defect growth and failure pressure of corroded pipelines as a function of time has remained a big challenge to industry. In this work, a finite element (FE)-based model was developed to quantify 3-dimensional (3-D) growth of a Corrosion Defect on an X100 steel pipe and predict the failure pressure as a function of time by considering a mechano-electrochemical (M-E) interaction. Parametric effects, including internal pressure, axial tensile stress and initial Defect length, were investigated. Distributions of von Mises stress and anodic current density (i.e., Corrosion rate) at the Corrosion Defect were determined. Results demonstrated that the growth rate of the Corrosion Defect followed the order of Defect depth > Defect length > Defect width. With increased stresses resulted from internal pressure and axial tensile loading, the maximum Defect depth and Defect length increased apparently, but the Defect width changed slightly. For example, the Defect length increased by 11% and 16% after 10 years of service at internal pressures of 18 MPa and 26 MPa, respectively, and the Defect depth increased by 27% and 34% correspondingly. However, the Corrosion width increase maintained at about 22% when the internal pressure increased from 18 MPa to 26 MPa. As the Corrosion Defect grew with time, the failure pressure of the pipeline decreased. It is expected that, upon further validation by substantial data from field and the laboratory, the developed model could contribute to improved pipeline integrity management.
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buckling resistance of an x80 steel pipeline at Corrosion Defect under bending moment
Journal of Natural Gas Science and Engineering, 2021Co-Authors: Yi Shuai, Xinhua Wang, Frank Y ChengAbstract:Abstract This work investigated the resistance of a corroded X80 steel pipe to local buckling at a Corrosion Defect under bending moment. A nonlinear finite element model was developed to study buckling behavior of the pipe and determine critical bending moment. Parametric effects, including geometry of the Corrosion Defect (shape, depth, length and width), pipe geometry (pipe outer diameter and wall thickness) and operating pressure, were determined. Results show that pipeline buckling at the Corrosion Defect depends on the Defect geometry. A rectangular Corrosion feature results in a lower buckling resistance than a semispherical Corrosion pit or a cylindrical grooved Corrosion. The depth and width of the Corrosion Defect are primarily factors affecting the buckling resistance, while the effect of Defect length is negligible. The critical bending moment to cause buckling of the pipe, i.e., the critical buckling moment, decreases as the Defect depth and width increase. The buckling resistance of the corroded pipe can be improved by increasing the pipe outer diameter and wall thickness. The role of internal pressure in buckling resistance depends on whether a constraint condition is applied at both ends of the pipe. For buried pipelines without sealing ends, the critical buckling moment decreases as the internal pressure increases.
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modeling of the mechano electrochemical effect at Corrosion Defect with varied inclinations on oil gas pipelines
Petroleum Science, 2021Co-Authors: Jinchang Wang, Zhuwu Zhang, Jiuhong Zhang, Frank Y ChengAbstract:Abstract A 3-dimensional finite element model was built to determine the effect of inclination angle of a Corrosion Defect on local mechano-electrochemical (M-E) effect in a simulated soil solution. Because of the high effect of the Defect inclination angle on the M-E effect, when the inclination angle is 0° (i.e., the primary axis of the Defect parallel to the longitudinal direction of the pipe), the greatest stress concentration level at the Defect can be observed, which is associated with the lowest Corrosion potential, the greatest anodic current density and the most serious accelerated localized Corrosion. When the inclination angle is 90°, the stress concentration level reduces and the Corrosion potential becomes less negative, accompanying with the decreased anodic/cathodic current densities. Besides, when the ratio (rca) of the primary axial length of the Defect to its secondary axial length is 1, the Defect inclination does not affect the stress and the electrochemical Corrosion rate at the Defect. With the increase of rca, the effect of the Defect inclination angle is more apparent.
