Elastoplastic Analysis of the Residual Stress in Chain Links

Pacheco, Pedro Manuel Calas Lopes; Kenedi, Paulo Pedro; Jorge, Jorge Carlos Ferreira

doi:10.1115/omae2002-28083

Cited by 8 publications

(7 citation statements)

References 2 publications

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“…Previous research Many previous investigations into the behaviour of chain have considered various aspects of the strength and fatigue performance, but all in cases where the chain is not twisted [3][4][5][6][7][8][9][10][11][12][13][14] .…”

Section: 1mentioning

confidence: 99%

Predicting the Torsional Response of Large Mooring Chains

Ridge¹,

Hobbs

Fernández³

2006

Offshore Technology Conference

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe extensive use of chain as an element in multi-component moorings by the offshore industry has led to a requirement to be able to predict the torsional response of chain under a variety of service applications. Chain exhibits some interesting behaviour in that when straight and subject to an axial load, it does not twist or generate any torque. However, if chain is twisted while carrying axial load, or subjected to axial load when in a pre-twisted condition, it behaves in a highly nonlinear manner, with the magnitude of the torque dependent upon the level of twist and the axial load. Consequences of this behaviour can include handling difficulties or even a loss of integrity in the mooring system, and care must be taken to avoid problems for both the chain and any components to which it is connected.Clearly an understanding of the way in which chains may behave and interact with other mooring components (such as wire rope, which also exhibits coupling between axial load and generated torque) when they are in service is essential. Even with knowledge of the potential problems, there will always be occasions where, despite the utmost care, twist occurs. Thus it is important to be able to determine the effects, but the sizes of chain which are in use in offshore moorings (typical bar diameters are 75 mm and greater) are too large to allow easy testing at meaningful loads and there is virtually no predictive information on the torsional response of chain available in the literature.This paper addresses the issues and considerations relevant to torque in large mooring chains. The authors introduce a frictionless theory which predicts the torques and endshortening in the chain as non-dimensionalised functions of the angle of twist. The theoretical model is compared with finite element studies that include friction.Experimental data is also presented in both "constant twist" and "constant load" forms for stud-less and stud-link chains of 41 and 56 mm bar diameter. Non-dimensionalised design curves are then given for typical stud-less and stud-link chain geometries, curves which will allow a designer to estimate the torque and end-shortening for any bar diameter, axial load and twist angle combination.

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Section: 1mentioning

confidence: 99%

Predicting the Torsional Response of Large Mooring Chains

Ridge¹,

Hobbs

Fernández³

2006

Offshore Technology Conference

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“…Many previous investigations into the behaviour of chain have considered various aspects of the strength and fatigue performance, but all in cases where the chain is not twisted [3][4][5][6][7][8][9][10][11][12]. Casey [13] provides a very useful summary of the available laboratory strength and fatigue test data.…”

Section: Previous Researchmentioning

confidence: 99%

“…Casey [13] provides a very useful summary of the available laboratory strength and fatigue test data. Other authors have considered the effects of stresses and proof loading in chain with the use of finite element analysis (FEA) packages [12,14,15]. Not surprisingly, a fair amount of work seems to have been undertaken by chain manufacturers.…”

Section: Previous Researchmentioning

confidence: 99%

Torque in Mooring Chain. Part 1: Background and Theory

Hobbs

Ridge

2005

The Journal of Strain Analysis for Engineering Design

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Chain in both its forms - common (or stud-less) and stud-link - has many engineering applications. It is widely used as a component in the moorings of offshore floating systems, where its ruggedness and corrosion resistance make it an attractive choice. Chain exhibits some interesting behaviour in that when straight and subject to an axial load it does not twist or generate any torque, but if twisted or loaded when in a twisted condition it behaves in a highly non-linear manner, with the torque dependent upon the level of twist and axial load. Clearly an understanding of the way in which chains may behave and interact with other mooring components (such as wire rope, which also exhibits coupling between axial load and generated torque) when they are in service is essential. However, the sizes of chain that are in use in offshore moorings (typical bar diameters are 75 mm and greater) are too large to allow easy testing. This paper, which is in two parts, aims to address the issues and considerations relevant to torque in mooring chain. The first part introduces a frictionless theory that predicts the resultant torques and ‘lift’ in the links as non-dimensionalized functions of the angle of twist. Fortran code is presented in an Appendix, which allows the reader to make use of the analysis. The second part of the paper presents results from experimental work on both stud-less (41 mm) and stud-link (20.5 and 56mm) chains. Torsional data are presented in both ‘constant twist’ and ‘constant load’ forms, as well as considering the lift between the links.

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“…Pacheco, Kenedi, and Jorge in 2002 did a study on the elastoplastic analysis of chain links residual stress. The study describes the effect of residual stress along the links in chain during and after operations, which is important in the fatigue life of a mooring chains, [11]. Ong and Pellegrino in 2003 conducted a study of analysis in the frequency domain on the modeling of seabed interaction of mooring lines.…”

Section: Introductionmentioning

confidence: 99%

Analysis of FPSO station keeping characteristics

Obote¹,

Festus²,

Charles³

2022

Global J. Eng. Technol. Adv.

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Nowadays with increasing production and exploration activities offshore, the FPSO system has been widely adopted globally because of its unique design system and adaptability to these offshore environmental conditions. This research project aims to provide the station-keeping characteristics of an FPSO in the West African region, by analysing an FPSO with spread mooring design for multiple load cases, different offset, multiple draught conditions and environmental loads, all acting simultaneously and dynamically on the coupled FPSO system. Static and dynamic analysis were conducted using the Orcaflex software to establish the station-keeping characteristics, the recommended practices by DNV for mooring and global performance analysis were utilized for the mooring lines in the static analysis to obtain the primary equilibrium position before the dynamic analysis was conducted and to estimate a dynamic response of the risers in dynamic analysis. The effective tension of the static and dynamic analysis results for the different draught and environmental conditions shows that the far offset had the maximum effective tension, with the fully laden effective tension been the maximum effective tension of the entire simulation. The increase in effective tension as the loading of the FPSO tanks increased caused a reduction in the bending moment radius and thereby reducing the curvature of mooring lines and riser bends. But it was the near offsets that had the minimum bending radii as expected, however, from the analysis the draught conditions provided the largest responses to the multiple loading cases when compared with the changes in the offset positions.

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Elastoplastic Analysis of the Residual Stress in Chain Links

Cited by 8 publications

References 2 publications

Predicting the Torsional Response of Large Mooring Chains

Predicting the Torsional Response of Large Mooring Chains

Torque in Mooring Chain. Part 1: Background and Theory

Analysis of FPSO station keeping characteristics

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