Experimental Comparison of Tensile Armor Wires Using Strain Gages and Fiber Bragg Grating Techniques

Flexible pipes are being installed and operated in more marginal and challenging offshore conditions related to deep-water environments. Especially important is the accurate assessment of the remaining life of a flexible riser so operators can avoid costly premature change outs. So, emerging inspection and monitoring technologies are being several developed to achieve a comprehensive flexible pipes integrity approach. For unbonded flexible pipes, the primary challenges include fatigue life, collapse, axial compression loading of the tensile armor wires and end fitting development. This paper is related to end fitting development area, due to necessary folding/unfolding process on the tensile armor wires during pipe assembling. This mechanical forming generates high levels of plastic strain on the wires, which may therefore reduce the fatigue life of the flexible pipe in the field. This paper presents an analysis of the high strain level involved in the folding and unfolding process along tensile armour wire, using the strain gages and fiber Bragg grating techniques. Besides that, this paper describes a comparison analysis, which correlates the performance of both methods to assess high strain levels.

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Usability of fiber Bragg grating sensors for the fatigue life monitoring of overhead transmission lines

2018 Condition Monitoring and Diagnosis (CMD) ◽

10.1109/cmd.2018.8535970 ◽

2018 ◽

Cited By ~ 1

Author(s):

Xinbo Hang ◽

Han Zhang ◽

Yu Zhao

Keyword(s):

Fatigue Life ◽

Fiber Bragg Grating ◽

Transmission Lines ◽

Bragg Grating ◽

Fiber Bragg Grating Sensors ◽

Overhead Transmission Lines

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An Analytical Model to Predict the Bending Behavior of Unbonded Flexible Pipes

Journal of Ship Research ◽

10.5957/jsr.2013.57.3.171 ◽

2013 ◽

Vol 57 (03) ◽

pp. 171-177

Author(s):

Leilei Dong ◽

Yi Huang ◽

Qi Zhang ◽

Gang Liu

Keyword(s):

Bending Moment ◽

Bending Stiffness ◽

Nonlinear Formulation ◽

Flexible Pipe ◽

Flexible Pipes ◽

Bending Behavior ◽

Interlayer Slip ◽

Unbonded Flexible Pipes ◽

Relationship Of ◽

Theoretical Results

Analytical formulations are presented to determine the bending moment-curvature relationship of a helical layer in unbonded flexible pipes. Explicit expressions describing the variation of both bending stiffness and moment as a function of the applied curvature are given. The approach takes into account the nonlinearity of the response caused by the interlayer slip. The contribution of local bending and torsion of individual helical elements to the bending behavior of helical layers is included. Theoretical results for a typical unbonded flexible pipe using the nonlinear formulation for helical layers are compared with experimental data from the available literature. Encouraging correlations are found and the importance of the initial interlayer pressures is seen. The influence of local bending and torsion of individual helical elements on the bending behavior of the entire pipe is also evaluated. The results show that the inclusion of this local behavior significantly influences the full-slip bending stiffness.

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Temperature decoupling and high strain sensitivity fiber Bragg grating sensor

Optics and Precision Engineering ◽

10.3788/ope.20182606.1330 ◽

2018 ◽

Vol 26 (6) ◽

pp. 1330-1337 ◽

Cited By ~ 2

Author(s):

张开宇 ZHANG Kai-yu ◽

闫光 YAN Guang ◽

孟凡勇 MENG Fan-yong ◽

祝连庆 ZHU Lian-qing

Keyword(s):

Fiber Bragg Grating ◽

High Strain ◽

Fiber Bragg Grating Sensor ◽

Bragg Grating ◽

Strain Sensitivity ◽

Bragg Grating Sensor

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Qualification Approach to Unbonded Flexible Pipes With Fibre Reinforced Armour Layer

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 2 ◽

10.1115/omae2004-51175 ◽

2004 ◽

Author(s):

Jan Rytter

Keyword(s):