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assessment by finite element modelling of the mechano electrochemical interaction at Corrosion Defect on elbows of oil gas pipelines
Ocean Engineering, 2021Co-Authors: Yi Shuai, Xinhua Wang, Junqiang Wang, Tiantian Wang, Junyan Han, Frank Y ChengAbstract:Abstract The assessment of Corrosion Defects to determine their effect on pipeline integrity is essential for pipe managers to develop a scientific maintenance strategy. In this work, a nonlinear finite element (FE) model coupled with multi-physical fields was developed to study the mechano-electrochemical (M-E) synergistic effect at an external Corrosion Defect on X100 pipeline elbow. The results indicated that bending radius has an apparent effect on the burst pressure of the corroded pipe elbow. However, anodic and cathodic reactions was insensitive to bending radius under normal working pressures. Pipes elbows with Corrosion Defects located in the intrados have a lower burst pressure than those in the extrados and central line crowns. When the deformation or stress generated at the Corrosion Defect was elastic, the synergistic mechano-electrochemical interaction effect was insignificant. However, when the depth of the Defect or the applied internal pressure of the elbow was sufficient to produce a local plastic strain in the corroded region, the Corrosion reaction of the local steel at the Defect was remarkably enhanced. Under multiaxial stress, the corrosive behaviour of steel in the Defective area involved numerous local galvanic batteries, with the anode located in the high-stress zone and the cathode in the lower-stress zone. Anodic polarisation was found to occur in high-stress zone, which accelerated local Corrosion.
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modeling of mechanical behavior of corroded x80 steel pipeline reinforced with type b repair sleeve
Thin-walled Structures, 2021Co-Authors: Yi Shuai, Xinhua Wang, Junqiang Wang, Henggang Yin, Frank Y ChengAbstract:Abstract This work investigated stress response of a corroded X80 steel pipeline repaired by a type-B sleeve to internal pressure by finite element modeling. Firstly, a three-dimensional numerical model of corroded pipeline reinforced with type-B sleeve was developed, and its accuracy and reliability were verified by the burst test results and the theoretical analytical solution, respectively. Second, the von Mises stress of the pipe body, sleeve and fillet weld was simulated under various affecting factors, i.e., internal pressure, Corrosion Defect dimension (depth, length and width) and sleeve length. Finally, a parameter sensitivity study was conducted to determine the effects of Corrosion geometry and sleeve length on the repair efficiency. The main investigation results show that the type-B sleeve repair method is effective to restore the pressure-bearing capacity of the pipeline at the Corrosion Defect, and the burst failure of repaired pipeline always occurs at the region far away from the Defect and sleeve. At the limit state of burst, the local Defective region shows the highest stress, followed by the fillet weld, and the repair sleeve has the smallest stress, thus the maximum equivalent stress of the corroded zone is suggested to be used for measuring the repair efficiency of the repaired pipe by type-B sleeve. The sleeve-repair effectiveness is affected by depth of the Corrosion Defect, a deep Corrosion Defect reduces the performance of the sleeve repair compared with a shallow Defect. The effect of the Corrosion Defect length on sleeve repair depends on the Defect depth. Furthermore, there exist a critical length of the Defect that affect the repair efficiency. The Corrosion Defect width shows limited effect on stress level at the Defect of the repaired pipe. At last, a new method based on stress analysis is proposed to optimize the sleeve length for repairing a corroded pipeline.
Yi Shuai - One of the best experts on this subject based on the ideXlab platform.
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buckling resistance of an x80 steel pipeline at Corrosion Defect under bending moment
Journal of Natural Gas Science and Engineering, 2021Co-Authors: Yi Shuai, Xinhua Wang, Frank Y ChengAbstract:Abstract This work investigated the resistance of a corroded X80 steel pipe to local buckling at a Corrosion Defect under bending moment. A nonlinear finite element model was developed to study buckling behavior of the pipe and determine critical bending moment. Parametric effects, including geometry of the Corrosion Defect (shape, depth, length and width), pipe geometry (pipe outer diameter and wall thickness) and operating pressure, were determined. Results show that pipeline buckling at the Corrosion Defect depends on the Defect geometry. A rectangular Corrosion feature results in a lower buckling resistance than a semispherical Corrosion pit or a cylindrical grooved Corrosion. The depth and width of the Corrosion Defect are primarily factors affecting the buckling resistance, while the effect of Defect length is negligible. The critical bending moment to cause buckling of the pipe, i.e., the critical buckling moment, decreases as the Defect depth and width increase. The buckling resistance of the corroded pipe can be improved by increasing the pipe outer diameter and wall thickness. The role of internal pressure in buckling resistance depends on whether a constraint condition is applied at both ends of the pipe. For buried pipelines without sealing ends, the critical buckling moment decreases as the internal pressure increases.
