Calculation of stress intensity factors in offshore mooring chains

Bergara, A.; Arredondo, Alberto; Altuzarra, Jorge; Martı́nez-Esnaola, J.M.

doi:10.1016/j.oceaneng.2020.107762

Cited by 11 publications

(4 citation statements)

References 14 publications

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“…One of the most critical issues in the structural integrity of floating offshore structures is the safety of mooring systems and accessories (connectors) [12][13][14][15]. Offshore mooring systems are crucial for permanently anchored floating structures in oil/gas and renewable energy applications vulnerable to corrosion-enhanced fatigue damage [16][17][18][19]. Mooring chains and accessories are subject to severe wear between links due to relative movement from waves, wind and ocean currents [20,21].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Marine Corrosion and Tribocorrosion Resistance of Offshore Mooring Chain Steel by Aluminizing Process

Alkan

2022

Brodogradnja

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The safety of mooring systems and accessories is one of the most critical issues in the structural integrity of floating oil/gas and renewable offshore structures. Mooring chains and accessories operate under dynamic conditions in harsh marine environments. They are subject to severe wear and corrosion between their links due to relative movement from waves, wind, and ocean currents that disrupt structural integrity. To cope with this problem, the pack-aluminizing process was applied on the R4 grade offshore mooring chain steel for 2 h at 850 °C to improve corrosion and wear-corrosion (tribocorrosion) resistance in 3.5% NaCl. The tribocorrosion behaviour of untreated and aluminized samples was investigated by a tribo-electrochemical setup that simultaneously allows for collecting the wear and corrosion data. Potentiodynamic and potentiostatic corrosion and tribocorrosion tests were carried out to understand corrosion kinetics. Optical, SEM, XRD and EDS analyses were performed to characterize the aluminide layer and surface morphologies before and after tribocorrosion investigations. In polarization scans under corrosion and tribocorrosion conditions, the current showed a significant activation stretch of several orders of magnitude, with minor potential changes in the anodic region. Due to the galvanic effects of sliding under natural electrochemical conditions, the untreated R4 alloy exhibited cathodic properties in the wear track, while the aluminium coating was out of the wear track due to its oxide-forming ability. At the cathodic potential, two hard Al2O3 materials under pure mechanical effects and third bodies emerging from cracks on the coating surface increase the friction coefficient (COF), while the oxide product film, which has a lubricating ability and pits which reduces the contact area, caused a decrease in COF at the high anodic potential. The study revealed that while the aluminide layer improved the corrosion and tribological character of R4 alloy, material loss from wear track increased due to micro fractures and cracks in the coating layer during sliding tribocorrosion conditions.

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Section: Introductionmentioning

confidence: 99%

Enhancement of Marine Corrosion and Tribocorrosion Resistance of Offshore Mooring Chain Steel by Aluminizing Process

Alkan

2022

Brodogradnja

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“…Okano et al [10] numerically investigated the effects of seal welding conditions, such as welding heat input, crack depth, and plate thickness on welding-induced residual stress and stress intensity factor (SIF) around the remaining crack. Bergara et al [11] calculated stress intensity factors in prospective cracks of offshore mooring chains under service conditions using the conventional finite element method (FEM) by means of contour integrals and the extended finite element method (XFEM) implemented in the Abaqus 2018 software. Hsin Jen Hoh et al [12] developed a methodology to model and calculate the stress intensity factors and weld toe magnification factors for semi-elliptical surface cracks in a circumferentially welded pipe.…”

Section: Introductionmentioning

confidence: 99%

“…There is no research on crack's influence on the sealing performance of seal rings. As for stress intensity factors at crack tip, although there are some studies on cylinders, pipes, valve body, or other simple structures [7][8][9][10][11][12][13][14][15][16][17], there is no research on crack-tip stress intensity factors of subsea connector sealing rings. In conclusion, there are two main shortages in previous research: (a) cracks' influence on the sealing performance of seal rings was not considered; (b) the crack-tip stress intensity factors study only focused on simple structures.…”

Section: Introductionmentioning

confidence: 99%

An Assessment Method of Sealing Performance and Stress Intensity Factors at Crack Tip of Subsea Connector Metal Sealing Rings

Wang

Liu²,

Zhang³

et al. 2022

Energies

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Subsea connectors are of a critical part for the sealing of subsea production systems. The working environment makes cracks initiate easily on subsea connector sealing rings. In order to ensure the safety and reliability of the sealing rings, it is necessary to study the crack’s influence on them. In this study, the main parameters that may influence stress intensity factors at crack tip are discussed. The sealing requirements of the subsea connector metal sealing rings were conducted. A finite element model was established to obtain the maximum equivalent stress and maximum equivalent plastic strain of crack-free sealing ring. Meanwhile, the influence of crack depths, crack positions, and crack angles on the sealing performance in preload and operating states was simulated through changing XFEM crack’s parameters in ABAQUS software, as well as their influence on stress intensity factors at the crack tip. The research shows that although the cracks have little effect on the sealing performance of sealing rings in the early stage, the stress intensity factors increase with the crack depths. Long-term use leads to crack propagation, structure breakage, and sealing failure. The research results are of some reference value for improving the safety and reliability of subsea connectors in practical engineering applications.