Offshore Structure ◽

Flexible Pipe ◽

Load Bearing ◽

Compression Load ◽

Metal Parts ◽

Analysis Tools ◽

Industry Standards ◽

Flexible Pipes ◽

Unbonded Flexible Pipes ◽

Load And Resistance Factor

The future water depth capabilities for unbonded flexible pipes is being pushed by NKT Flexibles I/S through the development of an innovative flexible pipe structure, taking full advantage of the material characteristics of metallic, polymeric and fibre reinforced materials. The fluid tight liner and possible insulation of this pipe structure are supported by an inner armour, capable of carrying the external hydrostatic pressure, clamp and crushing loads, as well as axial compression load, and an outer armour, consisting of two cross wound layers of carbon/epoxy composites, carrying the internal pressure as well as end cap forces and applied tension. A permeable and radially flexible outer layer protects the composite armour. Combining known and well-proven flexible pipe technologies and new solutions for materials, structure and functionality of the flexible pipe, positions this future product outside the present industry standards for flexible pipes, e.g. API-17J. The analysis tools used for the conventional flexible pipes are validated by NKT according to the API-17J specification. The API-17J describes load cases and corresponding allowable utilization ratios, stated as design criteria. However, this approach is not directly applicable to the composite pipe, where the same analysis tools will be used, but the material in one of the two primary load bearing layers is made of fibre reinforced polymer, a material class not covered by the API allowable utilization factors. The DNV offshore standard DNV-OS-C501 considers any offshore structure in which the load bearing material is a composite. An accompanying Recommended Practice DNV-RP-F202 for composite risers has also been issued, but is not applicable to the composite flexible pipe. The design equations of the DNV standard are formulated in the so-called Load and Resistance Factor Design (LRFD) format, where partial safety factors are applied to the load effects and to the resistance variables that enter the design equations. The DNV standard DNV-OS-C501 covers composite materials and composite metal interfaces of a structure, metal parts should be designed according to other relevant standards. The API standard can therefore be used for the metal parts. One of the challenges in using this combined approach is the different ways loads are defined in the two standards. In short, this will result in a conventional API design check of the inner armour, the polymer layers, and the secondary layers, whereas the composite tensile armour, special intermediate layers and the interfaces will be analyzed with composite specific tools based on the criteria derived from the DNV standard. The qualification procedure is described and exemplified in the following.

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Controlling Factors of Carcass Fatigue in Unbonded Flexible Pipes

Volume 5A: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2019-96310 ◽

2019 ◽

Author(s):

Upul S. Fernando ◽

Andrew P. Roberts ◽

Michelle Davidson

Keyword(s):

Fatigue Failure ◽

Failure Modes ◽

Dynamic Stress ◽

External Pressure ◽

Controlling Factors ◽

Flexible Pipe ◽

Flexible Pipes ◽

Innermost Layer ◽

Key Features ◽

Unbonded Flexible Pipes

Abstract Carcass, the innermost layer of a flexible pipe structure is designed to prevent the collapse of the pressure sheath due to external pressure. Weakness, damage or failure of the carcass layer can result in collapse with associated loss of production and potentially serious risk to pipe integrity and hydrocarbon leakage to the environment. Avoiding carcass failure in service is therefore an essential consideration during the design of unbonded flexible pipes. Carcass failure is rare in service. This paper highlights the three possible failure modes and presents further analysis on the fatigue failure mode, relevant to dynamic service. Two key features of carcass manufacture are identified as causes for dynamic stress; locking of the carcass profile due to extended pitch and polymer ingress within the carcass cavity. Guidelines for the design of carcass profiles, setting safe pitch limits and appropriate barrier profile controls to mitigate carcass fatigue failure in dynamic service are presented.

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Feasibility of Structural Health Monitoring of High Strain Rate Events Using Fiber Bragg Grating Sensors

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring ◽

10.1115/smasis2012-8039 ◽

2012 ◽

Author(s):

James Ayers ◽

Tusit Weerasooriya ◽

Anindya Ghoshal ◽

Collin Pecora ◽

Allan Gunnarsson ◽

...