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assessment by finite element modelling of the mechano electrochemical interaction at Corrosion Defect on elbows of oil gas pipelines
Ocean Engineering, 2021Co-Authors: Yi Shuai, Xinhua Wang, Junqiang Wang, Tiantian Wang, Junyan Han, Frank Y ChengAbstract:Abstract The assessment of Corrosion Defects to determine their effect on pipeline integrity is essential for pipe managers to develop a scientific maintenance strategy. In this work, a nonlinear finite element (FE) model coupled with multi-physical fields was developed to study the mechano-electrochemical (M-E) synergistic effect at an external Corrosion Defect on X100 pipeline elbow. The results indicated that bending radius has an apparent effect on the burst pressure of the corroded pipe elbow. However, anodic and cathodic reactions was insensitive to bending radius under normal working pressures. Pipes elbows with Corrosion Defects located in the intrados have a lower burst pressure than those in the extrados and central line crowns. When the deformation or stress generated at the Corrosion Defect was elastic, the synergistic mechano-electrochemical interaction effect was insignificant. However, when the depth of the Defect or the applied internal pressure of the elbow was sufficient to produce a local plastic strain in the corroded region, the Corrosion reaction of the local steel at the Defect was remarkably enhanced. Under multiaxial stress, the corrosive behaviour of steel in the Defective area involved numerous local galvanic batteries, with the anode located in the high-stress zone and the cathode in the lower-stress zone. Anodic polarisation was found to occur in high-stress zone, which accelerated local Corrosion.
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modeling of mechanical behavior of corroded x80 steel pipeline reinforced with type b repair sleeve
Thin-walled Structures, 2021Co-Authors: Yi Shuai, Xinhua Wang, Junqiang Wang, Henggang Yin, Frank Y ChengAbstract:Abstract This work investigated stress response of a corroded X80 steel pipeline repaired by a type-B sleeve to internal pressure by finite element modeling. Firstly, a three-dimensional numerical model of corroded pipeline reinforced with type-B sleeve was developed, and its accuracy and reliability were verified by the burst test results and the theoretical analytical solution, respectively. Second, the von Mises stress of the pipe body, sleeve and fillet weld was simulated under various affecting factors, i.e., internal pressure, Corrosion Defect dimension (depth, length and width) and sleeve length. Finally, a parameter sensitivity study was conducted to determine the effects of Corrosion geometry and sleeve length on the repair efficiency. The main investigation results show that the type-B sleeve repair method is effective to restore the pressure-bearing capacity of the pipeline at the Corrosion Defect, and the burst failure of repaired pipeline always occurs at the region far away from the Defect and sleeve. At the limit state of burst, the local Defective region shows the highest stress, followed by the fillet weld, and the repair sleeve has the smallest stress, thus the maximum equivalent stress of the corroded zone is suggested to be used for measuring the repair efficiency of the repaired pipe by type-B sleeve. The sleeve-repair effectiveness is affected by depth of the Corrosion Defect, a deep Corrosion Defect reduces the performance of the sleeve repair compared with a shallow Defect. The effect of the Corrosion Defect length on sleeve repair depends on the Defect depth. Furthermore, there exist a critical length of the Defect that affect the repair efficiency. The Corrosion Defect width shows limited effect on stress level at the Defect of the repaired pipe. At last, a new method based on stress analysis is proposed to optimize the sleeve length for repairing a corroded pipeline.