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“…En última instancia, mostraremos un análisis cualitativo fractográfico en probetas sometidas a distintos escenarios de confinamiento. SIF entre modelos numéricos para las mismas geometrías con carga axial [313]. Los efectos de la presión anular sobre el SIF son insignificantes.…”

Section: Resultsunclassified

Iniciación y propagación de fracturas en rocas shale: Influencia de las condiciones de pozo y del fluido de fractura

Antinao Fuentealba

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Desde 2010, Argentina está experimentando un aumento en la producción de recursos hidrocarburíferos no convencionales, especialmente del tipo shale, principalmente extraídos de la Formación Vaca Muerta. Una estrategia para mejorar el valor de estos recursos es a través de la transformación tecnológica, lo que requiere el desarrollo de nuevas tecnologías para mejorar el rendimiento y reducir los costos de los procesos. La producción de estos recursos requiere la fracturación hidráulica para aumentar la conductividad y la producción de hidrocarburos. Esta técnica implica inyectar grandes volúmenes de agua a altas presiones en una capa sedimentaria específica, lo que inicia y propaga fracturas bajo condiciones de triaxialidad de tensiones. La caracterización de estas fracturas es crucial para las operaciones de perforación y diseño de equipos de fracturación. Para evaluar la resistencia a la fractura, uno de los enfoques es la Mecánica de Fractura (MF). Si se considera un material elástico-lineal, la MF permite definir un factor de intensidad de tensiones K_I relacionado con la geometría y la carga, que puede medirse con probetas adecuadas o calcularse numéricamente. Cuando este factor alcanza un valor crítico K_IC comienza la iniciación y propagación de una fractura. En general, los modelos fractomecánicos ofrecen una variedad de herramientas para diferentes problemas geomecánicos, donde dos variables principales son la presencia de fluidos y las condiciones mecánicas del pozo. El objetivo de esta investigación fue desarrollar y aplicar herramientas experimentales para estudiar los mecanismos de propagación de fracturas en rocas de reservorios shale en diferentes condiciones de carga. Para ello, se aplicó una metodología experimental única, midiendo la tenacidad en probetas cilíndricas de 38 mm de diámetro, en muestras de roca ricas en carbonatos, extraídas de afloramientos de la Formación Vaca Muerta. Con un cierto arreglo geométrico y de sellos hidráulicos, el dispositivo de ensayos indujo una fuerza impulsora de naturaleza hidráulica, que causó la fractura de la muestra. Al mismo tiempo, un sistema secundario permitió transferir la presión de confinamiento hacia la probeta. El modelado fractomecánico por elementos finitos (EF) permitió analizar los sesgos experimentales asociados al cálculo de la tenacidad. Los resultados muestran que la influencia de los fluidos depende de la química del fluido de saturación y del tiempo de exposición. Muestras totalmente saturadas en soluciones acuosas conducen a reducciones importantes en la tenacidad. Contrariamente, la saturación en fluidos de base orgánica mostró una influencia despreciable en K_IC. Respecto al efecto del confinamiento mecánico, se observó un efecto significativo: los ensayos realizados a presiones de fondo de pozo (50-70MPa) condujeron a una tenacidad de la roca que duplicó la de los ensayos a presión atmosférica. A partir del análisis de la distribución de tensiones derivados de los modelos de EF y la consideración de los criterios de colapso de rocas (régimen compresivo), se discuten los posibles mecanismos de aumento de la tenacidad de la roca en condiciones de confinamiento.

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Calculation of stress intensity factors in offshore mooring chains

Cited by 11 publications

References 14 publications

Enhancement of Marine Corrosion and Tribocorrosion Resistance of Offshore Mooring Chain Steel by Aluminizing Process

Enhancement of Marine Corrosion and Tribocorrosion Resistance of Offshore Mooring Chain Steel by Aluminizing Process

An Assessment Method of Sealing Performance and Stress Intensity Factors at Crack Tip of Subsea Connector Metal Sealing Rings

Iniciación y propagación de fracturas en rocas shale: Influencia de las condiciones de pozo y del fluido de fractura

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