Tension-bending analysis of flexible pipe by a repeated unit cell finite element model

In order to study the axial compressive behavior of flexible pipes, a nonlinear tridimensional finite element model was developed. This model recreates a five layer flexible pipe with two tensile armor layers, an external polymeric sheath, an orthotropic high strength tape, and a rigid inner core. Using this model, several studies were conducted to verify the influence of key parameters on the wire instability phenomenon. The pipe sample length can be considered as one of these parameters. This paper includes a detailed description of the finite element model itself and a case study where the length of the pipe is varied. The procedure of this analysis is here described and a case study is presented which shows that the sample length itself has no practical effect on the prebuckling response of the samples and a small effect on the limit force value. The postbuckling response, however, presented high sensitivity to the changes, but its erratic behavior has made impossible to establish a pattern.

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Thermal Effects on the Anchoring of Flexible Pipe Tensile Armors

Volume 5A: Pipeline and Riser Technology ◽

10.1115/omae2015-41320 ◽

2015 ◽

Author(s):

Olaf O. Otte Filho ◽

Rafael L. Tanaka ◽

Rafael G. Morini ◽

Rafael N. Torres ◽

Thamise S. V. Vilela

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Thermal Effects ◽

Current Model ◽

Element Model ◽

Small Scale ◽

Flexible Pipe ◽

System A ◽

Flexible Pipes ◽

Better Than

In the design of flexible pipes, predict the anchoring behavior on end fittings is always challenging. In this sense, Prysmian Surflex has developed a finite element model, which should help the end fitting design as well the prediction of the structural behavior and the acceptable maximum loads. The current model considers that the contact between armor-resin is purely cohesive and has been suitable for the design of end fittings [1] and [2]. But tests and new studies [3] and [4] indicate that only cohesive assumption would not be the best approach. Experimental data from prototype tests also show that the current model would not predict acceptable results for loads higher than those used in previous projects. This document will describe a study developed considering the friction and thermal contraction, instead of the cohesive phenomenon in the anchoring behavior analysis. Small scale tests were conducted in order to understand the anchoring relation between the resin and the wire used in the tensile armor. For this purpose, a special test device was developed to simulate an enclosure system. A parametric study was also performed to identify the cooling temperatures, coefficients of friction and contact properties parameters taken from small scale tests. The finite element model considers the thermal effects during exothermic curing. Using the new parameters obtained, a second model was developed. This model consists of only one real shaped bended wire inside an end fitting cavity. To validate the model, samples were tested on laboratory according anchoring design. The results of this round of tests were studied and corroborate the argument that use friction and thermal effects is better than use only the cohesive condition.

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A Study on the Response of a Flexible Pipe to Combined Axisymmetric Loads

Volume 4B: Pipeline and Riser Technology ◽

10.1115/omae2013-11384 ◽

2013 ◽

Cited By ~ 3

Author(s):

José Renato M. de Sousa ◽

Carlos Magluta ◽

Ney Roitman ◽

Tatiana V. Londoño ◽

George C. Campello

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Internal Pressure ◽

Reaction Force ◽

Experimental Tests ◽

Element Model ◽

Tension Test ◽

Experimental Results ◽

Flexible Pipe ◽

Pure Tension

In this work, the response of a 2.5″ flexible pipe to combined and pure axisymmetric loads is studied. A set of experimental tests was carried out and the results obtained are compared to those provided by a previously presented finite element model. The pipe was firstly subjected to pure tension. After that, the response to torsion superimposed with tension combined or not with internal pressure and the response to internal pressure combined with tension were investigated. In all these cases, the induced strains in the tensile armors were measured. Moreover, the axial elongation of the pipe was monitored in the pure tension test, whilst the twist of the pipe was measured when torsion was imposed and the axial reaction force was monitored when internal pressure was applied. The experimental results obtained agreed very well with the theoretical estimations indicating that the response of the pipe to tension and internal pressure is linear, whilst its response to torsion is nonlinear due to friction between layers.

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Helical Wire Behavior of Unbonded Flexible Pipes Under Bending

Volume 5A: Pipeline and Riser Technology ◽

10.1115/omae2015-41134 ◽

2015 ◽

Author(s):

Yutian Lu ◽

Huibin Yan ◽

Yong Bai ◽

Peng Cheng

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Axial Strain ◽

Bending Moment ◽

Element Model ◽

Flexible Pipe ◽

Slip Mechanism ◽

Flexible Pipes ◽

Bending Behavior ◽

Unbonded Flexible Pipes

The bending behavior of unbonded flexible pipe is governed by the response of the helical wires in the tensile armor to bending. The behavior of the helical wire, especially the axial strain, is influenced by the slip mechanism as a result of an increasing curvature under bending. In the present paper, two limit curves are considered with a certain curvature. A 3-D finite element model using ABAQUS is developed to simulate the practical behavior of the helical wires under bending. By comparing the FEA and theoretical results, a basic conclusion about the real slip path of the helical wire between two limit curves is introduced. A hysteretic bending moment-curvature relationship induced by the slip mechanism is obtained from the finite element model as well.

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Finite Element Analysis of Flexible Pipes Under Compression: Influence of the Sample Length

Volume 5A: Pipeline and Riser Technology ◽

10.1115/omae2015-42043 ◽

2015 ◽

Cited By ~ 1

Author(s):

Eduardo Ribeiro Malta ◽

Clóvis de Arruda Martins

Keyword(s):

Finite Element ◽

Finite Element Model ◽

High Strength ◽

Element Model ◽

Sample Length ◽

Flexible Pipe ◽

Element Analysis ◽

Flexible Pipes ◽

The Stability

In order to study the compressive behavior of flexible pipes, a nonlinear tridimensional finite element model was developed. This model recreates a five layer flexible pipe with two tensile armor layers, an external polymeric sheath, an orthotropic high strength tape and a rigid inner nucleus. Using this model, several studies are being conducted to verify the influence of key parameters on the wire instability phenomenon. The pipe sample length can be considered one of these parameters and its variation causes significant change at the stability response of the tensile layers. This article includes a detailed description of the finite element model itself and a case study where the length of the pipe is changed. The procedure of this analysis is here described, along with the results.

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Finite Element Analysis of Flexible Pipes Under Compression: Influence of the Friction Coefficient

Volume 5: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2016-54895 ◽

2016 ◽

Author(s):

Eduardo Ribeiro Malta ◽

Clóvis de Arruda Martins

Keyword(s):

Finite Element ◽

Friction Coefficient ◽

Finite Element Model ◽

High Strength ◽

Element Model ◽

Flexible Pipe ◽

Element Analysis ◽

Frictional Contacts ◽

Flexible Pipes ◽

Nonlinear Finite Element Model

In order to study the compressive behavior of flexible pipes, a nonlinear Finite Element model was developed. This fully tridimensional model recreates a five layer flexible pipe with two tensile armor layers, an external polymeric sheath, an orthotropic high strength tape and a rigid inner nucleus. The friction coefficient is known as a key parameter in determining the instability response of flexible pipes tensile armor. Since the featured model includes all nonlinear frictional contacts between the layers, it has been used to conduct several experiments in order to investigate its influence on the response. This article includes a description of the Finite Element Model itself and a case study where the friction between the layers of the pipe is changed. The procedure of this analysis is here described, along with the results.

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