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Modeling of local buckling of corroded X80 gas pipeline under axial compression loading
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Yi Shuai, Wang Xinhua, Y. Frank ChengAbstract:Abstract This work investigated buckling resistance of an X80 steel pipe containing a Corrosion Defect under axial compressive loading by finite element analysis. A 3-dimensional numerical model was developed to determine parametric effects on buckling behavior of the corroded pipeline. These included dimension of the Corrosion Defect (i.e., length, depth and width), pipeline geometry (i.e., outer diameter and wall thickness), internal pressure and mechanical properties of the steel (i.e., yielding strength, tensile strength and strain hardening exponent). The critical buckling load of the corroded pipeline is primarily affected by the depth and width of the Corrosion Defect, while the Defect length is the least important. As the Defect depth and width increase, the critical buckling load decreases, but the effect of Corrosion width is not apparent when the dimensionless Corrosion width w π D (w is width of Corrosion Defect and D is the pipe outer diameter) is greater than 0.5. The threshold Defect length affecting the critical axial load of the pipeline is L D t = 4.86 (t is pipe wall thickness). When L D t > 4.86 , the influence of the Defect length is ignorable. Pipeline containing a long Corrosion Defect feature of double buckling wave peaks, and a short Corrosion Defect contains a single buckling wave peak. The critical buckling load of the corroded pipeline subjected to the axial compression load increases with increased pipe outer diameter and wall thickness, but decreases with internal pressure. The increased yield and tensile strengths of the steel can improve the capacity to prevent local buckling of the corroded pipeline. The strain hardening exponent has a limited effect on the critical buckling load, which shows a significant decrease when the operating pressure is up to the critical internal pressure, resulting in yielding of the pipeline.
J.m. Hallen - One of the best experts on this subject based on the ideXlab platform.
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The negative binomial distribution as a model for external Corrosion Defect counts in buried pipelines
Corrosion Science, 2015Co-Authors: A. Valor, Francisco Caleyo, L. Alfonso, Julio Vidal, Eloy Perez-baruch, J.m. HallenAbstract:Abstract The spatial distribution of external Corrosion Defects in buried pipelines is usually described as a Poisson process, which leads to Corrosion Defects being randomly distributed along the pipeline. However, in real operating conditions, the spatial distribution of Defects considerably departs from Poisson statistics due to the aggregation of Defects in groups or clusters. In this work, the statistical analysis of real Corrosion data from underground pipelines operating in southern Mexico leads to conclude that the negative binomial distribution provides a better description for Defect counts. The origin of this distribution from several processes is discussed. The analysed processes are: mixed Gamma-Poisson, compound Poisson and Roger’s processes. The physical reasons behind them are discussed for the specific case of soil Corrosion.
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reliability assessment of buried pipelines based on different Corrosion rate models
Corrosion Science, 2013Co-Authors: A. Valor, Francisco Caleyo, J.m. Hallen, J C VelazquezAbstract:Abstract Different Corrosion rate (CR) distributions have been derived from various Corrosion growth models and used to perform reliability analyses of underground pipelines. The CR distributions considered in this work included a single-value distribution, based on the NACE-recommended CR for buried pipelines; a CR distribution derived from the Linear Growth Corrosion model; Time-dependent and Time-independent CR distributions derived from a soil Corrosion model; and a CR distribution derived from a Markov chain Corrosion model. A Monte Carlo reliability framework capable of incorporating these CR distributions has been developed and applied to both synthetic and field-gathered Corrosion data. The use of synthetic data assisted in evaluating the performance of each CR model with a consideration of Corrosion Defects of different sizes and ages. The application of the reliability framework to repeated in-line inspection data revealed the importance of careful selection of the CR distribution for an accurate assessment of the reliability of the inspected pipelines. It was shown that the best CR distribution is one that considers the ages and sizes of the Corrosion Defects as well as the observed dependence of the Corrosion Defect depth on time. Among the CRs considered in this study, the Markov chain-derived distribution was found to best satisfy these requirements.