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Fiber Bragg Grating ◽

High Strain ◽

Surface Strain ◽

Back Surface ◽

Bragg Grating ◽

Full Field ◽

Fbg Sensors ◽

Strain Rate Loading

Strategically located Fiber Bragg Grating (FBG) Sensors have been proposed as an in situ method to increase the signal to noise ratio (SNR) for metallic and composite components. This paper presents a systematic study that investigates the viability of FBG Sensors under high strain rate loading by initially measuring 1D-strains in a compression Hopkinson bar experiment, followed by 2D full-field strain-tensor in impact and blast experiments on plates. Specifically, high strain rates from commercialized FBG Sensors are compared to traditional resistive and semi-conductor based strain gages under various levels of 1D high strain rate loading. In the projectile-plate impact experiments, full-field back-surface strain measured using FBG Sensor arrays are compared with that measured from 3D surface Digital Image Correlation (3D-sDIC) strain measuring technique. Finally, strains in welded steel plates subjected to high explosive discharge are monitored with mounted FBG Sensors on the back surface. From this study, potential improvements in the SNR of FBG Sensors are recommended, and the survivability of these sensors under more complex, dynamic loading is evaluated.

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Experimental comparison of piezoresistive MEMS and fiber bragg grating strain sensors

2009 IEEE Sensors ◽

10.1109/icsens.2009.5398407 ◽

2009 ◽

Cited By ~ 3

Author(s):

Jacqueline Rausch ◽

Patrick Heinickel ◽

Benjamin Koegel ◽

Karolina Zogal ◽

Peter Meissner

Keyword(s):

Fiber Bragg Grating ◽

Strain Sensors ◽

Experimental Comparison ◽

Bragg Grating

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Analysis of Structural Parameters for Unbonded Flexible Pipes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.1514 ◽

2013 ◽

Vol 652-654 ◽

pp. 1514-1519

Author(s):

Zhi Bo Li ◽

Hui Xu ◽

Gui Zhen Zhang

Keyword(s):

Structural Parameters ◽

Steel Strip ◽

Complex Structure ◽

Flexible Pipe ◽

Complex Deformation ◽

Flexible Pipes ◽

Bending Behavior ◽

Unbonded Flexible Pipes ◽

Walled Cylinder ◽

Nonuniform Material

Due to the complex structure and nonuniform material of unbonded flexible pipes, an elastic thin-walled cylinder model and a helical steel strip model were established respectively to simulate different layers based on the specific structure form and parameters. Quasi-static incremental load was adopted to identify the structural parameters which had significant effects on the axial, radial and bending behavior of the pipes during the complex deformation. Sensitivity of these parameters were also analysed. The conclusion in this paper could provide guaidance for the design of unbonded flexible pipe.

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A Theoretical Approach to Predict the Fatigue Life of Flexible Pipes

Journal of Applied Mathematics ◽

10.1155/2012/983819 ◽

2012 ◽

Vol 2012 ◽

pp. 1-29 ◽

Cited By ~ 10

Author(s):

José Renato M. de Sousa ◽

Fernando J. M. de Sousa ◽

Marcos Q. de Siqueira ◽

Luís V. S. Sagrilo ◽

Carlos Alberto D. de Lemos

Keyword(s):

Fatigue Life ◽

Fatigue Damage ◽

Cross Section ◽

Time Domain ◽

Theoretical Approach ◽

Flexible Pipe ◽

Stress Effects ◽

Flexible Pipes ◽

Counting Methods ◽

Mean Stresses

This paper focuses on a theoretical approach to access the fatigue life of flexible pipes. This methodology employs functions that convert forces and moments obtained in time-domain global analyses into stresses in their tensile armors. The stresses are then processed by well-known cycle counting methods, andS-Ncurves are used to evaluate the fatigue damage at several points in the pipe’s cross-section. Finally, Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers, the effect of the annulus conditions, the importance of evaluating the fatigue life in various points of the pipe’s cross-section, and the effect of mean stresses. The results obtained suggest that the friction between layers and the annulus conditions strongly influences the fatigue life of flexible pipes. Moreover, mean stress effects are also significant, and at least half of the wires in each analyzed section of the pipe must be considered in a typical fatigue analysis.

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