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Doctoral Thesis
DOI
10.11606/T.3.2007.tde-14012008-111221
Document
Author
Full name
Nelson Cárdenas Olivier
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Gonçalves, Edison (President)
Almeida, Pedro Afonso de Oliveira
Machado, Izabel Fernanda
Paes de Andrade, Arnaldo Homobono
Rangel, Angelo Gil Pezzino
Title in Portuguese
Análise de falha da camada polimérica externa de cabos umbilicais.
Keywords in Portuguese
Cabos umbilicais
Fadiga dos materiais
Imperfeições e falhas dos materiais
Polímeros (Materiais)
Abstract in Portuguese
No presente trabalho é proposto um método para estabelecer um critério de falha da camada polimérica externa dos cabos umbilicais usados em operações offshore. O método proposta baseia-se na determinação do incremento da quantidade de água absorvida pela camada polimérica externa do cabo devido à deterioração provocada pelos carregamentos cíclicos e o envelhecimento originados pelo meio marinho. Este método propõe a realização de um ensaio de fadiga à tração uniaxial no polímero que compõe a camada externa do cabo. O teste é feito simulando as solicitações a que é submetida a camada externa do umbilical durante os ensaios de fadiga feitos, segundo a norma API 17E, durante o processo de homologação do cabo. Além disso, se propõe fazer um ensaio de envelhecimento artificial no polímero da camada externa simulando as condições de serviço do cabo no meio marinho. Com o fim de avaliar a influência dos carregamentos cíclicos e o os agentes do meio marinho nas propriedades do polímero, são feitos ensaios de absorção de água segundo a norma ASTM D 570, ensaios de tração segundo a norma ASTM D 638, ensaios de dureza segundo a norma ASTM D 2240 e observações num microscópio eletrônico de varredura. Finalmente a partir do incremento de massa sofrido pelo polímero no ensaio de absorção de água foi estimado o dano no material da camada externa do cabo. Os resultados obtidos no trabalho mostraram que os carregamentos cíclicos e o meio marinho aceleraram o processo de degradação da camada polimérica externa do umbilical demonstrando assim a eficiência do método proposto.
Title in English
Failure analysis of the polymeric external layer of the umbilical cables.
Keywords in English
Aging
Damage
Failure
Fatigue
HDPE
Umbilical cable
Water absorption
Abstract in English
In the present work is proposed a method to establish a failure criterion of the polymeric external layer of umbilical cables used in offshore operations. The proposed method is based on the determination of the increment of the quantity of absorbed water by the polymeric external layer of the cable due to deterioration caused by cyclic loads and the aging process originated by the marine environment. The method proposes to carry out a uniaxial fatigue test on the polymer that composes the external layer of the cable. This test is made simulating the cyclical deformation that the external layer is submitted in the umbilical during the fatigue test done, according to the API 17E standard, during the process of cable homologation. It is also intended to make an artificial aging test in the polymeric external layer simulating the service conditions of the cable in the marine environment. In order to evaluate of the cyclical loads and the sea set aging influence on the properties of the polymer, carry out water absorption test according to the ASTM D 570 standard, traction test according to the ASTM D 638 standard, hardness test according to the ASTM D 2240 standard and observations in an scanning electron microscopy. Finally starting from the mass increment suffered by the polymer in the water absorption test it was estimated the damage in the external layer material of the cable. The results obtained in this work showed that the cyclical loads and marine environment accelerated the degradation process of polymeric external layer of umbilical cable demonstrating the efficiency of the proposed method.
 
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Publishing Date
2008-02-28
 
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