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reliability assessment of buried pipelines based on different Corrosion rate models
Corrosion Science, 2013Co-Authors: A. Valor, Francisco Caleyo, J.m. Hallen, J C VelazquezAbstract:Abstract Different Corrosion rate (CR) distributions have been derived from various Corrosion growth models and used to perform reliability analyses of underground pipelines. The CR distributions considered in this work included a single-value distribution, based on the NACE-recommended CR for buried pipelines; a CR distribution derived from the Linear Growth Corrosion model; Time-dependent and Time-independent CR distributions derived from a soil Corrosion model; and a CR distribution derived from a Markov chain Corrosion model. A Monte Carlo reliability framework capable of incorporating these CR distributions has been developed and applied to both synthetic and field-gathered Corrosion data. The use of synthetic data assisted in evaluating the performance of each CR model with a consideration of Corrosion Defects of different sizes and ages. The application of the reliability framework to repeated in-line inspection data revealed the importance of careful selection of the CR distribution for an accurate assessment of the reliability of the inspected pipelines. It was shown that the best CR distribution is one that considers the ages and sizes of the Corrosion Defects as well as the observed dependence of the Corrosion Defect depth on time. Among the CRs considered in this study, the Markov chain-derived distribution was found to best satisfy these requirements.
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a study on the reliability assessment methodology for pipelines with active Corrosion Defects
International Journal of Pressure Vessels and Piping, 2002Co-Authors: F Caleyo, J L Gonzalez, J.m. HallenAbstract:A study on the probabilistic methodology for the estimation of the remaining life of pressurized pipelines containing active Corrosion Defects is presented. This reliability assessment is carried out using several already published failure pressure models. A steady state Corrosion rate is assumed to estimate the growth in the dimensions of Corrosion Defects. The first-order second-moment iterative reliability method, the Monte Carlo integration technique and the first order Taylor series expansion of the limit state function (LSF) are used in order to estimate the probability of failure associated with each Corrosion Defect over time. The uncertainty of the statistical variables on which the LSF depends are modeled using normal and lognormal distributions and the sensitivity of pipeline reliability to these variables is evaluated. This extended probabilistic analysis framework is applied to a sample operating pipeline which was inspected using a high resolution magnetic flux leakage inspection tool.
Guojin Qin - One of the best experts on this subject based on the ideXlab platform.
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finite element modeling of Corrosion Defect growth and failure pressure prediction of pipelines
International Journal of Pressure Vessels and Piping, 2021Co-Authors: Guojin Qin, Frank Y Cheng, Peng ZhangAbstract:Abstract Corrosion Defect on pipelines shows a time-dependent growth in service environments. Prediction of Corrosion Defect growth and failure pressure of corroded pipelines as a function of time has remained a big challenge to industry. In this work, a finite element (FE)-based model was developed to quantify 3-dimensional (3-D) growth of a Corrosion Defect on an X100 steel pipe and predict the failure pressure as a function of time by considering a mechano-electrochemical (M-E) interaction. Parametric effects, including internal pressure, axial tensile stress and initial Defect length, were investigated. Distributions of von Mises stress and anodic current density (i.e., Corrosion rate) at the Corrosion Defect were determined. Results demonstrated that the growth rate of the Corrosion Defect followed the order of Defect depth > Defect length > Defect width. With increased stresses resulted from internal pressure and axial tensile loading, the maximum Defect depth and Defect length increased apparently, but the Defect width changed slightly. For example, the Defect length increased by 11% and 16% after 10 years of service at internal pressures of 18 MPa and 26 MPa, respectively, and the Defect depth increased by 27% and 34% correspondingly. However, the Corrosion width increase maintained at about 22% when the internal pressure increased from 18 MPa to 26 MPa. As the Corrosion Defect grew with time, the failure pressure of the pipeline decreased. It is expected that, upon further validation by substantial data from field and the laboratory, the developed model could contribute to improved pipeline integrity management.
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Modeling of mechano-electrochemical interaction at a Corrosion Defect on a suspended gas pipeline and the failure pressure prediction
Thin-Walled Structures, 2021Co-Authors: Guojin Qin, Y. Frank ChengAbstract:Abstract Suspension effect poses a big threat to the integrity and safety of corroded pipelines. In this work, a finite element (FE) based multi-physics field coupling model was developed to determine the mechano-electrochemical (M-E) interaction at an external Corrosion Defect on a suspended X100 steel pipe and predict its failure pressure. Theoretical calculations were used for model validation. Parameter effects including the Defect location on the pipe, geometry of the Defect, suspension length and pipe burial depth were determined. Results demonstared that, generally, the M-E effect at Corrosion Defect caused an increased stress concentration and anodic current density (i.e., Corrosion rate), decreasing the failure pressure of the pipeline. The effect became more apparent when the pipe was in suspension. Both the stress and the anodic current density at the Corrosion Defect were dependent on the Defect geometry, especially the Defect depth. When the depth was up to 40% of pipe wall thickness, the von Mises stress exceeded the yield stress of the steel, causing local plastic deformation. A critical Defect length of 20 D t (D is the outer diameter of the pipe and t is pipe wall thickness) existed, below which the von Mises stress and the anodic current density at the Corrosion Defect increased with increased Defect length. When the Defect length exceeded the critical value, the effect was not obvious. An increased suspension length of the pipe would elevate the local stress and anodic current density at the Corrosion Defect, reducing the failure pressure of the pipe. A critical pipe burial depth of 2.5 m was identified, exceeding which the failure pressure of the pipe decreased rapidly with the increased burial depth. When the burial depth was smaller than 2.5 m, the effect was marginal. The location of the Corrosion Defect on the pipe did not affect the local stress, anodic current density and failure pressure at an appreciable level, and could be ignored in Defect assessment on suspended pipelines.
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failure pressure prediction by Defect assessment and finite element modelling on natural gas pipelines under cyclic loading
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Guojin Qin, Frank Y ChengAbstract:Abstract In this work, a 3-dimensional finite element (FE) model was developed to investigate the effect of cyclic loading, which is induced by vibration during operation of in-line inspection (ILI) tools, on local stress and strain distributions and failure pressure of an X80 steel natural gas pipeline containing a Corrosion Defect. Modelling was also conducted on a low-grade X60 steel pipe for comparison. Parametric effects, including internal pressure, R-ratio, cyclic frequency and dimension of the Corrosion Defect (primarily the Defect depth), were determined. The cyclic loading greatly increases the von Mises stress and strain at the Corrosion Defect and reduces the threshold internal pressure to cause plastic deformation at the Defect. As the internal pressure increases, both the von Mises stress and the strain increase and the high stress/strain zones expand along the Defect length direction. The local stress and strain at the Corrosion Defect increase with decreased R-ratio and cyclic frequency, resulting in a reduction of failure pressure of the pipeline. An increased Defect depth enhances local stress and strain concentrations, reducing failure pressure of the pipeline. A novel method is developed to assess Corrosion Defect during ILI tool operation and predict the failure pressure of pipelines under cyclic loading for the first time of its kind.
Y. Frank Cheng - One of the best experts on this subject based on the ideXlab platform.
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Modeling of mechano-electrochemical interaction at a Corrosion Defect on a suspended gas pipeline and the failure pressure prediction
Thin-Walled Structures, 2021Co-Authors: Guojin Qin, Y. Frank ChengAbstract:Abstract Suspension effect poses a big threat to the integrity and safety of corroded pipelines. In this work, a finite element (FE) based multi-physics field coupling model was developed to determine the mechano-electrochemical (M-E) interaction at an external Corrosion Defect on a suspended X100 steel pipe and predict its failure pressure. Theoretical calculations were used for model validation. Parameter effects including the Defect location on the pipe, geometry of the Defect, suspension length and pipe burial depth were determined. Results demonstared that, generally, the M-E effect at Corrosion Defect caused an increased stress concentration and anodic current density (i.e., Corrosion rate), decreasing the failure pressure of the pipeline. The effect became more apparent when the pipe was in suspension. Both the stress and the anodic current density at the Corrosion Defect were dependent on the Defect geometry, especially the Defect depth. When the depth was up to 40% of pipe wall thickness, the von Mises stress exceeded the yield stress of the steel, causing local plastic deformation. A critical Defect length of 20 D t (D is the outer diameter of the pipe and t is pipe wall thickness) existed, below which the von Mises stress and the anodic current density at the Corrosion Defect increased with increased Defect length. When the Defect length exceeded the critical value, the effect was not obvious. An increased suspension length of the pipe would elevate the local stress and anodic current density at the Corrosion Defect, reducing the failure pressure of the pipe. A critical pipe burial depth of 2.5 m was identified, exceeding which the failure pressure of the pipe decreased rapidly with the increased burial depth. When the burial depth was smaller than 2.5 m, the effect was marginal. The location of the Corrosion Defect on the pipe did not affect the local stress, anodic current density and failure pressure at an appreciable level, and could be ignored in Defect assessment on suspended pipelines.
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Modeling of local buckling of corroded X80 gas pipeline under axial compression loading
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Yi Shuai, Wang Xinhua, Y. Frank ChengAbstract:Abstract This work investigated buckling resistance of an X80 steel pipe containing a Corrosion Defect under axial compressive loading by finite element analysis. A 3-dimensional numerical model was developed to determine parametric effects on buckling behavior of the corroded pipeline. These included dimension of the Corrosion Defect (i.e., length, depth and width), pipeline geometry (i.e., outer diameter and wall thickness), internal pressure and mechanical properties of the steel (i.e., yielding strength, tensile strength and strain hardening exponent). The critical buckling load of the corroded pipeline is primarily affected by the depth and width of the Corrosion Defect, while the Defect length is the least important. As the Defect depth and width increase, the critical buckling load decreases, but the effect of Corrosion width is not apparent when the dimensionless Corrosion width w π D (w is width of Corrosion Defect and D is the pipe outer diameter) is greater than 0.5. The threshold Defect length affecting the critical axial load of the pipeline is L D t = 4.86 (t is pipe wall thickness). When L D t > 4.86 , the influence of the Defect length is ignorable. Pipeline containing a long Corrosion Defect feature of double buckling wave peaks, and a short Corrosion Defect contains a single buckling wave peak. The critical buckling load of the corroded pipeline subjected to the axial compression load increases with increased pipe outer diameter and wall thickness, but decreases with internal pressure. The increased yield and tensile strengths of the steel can improve the capacity to prevent local buckling of the corroded pipeline. The strain hardening exponent has a limited effect on the critical buckling load, which shows a significant decrease when the operating pressure is up to the critical internal pressure, resulting in yielding of the pipeline.
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A finite element based model for prediction of Corrosion Defect growth on pipelines
International Journal of Pressure Vessels and Piping, 2017Co-Authors: Y. Frank ChengAbstract:Abstract Growth of Corrosion Defects has been identified as the primary mechanism resulting in pipeline perforation and leaking. In this work, a finite element model was developed to simulate and predict the time-dependent growth of Corrosion Defects on pipelines in a near-neutral pH bicarbonate solution trapped under disbonded coating. The synergism of stress and local Corrosion reaction was determined quantitatively. It is demonstrated that a mechano-electrochemical effect developed at the Defect is critical to growth of the Defect, resulting in formation of a crack-like flaw at the Defect center. The time dependence of the local stress and Corrosion current density at the Defect is featured with three stages, i.e., a linear increase of local elastic stress and the negligible Corrosion enhancement under the testing condition, a slow increase of both local stress and Corrosion current density under mild plastic deformation, and a rapid increase of local stress and Corrosion current density under a high plastic deformation.
